Do Capuchin Monkeys (Cebus apella) Diagnose Causal Relations in the Absence of a Direct Reward?

Abstract

We adapted a method from developmental psychology [1] to explore whether capuchin monkeys (Cebus apella) would place objects on a “blicket detector” machine to diagnose causal relations in the absence of a direct reward. Across five experiments, monkeys could place different objects on the machine and obtain evidence about the objects’ causal properties based on whether each object “activated” the machine. In Experiments 1–3, monkeys received both audiovisual cues and a food reward whenever the machine activated. In these experiments, monkeys spontaneously placed objects on the machine and succeeded at discriminating various patterns of statistical evidence. In Experiments 4 and 5, we modified the procedure so that in the learning trials, monkeys received the audiovisual cues when the machine activated, but did not receive a food reward. In these experiments, monkeys failed to test novel objects in the absence of an immediate food reward, even when doing so could provide critical information about how to obtain a reward in future test trials in which the food reward delivery device was reattached. The present studies suggest that the gap between human and animal causal cognition may be in part a gap of motivation. Specifically, we propose that monkey causal learning is motivated by the desire to obtain a direct reward, and that unlike humans, monkeys do not engage in learning for learning’s sake.

Causal and inferential reasoning in animals.

“…Only unconfounded interventions (i.e., each object is placed on top of the detector by itself) allow for disentangling the effects of each candidate cause. In a first adaptation of this paradigm for nonhuman primates, capuchin monkeys seemed to differentiate between confounded and unconfounded interventions, at least after significant exposure to the task contingencies (Edwards et al, 2014). The extent of training, however, is key for the interpretation of these results.…”

Little Bayesians or little Einsteins? Probability and explanatory virtue in children's inferences

“…Given that non-human primates, and even rats, appear to be capable of some forms of causal reasoning (e.g. in a blicket detector task, Edwards, Rottman, Shankar, Betzler, Chituc et al, 2014; see also Blaisdell, Sawa, Leising & Waldmann, 2006), virtue-based explanatory inference may also be phylogenetically ancient.…”

Long-tailed macaques extract statistical information from repeated types of events to make rational decisions under uncertainty

“…Apes and capuchin monkeys were also tested in paradigms in which they had to make predictions based on statistical information sampled from repeated events 22,25 . Findings suggest that they relied on the frequencies at which two different objects activated a mechanical device together or separately, to predict which object was more likely to activate a device on its own.…”