Abstract
Gorillas (Gorilla gorilla gorilla) fail to learn abstract cues of differential outcomes in a novel cognitive bias test
Highlights
In order to assess mood state in three male western lowland gorillas housed in a bachelor group, we developed a novel version of a cognitive bias task
If the gorillas had successfully learned to discriminate between the two conditions, they would have touched the side corresponding to more food rewards faster than they selected the side associated with fewer rewards
These results show that, even though the gorillas failed to reach criterion, Kongo successfully learned the conditional discrimination to some degree, as demonstrated by his reaction times and the fact that he performed above chance on both trial types
Summary
In order to assess mood state in three male western lowland gorillas housed in a bachelor group, we developed a novel version of a cognitive bias task. Like other primates, gorillas may respond differently to quantities of edible and inedible items They may struggle with learning conditional discriminations when cues to differential responses and outcomes are arbitrary rather than intuitively connected. These studies highlight the importance of methodology when devising tests to assess cognition or affect in nonhuman primates. Most relevant to the current study, Keen et al (2014) examined the effects of enrichment on cognitive bias in grizzly bears by requiring active responding to two stimuli These researchers provided positive reinforcement for both responses; the difference being the quantity of food awarded for a correct response to each stimulus. The bears in this study did not show the expected optimism following enrichment, this method seems promising for use with other species
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