Do Chimpanzees ave Expectations About Reward Presentation Following Correct Performance on Computerized Cognitive Testing?

To investigate whether 2 chimpanzees had expectations regarding the outcome of their responses on a computerized task, food reward that typically was given for correct responses was withheld on some correctly completed trials. There were two types of these probe trials: those which the chimpanzees performed correctly on their own, and those during which the chimpanzees needed the experimenter\u27s assistance to complete the trial correctly. For both chimpanzees, reward procurement behaviors directed toward the experimenter occurred significantly more often on correctly completed probe trials than on incorrectly completed trials. This indicated increased expectation of food reward on correct trials as compared to incorrect trials. For 1 of the 2 chimpanzees, reward procurement behaviors were significantly more likely to occur on probe trials on which the chimpanzee received no assistance from the experimenter than on trials in which the experimenter assisted the chimpanzee. This behavioral difference was not predicated on reinforcement history, as all correctly completed nonprobe trials were rewarded whether or not assistance was provided by the experimenter. These data indicate that this chimpanzee may have a rudimentary sense of equity regarding what outcome should accompany the successful completion of trials that is dependent on the level of assistance provided by an experimenter during the trial

The Evolutionary and Developmental Foundations of Mathematics

Recent behavioral and neuroimaging studies with humans and monkeys provide compelling evidence of shared numerical capacities across species. Our understanding of the emergence of human mathematical competence is well-served by these kinds of comparative assessments

Animal Memory: Rats Bind Event Details into Episodic Memories

SummaryA recent study shows that rats remember multiple details of an event in a way that suggests those details are bound into episodic memories that the rats use when faced with a foraging task

Number Without Language: Comparative Psychology and the Evolution of Numerical Cognition

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High fidelity sorting of remarkably similar components via metal-mediated assembly.

Subtle differences in ligand coordination angle and rigidity lead to high fidelity sorting between individual components displaying identical coordination motifs upon metal-mediated self-assembly. Narcissistic self-sorting can be achieved between highly similar ligands that vary minimally in rigidity and internal coordination angle upon combination with Fe(ii) ions and 2-formylpyridine. Selective, sequential cage formation can be precisely controlled in a single flask from a mix of three different core ligands (and 33 total components) differing only in the hybridization of one group that is uninvolved in the metal coordination process

Trading Behavior Between Conspecifics in Chimpanzees, Pan Troglodytes

Bartering of commodities between individuals is a hallmark of human behavior that is not commonly seen in other species. This is difficult to explain because barter is mutually beneficial, and appears to be within the cognitive capabilities of many species. It may be that other species do not recognize the gains of trade, or that they do not experience conditions (e.g., low risk) in which barter is most beneficial. To answer these questions, we instituted a systematic study of chimpanzees’ ability to barter with each other when doing so materially benefits them. Using tokens derived from symbols they have used since infancy, pairs of adult chimpanzees could trade between themselves to obtain tokens needed to get foods. Subjects flexibly used the tokens to obtain foods from an experimenter; however, they did not spontaneously trade with their partner. After extensive training, subjects engaged in accurate trade behavior as long as an experimenter enforced the structure of the interaction; however, trade between partners disappeared when this enforcement was removed. We discuss possible reasons for these findings as well as implications for the evolution of barter across the primate lineage

Old World Monkeys are More Similar to Humans Than New World Monkeys When Playing a Coordination Game

There is much debate about how humans’ decision-making compares to that of other primates. One way to explore this is to compare species’ performance using identical methodologies in games with strategic interactions. We presented a computerized Assurance Game, which was either functionally simultaneous or sequential, to investigate how humans, rhesus monkeys, and capuchin monkeys utilized information in decision-making. All species coordinated via sequential play on the payoff-dominant Nash equilibrium, indicating that information about the partner’s choice improved decisions. Furthermore, some humans and rhesus monkeys found the payoff-dominant Nash equilibrium in the simultaneous game, even when it was the first condition presented. Thus, Old World primates solved the task without any external cues to their partner’s choice. Finally, when not explicitly prohibited, humans spontaneously used language to coordinate on the payoff-dominant Nash equilibrium, indicating an alternate mechanism for converting a simultaneous move game into a sequential move game. This phylogenetic distribution implies that no single mechanism drives coordination decisions across the primates, while humans’ ability to spontaneously use language to change the structure of the game emphasizes that multiple mechanisms may be used even within the same species. These results provide insight into the evolution of decision-making strategies across the primates

The Relationship between Event-Based Prospective Memory and Ongoing Task Performance in Chimpanzees (Pan troglodytes)

Prospective memory is remembering to do something at a future time. A growing body of research supports that prospective memory may exist in nonhuman animals, but the methods used to test nonhuman prospective memory differ from those used with humans. The current work tests prospective memory in chimpanzees using a method that closely approximates a typical human paradigm. In these experiments, the prospective memory cue was embedded within an ongoing task. Tokens representing food items could be used in one of two ways: in a matching task with pictures of items (the ongoing task) or to request a food item hidden in a different location at the beginning of the trial. Chimpanzees had to disengage from the ongoing task in order to use the appropriate token to obtain a higher preference food item. In Experiment 1, chimpanzees effectively matched tokens to pictures, when appropriate, and disengaged from the ongoing task when the token matched the hidden item. In Experiment 2, performance did not differ when the target item was either hidden or visible. This suggested no effect of cognitive load on either the prospective memory task or the ongoing task, but performance was near ceiling, which may have contributed to this outcome. In Experiment 3, we created a more challenging version of the task. More errors on the matching task occurred before the prospective memory had been carried out, and this difference seemed to be limited to the hidden condition. This finding parallels results from human studies and suggests that working memory load and prospective memory may have a similar relationship in nonhuman primates