Counter Monkey Pathfinder Session 4 Assignment

Hail and well met, welcome to Counter Monkey. I am your humble storyteller Spoony, and I am here to tell you of my own epic adventures of the past, so that you might laugh... and maybe learn.

Counter Monkey is a Web Video series hosted by Noah Antwiler, also known as The Spoony One. In this series, Spoony recounts various amusing and awesome stories from his Tabletop Game days, as well as offering helpful tips and tricks for other GMs. Also featured recordings of regular weekly Pathfinder sessions played over Skype, based on the Kingmaker adventure path and starring many of the same players from his other campaign.The name of the series comes from Spoony's days of working at a tabletop gaming store. "Counter monkey" was the employees' name for people who would hang around the front counter, tell long rambling stories about their characters and campaigns, and leave without ever buying anything.Spoony originally wanted to publish it in a book, but it later morphed into a blog (which can be found here, it also has a WordPress site) and eventually into a video series hosted on The Spoony Experiment along with his other reviews. Spoony has also mentioned hosting a weekly podcast or still trying to publish the stories, but these have not yet materialized.The series can be viewed here or here on YouTube.

Tropes:

  • Aborted Arc:
    • The Pathfinder campaign was effectively cancelled as a result of Spoony leaving Channel Awesome.
      • Even within the session this ended up happening; the character Gustave apparently had an extensive backstory along with a plotline that would involve clearing his name and avenging his family's murder. For much of the early campaign, Gustave acted as the leader of the group, and was clearly meant to be important. He ends up dying in the second session, during the fourth combat encounter the group faces, bleeding to death after being mauled by zombies.
    • The plan for Spoony's group in his Thieves' World game was for Tempus Thales to be The Team Benefactor, setting them up with missions and loot and eventually taking over the city with them and making them his lieutenants. A well-aimed flask of acid quickly derailed those plans.
      • A sequel campaign fastforwarding to the Baysib's conquest of Sanctuary was considered, but never came through due to a combination of the players going separate ways and the original campaign already having a satisfying enough conclusion.
    • The dragon scroll plot from Shadowrun: The Code got aborted when the party tripped the alarm and, rather than doing the sensible thing of grabbing the scroll and bolting, they turned it into a senselessly brutal hostage situation that ended with Spoony having to pull the Cyber Psycho Squad note  Basically, SWAT officers that have nearly lost their minds from excessive cybernetics that kill people that have. from the Cyberpunk series to wait in ambush in the sewers and kill most of them and grievously injure the rest.
  • Accidental Truth: Tandem the Spoony would boast of being 'the Greatest Swordsman in the World' just as part of his Awesome Ego character and it wasn't intended to be serious. When a sword specialist got offended by this and repeatedly got him into duels in an attempt to disprove it, though, Tandem managed to always beat his opponents by sheer luck, effectively becoming the Greatest Swordsman in the World. In the live session where he brings back the character the streak continues, all of his rolls are insanely good.
  • Actually Pretty Funny: In "The Dirtiest Book in the Game", Spoony admits that the mini-story the Book of Erotic Fantasy uses to illustrate the Lawful Neutral alignment actually made him laugh out loudnote The story has a newlywed couple discussing the Droit du Seigneur, with the young bride especially upset...and then it ends with the HUSBAND leaving in order to sleep with a noblewoman.
  • All Abusers Are Male: Accidentally averted in the Thieves' World story when Spoony misidentifies the gender (and domain) of the deity Tempus Thales is the avatar of, referring to the deity as "basically the goddess of rape and murder", who commanded Tempus to kill people and rape women to earn her favor.
  • All Men Are Perverts: A possible reason Spoony suggests for the fact that even experienced players fall for obvious traps in "Beware the Woman, For They Come From Hell".
  • Alternate Continuity: He recommends doing this for any adventure set in an established continuity, such as comic books or television shows, because the DM will be able to freely change whatever aspects of the setting they wish. This solves several problems, mainly players familiar with the work calling out the DM on fudging facts about the setting, and the DM can counter players trying to be Genre Savvy by using their knowledge of the work to influence their decisions when their characters don't know what the player knows. He notes in a game about Babylon 5 that it didn't happen often, but if a player tried to use their knowledge of the show to influence decisions, he would turn it Wrong Genre Savvy by going against their expectations.
  • Always Chaotic Evil: Any woman interested in sex, according to "Beware the Woman, For They Come From Hell." Spoony advises against running games this way, partly due to Unfortunate Implications and partly just due to how predictable it's getting.
  • And That's Terrible: After relating the tale of the Toilet Pizza: "But honestly, that was like the worst thing I've ever done to somebody... because that was horrible. That was really bad."
  • And the Adventure Continues: "Tandem's Last Ride" ends with Tandem and his party sailing off to explore unknown worlds.
  • Angrish: During the Thieves' World campaign, nemesis Tempus Thales is about to give a public address announcing a price on the party's heads, but he's still so furious over being hit in the face with a vial of acid that he winds up pacing back and forth for several minutes muttering incoherently before he can bring himself to speak.
    • This was also essentially Crazy Mike's reaction in "The Jedi Hunter" when Spoony first demonstrates the titular character's techniques via lighting his Sith Lord on fire.
  • Anti-Climax Boss: The Dragon from the D 20 Live ConBravo campaign. The DM intended for it to require an army to defeat, it was hyped up throughout the campaign, and a four player party kills it. Moreover, one of the players is incapacitated for two turns after drinking poison, and the Dragon not only fails to hit any of the players, but it ends up falling flat on its face. invoked
  • April Fools' Day: 4/1/2013 featured a video where he continues a story from a long-previous video, which turns out to just be a retelling of Army of Darkness with Spoony in the place of Ash, masquerading itself as an interview with Gary Gygax. He purposefully accentuates all the things someone could dislike about his show, he swears often and nonchalantly, he tells Oreo to be as disruptive as possible, suddenly reads from the NC-17 cut of the Zantabulous Zorcerer of Zomovie from The '80s starring David Warner as the Zorcerer, an RPG that requires owning a different, rare, expensive, and likely otherwise unrelated book, cost Spoony over 400 dollars, and has images of naked children, which he of course cannot show. He then tries to show the camera the pages tiny text, so as the audience can read it, while shaking the book. At the end he claims that Crazy Mike, the DM, died. He was struck by lightning indoors, leaving only some kind of green gelatinous blob, then leaves, saying he's going to masturbate furiously to a stuffed dog toy.
    • The moral of the story is; have a character with a high intelligence and an alchemy skill, and you can figure out the recipe for gunpowder.
  • Ascended Meme: Two years after The Squirt Gun Wars, Shadowrun 5th edition core book includes squirt guns for DMSO, as well as chemical protection modifications for armor to protect against it.
  • Attention Deficit... Ooh, Shiny!: He will often talk about something, then start going through his sourcebooks to find what he's referring to so he can show the camera, only to be distracted by something else he's seen while looking through the book and start talking about that instead.
    • He's started bookmarking topics that he plans to talk specifically to prevent this, but if something occurs to him mid-episode he will still take some time searching for it.
    • Taken even further in his Epic Rant. As the title implies, it's a meandering (but entertaining) four part mess of topics, starting off as a discussion of super hero role-playing games, then going on to discuss things like Call of Cthulhu or Babylon 5, ending on Spoony talking about a video game based on The Lord of the Rings.
  • Author Vocabulary Calendar: Spoony really likes quoting the phrase "become king by his own hand" from the ending crawl of Conan the Barbarian.
  • Awesome, but Impractical
    • In Age of Manure, Spoony warns against specializing in exotic weapons, as most DMs will not think to have things like Halberds, Nunchucks, Double Hammers, or similar as loot at the end of a dungeon.
    • In "Dem Bones" he notes that some dice may look cool, but rolling with them is detrimental to gameplay due to them being hard to read or being shaped in a way that they don't roll properly.
  • Awesome Mc Coolname: In "The Age of Manure", Bennett the Sage says that the D&D character he played when he was 13 was named ScytheGoemon.
  • Awesomeness Is Volatile: In "Dem Bones" he relates the story of a player who rolled an oversized D20 die that rolled to a stop and then split apart. The DM didn't see the number but pronounced it a crit, because "if you roll so hardcore the die explodes, it's a crit!"
  • Badass Decay: In-Universe, Spoony criticises DMs who don't play monsters intelligently from the POV of the monsters in "Circle Strafe". When DMs don't play them intelligently from the POV of the dragon, instead just doing it to provide an encounter for a party in a way that lets them all attack the dragon and often weakens the dragon in other ways. Spoony believes a dragon should always be a Final Boss and shouldn't be degraded in this way.
  • Badass Normal: In "The Jedi Hunter", he recounts when he joined a Star Wars game, but didn't want to be a Jedi like everyone else. So he thought about what a non-Force-sensitive character could do to fight someone like Darth Vader who can deflect blasters and similar weapons with lightsabers and the Force (Spoony notes that this was before the prequel movies came out, so many pieces of media like Knights of The Old Republic that nowadays show how to beat a Force-Sensitive didn't exist yet). He reasoned that the best strategy would be to use weapons that Jedi can't block or deflect, as well as rely on the predictability of the other players and the DM, Crazy Mike, in the Force skills they likely haven't taken. In the end he created a Jedi hunter armed with dual armor-mounted flamethrowers, an armor-mounted electric net launcher (the net being capable of knocking people unconscious), a deck-clearing blaster (which he describes as a blaster shotgun), smoke and stun grenades, andhe's rigged the hallways of his ship with explosives. He deals a Curb-Stomp Battle to two Sith Lords, blows up a third, and completely incapacitates Sith and Jedi alike at once, pissing off DM Crazy Mike with his antics. He also had additional weapons that he'd utilize in later fights, including spore-based tear-gas grenades that had a small percentage to kill instead of stun.
  • Balance Between Good and Evil: Deconstructed in Laundry Day at the Tower of High Sorcery, wherein Spoony expresses confusion over why anyone would devote their live to maintaining neutrality. His argument is basically that if you consider keeping the balance to be a desirable thing, doesn't that make acting to keep it a good act in your eyes, and therefore you should view yourself as good?
  • Balance of Power: In "Vampire: Spoony's Jyhad", the Lancea Sanctum and the Invictus formed this in the LARP, with the other factions either too small to pull anything (Circle of the Crone) or lone stragglers forced to join their ranks (Ordo Dracul and Carthian Movement). By the time Spoony joined, they had stopped doing weapon checks altogether, confident that nobody would pull a stunt or upturn the system...
  • Baleful Polymorph:
    • The players of "Vegan Steve & The Djinni of Jengai Fomogo" sought the eponymous Djinni to wish away a curse that would turn them into beasts.
    • Manure golems in "Age of Manure" turned everything they touched into manure (or fellow Manure Golems, post-edit).
  • Ban on Politics: Spoony says that if political conversations start in the games he runs, he flat out orders the players discussing it to stop, since those things rarely end well.
  • Batman Gambit: In "Die a Hero & Die Long Enough to See Yourself Become the Villain," how Strahd manipulated Sir Stark (Spoony's paladin) into working for him, playing the To Be Lawful or Good card by reminding him that innocents will die if he didn't act.
  • Bavarian Fire Drill: Encouraged in "The Bardic Knock Spell" as a way to get past obstacles without resorting to violence or sneaking. Comes with a warning that the DM will probably only let you get away with it once.
  • Berserk Button:
    • Spoony attests that stealing from the party is so effective a button it can work as a railroading device; it doesn't matter how inconsequential or cheap the items stolen were, the party will probably be furious and want to track the thieves down so badly they'll follow whatever lead the DM gives them.
    • Spoony promises that he will leap across the table and strangle you with your own lungs if you bring hard-to-read dice to his table.
    • He gets really angry with people who complain about dice rolls when determining stats, saying the numbers for stats are not what make a good character. "3d6 in Order" is all about how much it bugs him, along with a demonstration of a book that can make a good character build without relying on the stats.
  • Beware the Nice Ones: "Vampire: Spoony's Jyhad". Victory for the Carthians, bitch.
  • Big "OMG!": In Shadowrun: The Code, Spoony replicates his reaction to the Villain ProtagonistStupid Crooks deciding to Prove I Am Not Bluffing.
  • Bleached Underpants: In "The Dirtiest Book in the Game" (discussing the Book of Erotic Fantasy), Spoony points out that while the list of adventure hooks all have something to do with sex, they're fairly mature and seriousnote except maybe for the one where a sorcerer hires the party to retrieve his stolen pleasure golem, which Spoony says could make for a good comedy plot and not at all explicitly pornographic, and thus could be easily be used in a "vanilla" campaign.
  • Boring, but Practical:
    • In Age of Manure, Spoony warns against specializing in exotic weapons, it's better to go with swords, daggers, bows or similar "boring" weapons because DMs will use magical or enhanced versions of those as loot at the end of the dungeons.
    • In "Don't Be That Guy" and other videos, he says it is the simplest thing in the world to carry a club, it's a big wooden stick, even a tree branch lying around can be a club. But you'd be amazed how often it comes in handy, especially if skeletons show up.
  • Born Lucky:
    • Vegan Steve. Out of a shuffled Deck of Many Things that has 11 good cards and 11 bad cards, he draws 11, and the first 10 are all good cards.
    • Spoony himself when playing his bard character Tandem the Spoony, as seen in "Tandem's Last Ride" and "The Greatest Swordsman in the World" (at the start of the D 20 Live ConBravo segment - or, for that matter, the ConBravo campaign itself). He consistently wins battles that on paper he would be expected to lose, just because his rolls are always so good and the enemy's are so bad.

      Big Mike:note The DM of the ConBravo campaign, after describing a critical hit where Tandem stabbed the dragon in the spine. What is it with you and your fucking character?

    • Spoony proves himself to be this again in Nightstake, when he rolls straight 10s on 6 10-sided dice to stake Invisible Jason's AssamiteNinja vampire with Celerity through the chest with a thrown sharpened police nightstick; the odds of this succeding being literally Million To One

      Assamite: *staring down at the nightstick poking out of his chest* Fuck, that was lucky.

  • Born Unlucky:
    • The "Botchamania" video features an entire Spycraft party whose attempts to board a train resulted in two team members dying thanks to their rolling several Critical Failures in succession. And this was even with Spoony trying to help them out by fudging things in their favor, giving them extra chances to succeed, etc.
    • Spoony's friend Crazy Mike, who failed to connect a to-hit roll in two months, and that's while Dual Wielding, which doubled his number of to-hit rolls.
    • The Black Dragon Final Boss from the ConBravo D 20 Live 2012 game. First he misses with his breath weapon, misses his bite, misses one claw attack, critically fails with the other claw and then collapses face first onto the ground, while the party kills by hacking away at its spinal cord.

      Big Mike:note After Linkara elects to follow Spoony's lead and attack the dragon's spine. I am the unluckiest dragon in the world. I had cannons shot at me and now everyone's hitting my spine!

    • Similarly, Linkara botches almost every roll in the D20 Live session.
  • Bragging Rights Reward: The only conceivable reason Spoony can derive for a minotaur player disregarding the tenet of "Thou Shalt Not Fuck With the Lady of Pain."
  • Break the Cutie: Vampire: Spoony's Jyhad really reads like this, both for his character and him as a player. He played a Carthian with poor combat but good utility skills so as to be a friendly, helpful character, in hopes of socializing more with the other LARPers. When his character is jumped and kidnapped, he's actually optimistic and excited about it, thinking this was a special adventure for the newbie, having previously been worried about being ignored as a side character. His hopes are then crushed as his character is tortured with a blow torch and made a slave of the much less friendly vampires that make up the bulk of the LARP, and he proceeds to bomb them all to hell in revenge. Spoony admits he reacted poorly to the railroading, though still considers them to have been out of line.
  • Brick Joke: In the ConBravo 2012 D 20 Live game, Spoony's character makes sure to steal a bunch of glasses from his employer, crush it and put it in a bag, before his party goes on their mission. Later, when they encounters an ogre-like beast, Spoony's character shoves the team's tank out of the way to attack the monster, with the sack of crushed glass to the face.
  • Bullying a Dragon/Did You Just Flip Off Cthulhu?: In the ConBravo D 20 Live game, the party eavesdrops on a massive, but wounded, black dragon. And as it begins to fly away.

    Spoony:Excuse me... Seven hells you're one ugly lizard... Hey, yo, Puff! Why don't ya come down here and see what a real man's made of? If... you've got the guts.

    • Essentially what the Minotaur player was trying in "Don't Fuck With The Lady of Pain".
    • Spoony advises against players doing this to the DM. If the player pointedly tries to make the DM angry, or to derail the story, or plays in a way that they know annoys them, the DM will start to fight back, and they will win. By contrast, playing cleverly and intelligently but going along with the story and having fun will make the DM happy that their campaign is being enjoyed, and they will repay the kindness if the players need it by helping them out or sending good loot their way.
  • But Thou Must!/Stupidity Is the Only Option: Discussed in "Beware Women For They Come From Hell", when he says that even if a player knows that any food they're offered in the game is poisoned, getting on the boat will result in being attacked by aquatic monsters, and that the woman giving them the quest will turn out to be evil, they still have to go along with it because otherwise the adventure would end there.

    Spoony:There's a point where you have to ask yourself, "do you want to play D&D or not?"

  • Butt-Monkey: Jinx the gnome druid in the Pathfinder campaign, as played by Pushing Up Roses, on account of the character having an intelligence score of 9.
  • Catch-Phrase:
    • When something bad happens; "You're fucked! You're just fucked!"
    • When a player or DM makes poor gaming decisions; "By the way, if you're <that thing>, you're doing it wrong."
    • Describing a character with an unconventional play style as "Not that kind of (X)."
  • The Cavalry Arrives Late: Tempus Thales in the Thieves' World campaign. He was intended to serve as reinforcements for the heroes, only for the heroes to win the battle before they arrive. Consequently, the heroes mistake his audible approach to be reinforcements for the cultists they just defeated, and... well...
  • Cavalry Betrayal: Inverted. In the Thieves World campaign, the players mistook the sound of the cavalry to that of their enemies and reacted as such, unwittingly inflicting Facial Horror on their employer and running the campaign Off the Rails.
  • Character Alignment: Naturally, he repeatedly discusses alignments.
    • "The Prisoner Dilemma" is an hour-long discussion of this, starting off with the titular dilemma: after massacring their way through a cave of orcs, the heroes find a bunch of orc women with orc babies, and their guards throw down their weapons and surrender. What do you do with them? Let the arguments begin.
      • invoked Other topics in the video include ways to interpret alignment (Spoony notes he had a Lawful Good villain in a campaign who acted like a Knight Templar), why characters of conflicting alignments might disagree and possible solutions, how strictly a DM may make players adhere to their alignments, and more. He mentions that alignments are both the best and worst part of D&D.
    • invoked In another video, he discusses his dislike for the Chaotic Neutral alignment. A Chaotic Neutral character has no regard for good or evil, no respect for law and authority, and will do what they want, when they want, for whatever reason they want. For this reason he feels Chaotic Neutral is a cop-out alignment for players who want free reign to do as they like without having to get into an alignment argument.
    • invoked "Where Have All the Lawful Goods Gone?" is, naturally, about the Lawful Good alignment. Spoony relates how he really doesn't like people who think playing a Lawful Good character automatically means being Lawful Stupid, saying that you can "just play a Paragon", and you've got the right idea.
  • Chunky Salsa Rule: He mentions this trope in the Thieves World video, when describing his thought process during the aftermath of the acid-in-the-face incident. The example he uses is that if your jugular vein is cut, it will most likely be fatal regardless of how many hit points you have or how much damage the cutting weapon normally does. This reasoning, combined with the fact that it's very much in character for the god Tempus is the avatar of to refuse to heal him if he gets utterly humiliated in battle, caused Noah to ultimately decide that that flask of acid to the face, which would normally do trivial damage to somebody as high level and overpowered as Tempus Thales, would instead horribly disfigure him, cause him immense pain, and change the course of the entire campaign.
  • Cliffhanger: Part one of the "Apocalypse Stone" episode literally ends mid-sentence, and that sentence is "This is kinda where the story really gets interesting..."
  • Cloud Cuckoo Lander: Gary, who knew the game's rules but never could show up on time for any number of reasons, including one occasion where he left the house, then realized he forgot to put on pants.
  • Cold-Blooded Torture/Jack Bauer Interrogation Technique: In "Shadowrun: The Code", one of the players takes a guard who lost his leg to another PC's Dragon's Breath rounds and punches him in the wound while demanding information. Needless to say, Spoony was horrified.
  • Combat Pragmatist: "Circle Strafe" covers how various enemies, particularly dragons, would and possibly should use their natural advantages or intelligent tactics. Why let Conan whack you in the shins when you can circle overhead and blast the party with your breath weapon, particularly those pesky ranged combatants? Other thoughts include lizardmen attempting to sink a boat instead of board it, and hobgoblins (who are military-grade combatants) using such formations as a phalanx or a shield wall.
  • Conscience Makes You Go Back: He expects this of players who are playing evil-aligned characters. Even if a character would normally run off and leave people for dead, Spoony wants them to have "that moment" when they have a moral epiphany, turn around and go help the party. In a similar vein, he wants evil-aligned characters giving their party an assurance that "I'm going to be evil except to you guys."
  • Cool vs. Awesome: Discusses this as the big draw of the Cyberpunk spin-off Cthulhupunk. In the usual Cthulhu stories, weapons are of course useless against a Great Old One, but that's in the early 20th century, while Cyberpunk is in the 21st century. What happens when all the enhanced cybernetics, energy weaponry, genetics research, and other technological advances of the time are used by characters to battle a Great Old One? Only one way to find out, but whatever the outcome it's going to be badass.
  • Corpsing: Despite not being scripted, Spoony still does this. He even anticipated it during the review of "The Book of Erotic Fantasy", and he certainly couldn't stop chuckling when describing the "Rod of the Erotic Body".
    • In the "Age of Manure" video, you can hear Spoony's brother Miles (presumably operating the camera) start laughing when Spoony acts out Hinsty David's creation of the Manure Golem (specifically, right after he says "Look what I did!").
  • Corrupt the Cutie: Sir Stark, Spoony's paladin in "Die a Hero & Die Long Enough to See Yourself Become the Villain", suffered from this when Strahd gradually manipulated him through Batman Gambits and playing the To Be Lawful or Good card over and over, gradually turning Sir Stark into his equivalent of Darth Vader (though Spoony didn't describe any evil acts Stark did).

Abstract

Background

Can non-human animals comprehend and employ symbols? The most convincing empirical evidence comes from language-trained apes, but little is known about this ability in monkeys. Tokens can be regarded as symbols since they are inherently non-valuable objects that acquire an arbitrarily assigned value upon exchange with an experimenter. Recent evidence suggested that capuchin monkeys, which diverged from the human lineage 35 million years ago, can estimate, represent and combine token quantities. A fundamental and open question is whether monkeys can reason about symbols in ways similar to how they reason about real objects.

Methodology/Principal Findings

Here we examined this broad question in the context of economic choice behavior. Specifically, we assessed whether, in a symbolic context, capuchins' preferences satisfy transitivity - a fundamental trait of rational decision-making. Given three options A, B and C, transitivity holds true if A≥B, B≥C and A≥C (where ≥ indicates preference). In this study, we trained monkeys to exchange three types of tokens for three different foods. We then compared choices monkeys made between different types of tokens with choices monkeys made between the foods. Qualitatively, capuchins' preferences revealed by the way of tokens were similar to those measured with the actual foods. In particular, when choosing between tokens, monkeys displayed strict economic preferences and their choices satisfied transitivity. Quantitatively, however, values measured by the way of tokens differed systematically from those measured with the actual foods. In particular, for any pair of foods, the relative value of the preferred food increased when monkeys chose between the corresponding tokens.

Conclusions/Significance

These results indicate that indeed capuchins are capable of treating tokens as symbols. However, as they do so, capuchins experience the cognitive burdens imposed by symbolic representation.

Citation: Addessi E, Mancini A, Crescimbene L, Padoa-Schioppa C, Visalberghi E (2008) Preference Transitivity and Symbolic Representation in Capuchin Monkeys (Cebus apella). PLoS ONE 3(6): e2414. https://doi.org/10.1371/journal.pone.0002414

Editor: Laurie Santos, Yale University, United States of America

Received: April 7, 2008; Accepted: April 23, 2008; Published: June 11, 2008

Copyright: © 2008 Addessi et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Funding: Funded by VI Framework, NEST Pathfinder Initiative, What it means to be human, Contract n° 12984, Stages in the Evolution and Development of Sign Use - SEDSU, and Contract n° 29088, Humans: The Analogy-Making Species - ANALOGY. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Competing interests: The authors have declared that no competing interests exist.

Introduction

Humans have been defined “the symbolic species” since the use and understanding of symbols drastically transformed our hominid ancestors throughout evolution [1]. The acquisition of a complex language is unparalleled in the animal realm and probably underlies human uniqueness [2]. Besides language, humans creatively and flexibly use a huge array of symbols, thus acquiring information about the world without having direct experience of all its features. The use of symbols makes it possible to travel both in time and space and to accumulate and transmit cultural knowledge over generations [3]–[5].

Whether non-human animals comprehend and employ symbols is still an open question since symbolic competence is difficult to test in the absence of language. The most convincing empirical evidence of animals using symbols comes from a series of studies on language-trained apes. Two chimpanzees learned to use lexigrams to ask one another's for the appropriate tool required to obtain food and they readily fulfill to one another's requests [6]. Moreover, chimpanzees trained to sort out real foods from real tools and to categorize each of them by choosing the consistent lexigram out of two (generically indicating one ‘food’ and the other ‘tool’) kept categorizing using the correct lexigram also when presented with new items [7], [8]. Furthermore, in a reverse-reward contingency task [9]–[11], where chimpanzees failed to select a smaller food array in order to receive a larger one, the use of Arabic numerals (instead of food) allowed chimpanzees to overcome their strong motivation to choose the largest between the two food arrays and to be successful.

Little is known about the symbolic ability of non-apes. There is some evidence that capuchin monkeys, South-American primates that diverged from us 35 million years ago, use tokens as symbols [12], [13]. Tokens are inherently non-valuable objects that acquire an associative value upon exchange with the experimenter [14]. Following DeLoache's [5] definition of symbol (“something that someone intends to represent something other than itself”, p.66), a token can be considered a symbol since it is arbitrarily related to its referent through the conventions established between the experimenter and the exchanging subject [15], [16].

Numerous studies in recent years examined aspects of economic behavior in non-human primates using tokens. For example, tokens were used to test reactions to social inequity [17, but see 18,19], reference-dependent preferences [20], and endowment effects [21]. In all these experiments, monkeys were typically asked to trade with the experimenter valueless objects (the tokens) in exchange for desirable pieces of food. Probing economic preferences using tokens opens a number of important questions. For example, monkeys could psychologically treat tokens as symbols for the food they represent, similarly to how humans treat words or money. Alternatively, exchanging tokens for food could simply result from instrumental conditioning. In this scenario, monkeys exchanging tokens with the experimenters would display a behavior conceptually analogous to the behavior of pigeons operating a lever to obtain food.

A closely related question is whether preferences monkeys reveal by the way of tokens are qualitatively and quantitatively similar to those they reveal when they choose between the actual foods. To examine this issue, we adopted a behavioral paradigm that provides a measure of the value capuchins assign to different foods. Subjects choose between two foods, one of which is preferred, offered in variable amounts. When offered the choice between a unit quantity of each food, subjects choose (by definition) the preferred food. However, if the less preferred food is offered in sufficiently large amounts, subjects will choose it. The relative value of the two foods can be inferred from the indifference point—the quantity ratio for which the subject chooses either food equally often [22]–[24]. Qualitatively, this behavioral paradigm highlights two fundamental traits of economic choice behavior. First, individuals have strict economic preferences: away from the indifference point, their choices are typically very consistent. Second, individuals' choices satisfy transitivity. In other words, if an individual is indifferent between foods X and Y and if it is indifferent between foods Y and Z, the individual is also indifferent between foods X and Z. Quantitatively, this behavioral paradigm provides an operational measure of the value individuals subjectively assign to different foods.

Transitivity is one of the main axioms of standard economic theory and is a fundamental trait of rational decision-making [25], [26]. Only a few studies examined preference transitivity in non-human primates. At the behavioral level, both capuchins and rhesus macaques (Macaca mulatta) combine the relative value assigned to three foods (or juices) according to transitivity [23], [24]. Furthermore, when rhesus macaques are presented with binary choices between two types of juice in variable amounts, neurons in the orbitofrontal cortex encode the value of the offered and chosen juices in a menu invariant way, suggesting that preference transitivity might be rooted in the activity of these neurons [23].

In this study, we compared preferences revealed in the real (food) and in the symbolic (token) conditions. We trained five capuchins to associate three different foods with three different types of tokens. In separate sessions, we then presented monkeys with pair-wise choices between actual foods (Food condition) or between tokens associated with the same foods (Token condition). Finally, we compared the relative values measured using tokens with those measured with the actual foods. Notably, the cognitive demands of this situation are much more challenging than in previous studies carried out in capuchins [12], [13]. Indeed, in order to choose between different quantities of tokens corresponding to qualitatively different foods, capuchins should recall the association between each token and the corresponding food, evaluate the amount of each token array, estimate the relative value of the two offers, and finally make up their mind on which option to choose. We envision three possible results. One possibility is that capuchins use the same cognitive mechanism to reason on tokens as they do with food; as a consequence, their performance will not differ in the two contexts. Alternatively, capuchins could find it more difficult to deal with tokens than with food; thus, their choice pattern will be more consistent with transitivity with food rather than with tokens. Finally, tokens may aid capuchins to override the incentive value of the immediately available food, as described for chimpanzees [9]–[11], and to achieve psychological distancing (i.e., to separate cognitively from the immediate behavioral environment, thus directing attention away from the salient features of the stimulus, 27–30). If this were the case, capuchins would deal with tokens better than with food, and therefore their choice pattern will be more consistent with transitivity with tokens rather than with food.

Results

Five captive-born capuchin monkeys were individually tested. Each subject was presented with a “choice apparatus”, constituted by a platform with two sliding trays where different quantities of food or tokens (according to condition) were available (Figure 1). The subject could choose one of the two offers (by pulling one of the two sliding trays) on the basis of the amount of food or tokens presented. In the preliminary phase, subjects were offered pair-wise choices between two foods (A:B and B:C) in order to select three foods such as A was preferred to B, and B was preferred to C. Then, in the Food condition, preference transitivity was tested by presenting capuchins with binary choices between different quantities of the three foods, labeled A, B and C in decreasing order of preference (Table 1, Video S1, S2, S3, S4). Subsequently, in the training phase, subjects learned to exchange three valueless tokens for the three types of food used in the Food condition (Table 2). Finally, in the Token condition, preference transitivity was tested by presenting capuchins with binary choices between different quantities of the three tokens, labeled A, B and C in decreasing order of preference (Table 1, Video S5, S6, S7, S8, S9, S10). In each trial, after choosing an offer type capuchins were required to exchange the token(s) selected (one at a time) before the experimenter administered the next trial. Each token exchange took a few seconds and it was rewarded with one piece of food.

Figure 1. Experimental apparatus.

The apparatus is positioned in front of the indoor compartment and the experimenter is nearby the apparatus, facing the subject. The subject can reach each tray through the corresponding opening in the wire mesh (8.5 cm×3.8 cm each). This photo depicts Robot, a male capuchin, who has just selected three black plastic tokens (each corresponding to one piece of dried apricot, food C) preferring them to one brass hook (corresponding to one cheerios, food A). Robot is exchanging the first plastic token for one piece of dried apricot.

https://doi.org/10.1371/journal.pone.0002414.g001

Both in the real (food) and in the symbolic (token) conditions, the quantities of the two items offered to the monkey for any given item pair varied from trial to trial (Table 1). We thus obtained in each session three choice patterns corresponding to the three item pairs. In the Food condition, capuchins generally had strict economic preferences (i.e., for offer types away from the indifference point, data points were close to 0% or 100%). Figure 2 shows the behaviour recorded in a representative session in the Food condition. To compute relative values, we fitted each choice pattern with a “normal sigmoid”, and we interpreted the underlying Gaussian as a distribution for the relative value. The mean (μ) and variance (σ2) of the distribution thus represent the estimate for the relative value and the relative error of measure (see Methods for details).

Figure 2. Food condition.

The three panels show the choice patterns recorded for food pairs A:B, B:C and A:C, respectively. In the first panel, the x axis represents the offer type, and different offer types are ordered by the ratio of qB / qA, where qA and qB are the quantities of foods A and B offered to the subject. The y-axis represents the percentage of trials in which the subject chose item B. Analogously, in the second and third panel, the y-axis represents the percentage of trials the subject chooses food C. In this session, the subject is offered cheerios as food A, dried pineapple as food B, and rice krispies as food C. The sigmoid fits provide the relative values V(A) = 0.9 V(B), V(B) = 2.4 V(C), and V(A) = 2.2 V(C); therefore, subject's choices satisfy value transitivity since 0.9 * 2.4 ∼ 2.2.

https://doi.org/10.1371/journal.pone.0002414.g002

In all sessions but one, we could evaluate the relative value of each food pair (see below). As shown in Figure 3, in 96% of these sessions (23 out of 24 sessions), measured relative values satisfied value transitivity (z-test, p>0.05). This held true for all subjects, i.e. Gal (5/5 sessions), Paprica (5/5 sessions), Robot (4/5 sessions, in one session we could not evaluate the relative value of the A:C food pair), Sandokan (5/5 sessions), and Carlotta (4/5 sessions, in one session her behavior was not consistent with transitivity; p = 0.03). For all subjects but Robot, the first session of the Food condition was always consistent with transitivity.

Figure 3. Food condition.

The x-axis represents the product nA:B* nB:C, the y-axis represents nA:C, and each data point represents one of the 24 sessions consistent with value transitivity.

https://doi.org/10.1371/journal.pone.0002414.g003

In the Token condition, in 13 out of 25 sessions we could not evaluate the relative value of at least one of the three pairs because the subject consistently chose one of the two types of token. Figure 4 shows the behavior recorded in one of the sessions in which we could not evaluate the relative value of the A:C token pair. In the remaining 12 sessions, we could evaluate the relative values of all the three token pairs and capuchins generally had strict economic preferences. As shown in Figure 4, in all these 12 sessions measured relative values satisfied transitivity (z-test, p>0.05). In particular, this held true for four out of five subjects, i.e. Gal (5/5 sessions), Paprica (4/5 sessions), Robot (2/5 sessions), and Sandokan (1/5 sessions); for all the above subjects, the first session of the Token condition was always consistent with transitivity.

Figure 4. Token condition.

The three panels show the choice patterns recorded for token pairs A:B, B:C and A:C. Here the subject is offered green chips as tokens A (corresponding to one cheerios each), black plastic tubes as tokens B (corresponding to one piece of dried apricot each), and brass hooks as tokens C (corresponding to one sunflower seed each). The sigmoid fits provide the relative values V(A) = 2.8 V(B) and V(B) = 4.3 V(C); however, when facing the choice between one token A and up to six tokens C, this subject always chose the single token A, thus we could not evaluate the relative value of A vs. C.

https://doi.org/10.1371/journal.pone.0002414.g004

To compare the results obtained in the Food condition and in the Token condition, we performed a repeated measures MANOVA (including sessions where it was possible to evaluate the relative value of each item pair, N = 24 in the Food condition and N = 12 in the Token condition) . The results showed that there was no significant relationship between the estimate of the relative value and its variability, corresponding respectively to the mean and variance of the Gaussian distribution (F2,2 = 11.65, p = 0.08, η2p = 0.92). The relative value was significantly higher in the Token condition than in the Food condition (F1,3 = 12.35, p = 0.04, η2p = 0.80), whereas the variability in capuchins' performance did not significantly differ across conditions (F1,3 = 3.51, p = 0.16, η2p = 0.54).

Discussion

Our results can be summarized as follows. Qualitatively, preferences revealed by the way of tokens were similar to those measured with the actual foods. Specifically, when choosing between tokens, capuchins displayed strict economic preferences and choices satisfied transitivity since the first session for all subjects but one. These results confirm and extend previous findings obtained in non-human primates faced with choices between real foods or juices [23], [24] and with relative numerousness judgments between food or tokens [13]. Quantitatively, however, values measured by the way of tokens differed systematically from those measured with the actual foods. In particular, for any pair of foods, the relative value of the preferred food tended to increase when monkeys chose between the corresponding tokens. As a consequence, while in the Food condition it was generally possible to assess the relative value of the items, in about half of the sessions carried out in the Token condition this was not the case. The fact that choice patterns were otherwise qualitatively similar in the two conditions suggests that by increasing the number of the less preferred tokens (e.g., presenting more than 6 tokens C vs. 1 token A) we might induce capuchins to choose the less preferred but more numerous type of token.

Overall, these results suggest that capuchins use similar cognitive mechanisms when evaluating options in both real and symbolic contexts. Indeed, capuchins' preferences satisfied transitivity in both contexts. At the same time, tokens were not dealt with exactly as the food they stand for, since relative values were higher in the Token condition than in the Food condition. Several factors could account for this result. First, the high memory load due to recalling the association between each token and the corresponding food. However, high memory load should have led to a more “noisy” pattern of choice in the Token condition, but this did not seem to be the case, since the variability in capuchins' performance (as measured by the variance σ2) did not significantly differ between the Food and Token conditions. Alternatively, monkeys' behavior could be explained by a decreased motivation due to the delayed feedback inherent in token exchange. This hypothesis seems, however, unlikely because our subjects never refused to participate and completed all the token trials. Moreover, the same two individuals for which tokens increased most the relative values between item pairs (Sandokan and Carlotta) were the best performers in a previous study on the estimation and combination of token quantities, where temporal discounting was at stake [12]. Nonetheless, since each token exchange for the corresponding food takes a few seconds, we cannot rule out that capuchins may have discounted the offers involving a higher number of tokens [31].

Finally, the different results obtained in the Token condition compared to the Food condition could reflect a difficulty to achieve a dual representation [3]. Specifically, capuchins may find it difficult to grasp the dual nature of tokens as it is the case for young children. In humans, the understanding and use of symbolic artifacts develops slowly because simultaneously representing both the concrete object itself and its abstract relation to what it stands for is complex [5]. DeLoache and colleagues have extensively investigated how young children use scale models (i.e., realistic miniature models of a familiar playroom) as a source of information for solving a retrieval problem. In a typical trial, children observed an experimenter hide a miniature toy in the model and were then asked to find the larger toy in the analogous location of the playroom. Children understanding of the model-playroom relation and the ability to successfully find the corresponding larger toy in the playroom developed between 2.5 and 3.0 years of age [3]–[5]. In chimpanzees tested in a similar version of this task, only a few individuals could inhibit perseverative object-oriented responses and successfully retrieved the hidden item [11].

Young children seem to fail in the scale model task because they are attentive to the real object rather than to what it stands for. When the salience of the model is decreased (for example substituting the scale model with a video clip), or when there is no need for dual representation (children are told that a “shrinking machine” transformed the playroom into the miniature model), performance improves. In contrast, performance declines when the physical salience of the scale model is increased by allowing children to play with the model before performing the task [3], [5]. A similar phenomenon might explain our results. In the Token condition capuchins might have focused on the quality of the preferred token disregarding the quantities of the two alternatives, thus choosing this token more often than the corresponding food in the Food condition. Future studies should assess whether preventing the physical interaction with tokens by eliminating the exchange procedure modifies capuchins' performance.

Interestingly, in humans a complete appreciation of the symbolic nature of tokens took long time to be achieved [32]. Around 8500 years B.C. the Sumerians started keeping track of trades by employing a system based on small clay tokens shaped differently depending on the good they stood for. The evolution of this token system reflected Sumerians' socioeconomic development. As their trades expanded, Sumerians needed to transport tokens in clay pots and, to readily identify the content of each pot, they engraved on their surfaces the type and number of the tokens contained. Nonetheless, Sumerians did not immediately realized how abstract this symbolic system could be and only after several millennia both number representation and writing evolved from the engraved clay pots.

Finally, the increased abstraction of the Token condition did not ameliorate capuchins' performance, as reported for chimpanzees [9]–[11] and young children [30], [33], [34] when symbolic representations substituted for real food. Again, limited mastery of the dual nature of tokens may have prevented capuchins from achieving psychological distancing [27]–[30]; however, this hypothesis requires further studies examining whether tokens enhance performance in tasks where inhibition is critical for success.

In conclusion, capuchin monkeys' behavior with tokens is not simply the product of instrumental conditioning, though tokens have not gained yet the status of human money. Our findings suggest that capuchins indeed treat tokens as symbols, despite experiencing the cognitive burdens imposed by symbolic representation. Thus, also non-apes have undertaken the path of symbol use and understanding, though they are far from achieving full symbolic competence.

Materials and Methods

Subjects and apparatus

Five captive-born capuchin monkeys (three males, two females, average 15.4 years, range 7–23) were tested. All subjects were already proficient in token exchange and had experience in cognitive and number-related tasks [12], [13]. No subject but one (Robot) had already participated in a previous study on transitivity of food preferences [24].

They lived in three groups at the Primate Center of the Institute of Cognitive Sciences and Technologies of CNR, Rome; each group was housed in indoor–outdoor compartments (total area: 65.4–139.5 m3, depending on group size) and tested in one of the two indoor compartments (12.2 m3 each, for all groups). All compartments were furnished with wooden perches, tree trunks and branches. Separation for individual testing was achieved by splitting the group into smaller units by means of sliding doors and then allowing one individual to enter the indoor compartment. This procedure was part of the daily routine. Monkeys were not food deprived for testing. The main meal took place in the afternoon when fresh fruits, vegetables and monkey chow were provided. Water was available ad libitum. This study complied with protocols approved by the Italian Health Ministry and all procedures were performed in full accordance with the European law on humane care and use of laboratory animals.

Subjects were tested individually in the indoor compartment; the apparatus was a black plastic table (65 cm×64 cm×13.5 cm) with two sliding aluminum trays (6.5×40 cm; 2.5 cm high), positioned at 32 cm distance from one another. Each tray had two holes (1.4 cm in diameter), one at each end; one served to allow the subject's pulling, whereas the other hole allowed the experimenter to block the tray by inserting a pin into it. All subjects were already familiar with the apparatus [12], [13]. The experiment proceeded in phases. In the preliminary phase, subjects were tested for their binary food preferences. Subsequently, preference transitivity was tested in choices between foods (Food condition). Then, in the training phase, subjects learned to exchange tokens for food. Finally, preference transitivity was tested in choices between tokens (Token condition).

Preliminary phase

Capuchins' preference for two pairs of foods (A:B and B:C, see below) was assessed. First, we carried out the preference test for the pair A:B, and then for the pair B:C. In each session, capuchins faced binary choices between different quantities of a pair (A:B or B:C). Before the beginning of each session, eight familiarization trials were carried out by presenting pair-wise comparisons between the two foods (one piece each). According to subjects' preferences, foods were referred to as food A (high-preferred) and food B (low-preferred). Similarly, when testing the other food pair, foods were referred to as food B (high-preferred) and food C (low-preferred). Individual preferences varied so that labels A, B, and C referred to different foods for different subjects (Table 2).

For the A:B pair, in each trial capuchins faced a binary choice between one or two pieces of food A and one to five pieces of food B. Therefore, the following comparisons were presented: 2A:1B, 1A:1B, 1A:2B, 1A:3B, 1A:4B, and 1A:5B; each combination was presented eight times for a total of 48 trials in a pseudo-random order. The left/right arrangement of the offers was counterbalanced within each session. Each subject received one session a day for a total of five sessions. The same procedure was employed for the B:C pair.

Testing was carried out by two experimenters: experimenter 1 sat in front of the subject's indoor compartment, with the apparatus placed on the floor between the experimenter and the capuchins' compartment. Placed between the experimenters were two opaque containers, each containing pieces of one type of food. Experimenter 2 sat next to experimenter 1 and during baiting she covered the apparatus with an opaque screen to prevent the subject from seeing the process. Then, experimenter 2 lifted the opaque screen and experimenter 1 pushed the apparatus towards the wire mesh, so that the monkey could pull one of the two trays. Both experimenters refrained from looking at the apparatus so as not to provide cues to the subject. The inter-trial interval was about 10 s.

Food condition

In each session, capuchins faced choices between different quantities of three foods, labeled A, B and C in decreasing order of preference. Choices were binary and trials with the three pairs of foods (A:B, B:C and C-A) were interleaved pseudo-randomly. Before the beginning of each session, nine familiarization trials were carried out by presenting for three times all the possible pair-wise comparisons between the three foods (one piece of food of each type). Foods were referred to as food A (high-preferred), food B (medium-preferred), and food C (low-preferred).

In each trial capuchins could face a binary choice between: (1) one or two pieces of food A and one to four pieces of food B, (2) one or two pieces of food B and one to four pieces of food C, and (3) one or two pieces of food A and one to six pieces of food C. In a session, each comparison was presented four times. For each food pair, according to each individual's indifference point, the type and number of trials presented varied across sessions, from a minimum of 60 to a maximum of 64 trials per session; no subject received all the possible 72 comparisons within a session (Table 1). The left/right arrangement of the offers was counterbalanced within each session. Each subject received one session a day for a total of five sessions. All the other features of the procedure were the same as in the preliminary phase.

Token condition

The same five capuchins were presented with the Token condition after completing all the five sessions in the Food condition. We used the same subjects and apparatus as in the Food condition.

(a) Tokens.

Tokens were objects of similar dimensions, differing in shape, material and color; in particular, we used green chips, black plastic tubes, and brass hooks. These objects were familiar to the subjects but never used in previous studies. The three tokens were pseudo-randomly assigned to the three types of food across subjects (Table 2).

(b) Training.

Subjects learned to associate each type of token to one of the three foods used in the Food condition (Table 2). Therefore, token A was associated with the high-preferred food, token B with the medium-preferred food, and token C with the low-preferred food. The training procedure consisted of placing 12 tokens of the same type (i.e., associated to the same type of food) into the indoor compartment, and repeatedly saying ‘give me’ to the monkey while requesting a token, with left hand outstretched and palm up. The reward was given upon the placement of one token into the experimenter's left hand. There was a 10-s interval between one trial and the next one. Incorrect exchanges, in which tokens were thrown or incorrectly placed into the experimenter's hand, were not rewarded. Moreover, when the subject did not exchange a token within 30 s, the trial was considered incorrect and a new trial started after 10 s.

Subjects received a training session per day. Each session consisted of two blocks of 12 trials each, for a total of 24 trials. Criterion was set at 90% correct responses within two consecutive sessions. Each subject was trained to exchange one type of token (A, B, or C) at a time, and the order in which they learned to exchange the three tokens was randomly determined. When criterion was reached for all types of token, subjects received nine sessions of consolidation with tokens A, B and C alternated across days. Capuchins completed training (including the nine sessions of consolidation) in an average of 18.2±1.7 sessions. In particular, they reached criterion in an average of 2.8±0.4 sessions for token A (range: 2–4), 2.8±0.8 sessions for token B (range: 2–6), and 3.4±1.4 sessions for token C (range: 2–9). The rate of training of the present study is similar to that reported for capuchins learning to associate different type of tokens with different quantities of food [12], [13].

(c) Procedure.

In each session, capuchins faced binary choices between different quantities of three tokens (A:B, B:C, and A:C). Before the beginning of each session, nine familiarization trials were carried out by presenting for three times all the possible pair-wise comparisons between the three tokens (one token of each type). According to subjects' preferences, tokens were referred to as token A (associated to the high-preferred food), token B (associated to the medium-preferred food), and token C (associated to the low-preferred food).

In each trial capuchins could face a binary choice between: (1) one or two tokens A and one to six tokens B, (2) one to three token(s) B and one to six token(s) C, and (3) one or two token(s) A and one to six token(s) C. In each trial, after choosing an offer type capuchins were required to exchange the token(s) selected (one at a time) before the experimenter administered the next trial; each token exchange took a few seconds and was rewarded with one piece of food (Table 2). Typically, capuchins exchanged correctly, and in the very few cases in which they did not do so, the experimenter gave the token back to the subject so that s/he could exchange it again.

In a session, each comparison was presented four times. For each token pair, according to each individual's indifference point, the type and number of trials presented varied across sessions, from a minimum of 60 to a maximum of 76 trials per session in a pseudo-random order; no subject received all the possible 88 comparisons within a session (Table 1). The left/right arrangement of the offers was counterbalanced within each session. Each subject received one session a day for a total of five sessions. All the other features of the procedure were the same as in the Food condition. The study took place between February and May 2007.

Analysis of choice patterns

We analyzed choice patterns using the method employed by Padoa-Schioppa & Assad [22], [23]. We refer to “relative” values because behavioral analyses allow measuring quantities of different goods on a common value scale up to a scaling factor. Our measure of relative value rests on the assumption of linear indifference curves: if a monkey is repeatedly offered the choice between quantities qX and qY of items X and Y (offer qYY : qXX), the rate of “Y” choices only depends on the ratio qY / qX[23].

Choice patterns recorded for each pair of items X and Y are expressed as a function of log(qY / qX), where qX and qY are, respectively, the quantities of items X and Y offered to the monkey. For each item pair, we then fit the percentage of “Y” choices with a normal sigmoid, which is a normal cumulative distribution function of the form S(x) = ∫x−∞ = N (t, μ, σ) dt. We interpret the underlying Gaussian (which has mean μ and variance σ2) as a probability distribution for the log relative value, and we compute the estimated relative value of the two items n = exp(μ). The relative value corresponds to the indifference point, i.e. the ratio of quantities for which the monkey would choose either item equally often. We indicate with V(X) the value of X, and with nX:Y the relative value of items X and Y, such that V(X) = nX:Y V(Y). For each session, we thus obtain the three probability distributions for the log relative values u = log(nA:B), v = log(nB:C) and w = log(nA:C). Under the assumption of linear indifference curves, indifference transitivity is satisfied if the following relationship holds statistically true: nA:B * nB:C = nA:C. We refer to this condition as “value transitivity.” Testing whether values satisfy transitivity reduces to testing whether the identity u+v = w holds statistically true. Because u, v and w are all normally distributed variables, transitivity violations can be identified with a z-test [23].

Supporting Information

Video S1.

Food condition. Carlotta, a female capuchin, has a choice between one cheerios (food A, on the left) and three pieces of parmesan cheese (food B, on the right). She selects the three pieces of parmesan cheese by pulling the corresponding tray.

https://doi.org/10.1371/journal.pone.0002414.s001

(4.79 MB MPG)

Video S3.

Food condition. Carlotta has a choice between three sunflower seeds (food C, on the left) and one piece of parmesan cheese (food B, on the right). She selects the three sunflower seeds by pulling the corresponding tray.

https://doi.org/10.1371/journal.pone.0002414.s003

(4.56 MB MPG)

Video S5.

Token condition. Carlotta has a choice between one green poker chip (token A, corresponding to one cheerios, on the left) and three brass hooks (token C, corresponding to one sunflower seed each, on the right). She selects the token A by pulling the corresponding tray.

https://doi.org/10.1371/journal.pone.0002414.s005

(5.28 MB MPG)

Video S6.

Token condition. Carlotta has a choice between three black plastic tubes (token B, corresponding to one piece of parmesan cheese each, on the left) and one green poker chip (token A, corresponding to one cheerios, on the right). She selects the three tokens B by pulling the corresponding tray.

https://doi.org/10.1371/journal.pone.0002414.s006

(9.35 MB MPG)

Video S7.

Token condition. Carlotta has a choice between one black plastic tube (token B, corresponding to one piece of parmesan cheese, on the left) and three brass hooks (token C, corresponding to one sunflower seed each, on the right). She selects the single token B by pulling the corresponding tray.

https://doi.org/10.1371/journal.pone.0002414.s007

(6.34 MB MPG)

Video S8.

Token condition. Carlotta has a choice between one black plastic tube (token B, corresponding to one piece of parmesan cheese, on the left) and four brass hooks (token C, corresponding to one sunflower seed each, on the right). She selects the four tokens C by pulling the corresponding tray.

https://doi.org/10.1371/journal.pone.0002414.s008

(10.39 MB MPG)

Video S9.

Token condition. Carlotta has a choice between one green poker chip (token A, corresponding to one cheerios, on the left) and five brass hooks (token C, corresponding to one sunflower seed each, on the right). She selects the single token A by pulling the corresponding tray.

https://doi.org/10.1371/journal.pone.0002414.s009

(5.53 MB MPG)

Video S10.

Token condition. Carlotta has a choice between six brass hooks (token C, corresponding to one sunflower seed each, on the left) and one green poker chip (token A, corresponding to one cheerios, on the right). She selects the six tokens C by pulling the corresponding tray.

https://doi.org/10.1371/journal.pone.0002414.s010

(12.60 MB MPG)

Acknowledgments

We thank Dan Ariely for inspiring discussions and constructive comments. We especially thank Valentina Truppa and Francesco Natale for statistical advice and Tommaso Stegagno and Luigi Baciadonna for their assistance to make the video clips. We further thank the Fondazione Bioparco for hosting our Primate Centre, our keepers Massimiliano Bianchi and Simone Catarinacci, and our technician Luigi Fidanza.

Author Contributions

Conceived and designed the experiments: EV EA AM LC. Performed the experiments: EA AM LC. Analyzed the data: EA AM LC CP. Wrote the paper: EV EA AM LC CP.

References

  1. 1. Deacon T (1997) The symbolic species: The co-evolution of language and the brain. New York & London: W. W. Norton & Co.. T. Deacon1997The symbolic species: The co-evolution of language and the brain.New York & LondonW. W. Norton & Co.527
  2. 2. Fisher SE, Marcus GF (2006) The eloquent ape: genes brains and the evolution of language. Nature Rev Genet 7: 9–20.SE FisherGF Marcus2006The eloquent ape: genes brains and the evolution of language.Nature Rev Genet7920
  3. 3. DeLoache JS (2002a) The symbol-mindedness of young children. In: Hartup WW, Weinberg RA, editors. Child psychology in retrospect and prospect: The Minnesota symposia on child psychology. Mahwah: LEA Publishing. pp. 73–101.JS DeLoache2002aThe symbol-mindedness of young children.WW HartupRA WeinbergChild psychology in retrospect and prospect: The Minnesota symposia on child psychologyMahwahLEA Publishing73101
  4. 4. DeLoache JS (2002b) Early development of the understanding and use of symbolic artifacts. In: Goswami U, editor. Blackwell handbook of childhood cognitive development. Oxford: Blackwell. pp. 206–226.JS DeLoache2002bEarly development of the understanding and use of symbolic artifacts.U. GoswamiBlackwell handbook of childhood cognitive developmentOxfordBlackwell206226
  5. 5. DeLoache JS (2004) Becoming symbol-minded. Trends Cogn Sci 8: 66–70.JS DeLoache2004Becoming symbol-minded.Trends Cogn Sci86670
  6. 6. Savage-Rumbaugh ES, Rumbaugh DM, Boysen S (1978) Symbolic communication between two chimpanzees (Pan troglodytes). Science 201: 641–644.ES Savage-RumbaughDM RumbaughS. Boysen1978Symbolic communication between two chimpanzees (Pan troglodytes).Science201641644
  7. 7. Savage-Rumbaugh ES (1986) Ape language: from conditioned response to symbol. New York: Columbia University Press. ES Savage-Rumbaugh1986Ape language: from conditioned response to symbol.New YorkColumbia University Press433
  8. 8. Savage-Rumbaugh ES, Rumbaugh DM, Smith ST, Lawson J (1980) Reference: The linguistic essential. Science 210: 922–925.ES Savage-RumbaughDM RumbaughST SmithJ. Lawson1980Reference: The linguistic essential.Science210922925
  9. 9. Boysen ST, Berntson GG (1995) Responses to quantity: Perceptual versus cognitive mechanisms in chimpanzees (Pan troglodytes). J Exp Psychol Anim Behav Process A 21: 82–86.ST BoysenGG Berntson1995Responses to quantity: Perceptual versus cognitive mechanisms in chimpanzees (Pan troglodytes).J Exp Psychol Anim Behav Process A218286
  10. 10. Boysen ST, Berntson GG, Hannan MB, Cacioppo JT (1995) Quantity-based interference and symbolic representation in chimpanzees (Pan troglodytes). J Exp Psychol Anim Behav Process 22: 76–86.ST BoysenGG BerntsonMB HannanJT Cacioppo1995Quantity-based interference and symbolic representation in chimpanzees (Pan troglodytes).J Exp Psychol Anim Behav Process227686
  11. 11. Boysen ST (2006) The impact of symbolic representations on chimpanzee cognition. In: Hurley S, Nudds M, editors. Rational Animals? New York: Oxford University Press. pp. 489–511.ST Boysen2006The impact of symbolic representations on chimpanzee cognition.S. HurleyM. NuddsRational Animals?New YorkOxford University Press489511
  12. 12. Addessi E, Crescimbene L, Visalberghi E (2007) Do capuchin monkeys (Cebus apella) use tokens as symbols? Proc R Soc Lond [Biol] 274: 2579–2585.E. AddessiL. CrescimbeneE. Visalberghi2007Do capuchin monkeys (Cebus apella) use tokens as symbols?Proc R Soc Lond [Biol]27425792585
  13. 13. Addessi E, Crescimbene L, Visalberghi E (2008) Food and token quantity discrimination in capuchin monkeys (Cebus apella). Anim Cogn 11: 275–282.E. AddessiL. CrescimbeneE. Visalberghi2008Food and token quantity discrimination in capuchin monkeys (Cebus apella).Anim Cogn11275282
  14. 14. Brosnan SF, de Waal FBM (2004) A concept of value during experimental exchange in brown capuchin monkeys, Cebus apella. Folia Primatol 75: 317–330.SF BrosnanFBM de Waal2004A concept of value during experimental exchange in brown capuchin monkeys, Cebus apella.Folia Primatol75317330

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