Rhesus monkeys show greater habituation to repeated computer-generated images than do orangutans.

Humans and several other species of animals have demonstrated the ability to use familiarity to recognize that they have seen images before. In prior experiments, orangutans failed to show use of familiarity in memory tasks, even when other solutions were not available. We tested for evidence of habituation, a decreased response to repeated stimuli, as a behavioral indicator that repeated images were familiar to subjects. Monkeys and orangutans selected the smallest target out of four while computerized images were presented as distractors. Latency to complete the target-finding task was compared between conditions in which the distractor image was a familiar, repeating image, a novel, never-before-seen image, or no distractor was present. Rhesus macaques showed significant habituation, and significantly more habituation than orangutans, in each of four experiments. Orangutans showed statistically reliable habituation in only one of the four experiments. These results are consistent with previous research in which orangutans failed to demonstrate familiarity. Because we expect that familiarity and habituation are evolutionarily ancient memory processes, we struggle to explain these surprising, but consistent findings. Future research is needed to determine why orangutans respond to computerized images in this peculiar way.

Animal Emotions and Consciousness: Researchers' Perceptions, Biases, and Prospects for Future Progress.

Do animals have emotions? Scientists and philosophers have long struggled with this question, with debates ranging from whether animals experience an "internal world" to whether we are capable of studying it. Recently, theoretical, and methodological advances have rekindled this debate, yet, it is unclear where the scientific consensus on these topics lies today. To address this gap, we administered a survey of professional animal behavior researchers to assess perceptions regarding (1) the taxonomic distribution of emotions and consciousness in non-human animals, (2) respondents' confidence in this assessment, and (3) attitudes towards potential for progress and possible pitfalls when addressing these questions. In general, animal behavior researchers (n=100) ascribed emotionality and consciousness to a broad swath of the animal taxa, including non-human primates, other mammals, birds, and cephalopods, with varying degrees of confidence. There was a strong positive relationship between how likely a respondent was to attribute emotions to a given taxa and their confidence in that assessment, with respondents assuming an absence of emotions and consciousness when they were unsure. In addition, respondents' assessments were shaped by several traits (e.g., advanced cognitive abilities, consciousness) that they also admitted were not necessary for an animal to experience emotions. Ultimately, a large majority of researchers were optimistic that tools either currently exist or will exist in the future to rigorously address these questions (>85%) and that animal behavior, as a field, should do more to encourage emotions research (71%). We discuss implications of our findings for publication bias, ethical considerations, and identify an emergent consensus for the need of a functional definition of emotions to facilitate future work.

The effects of positive and negative experiences on subsequent behavior and cognitive performance in capuchin monkeys (Sapajus [Cebus] apella).

Our understanding of animals' affective processing is notably limited compared to the wealth of research on humans, largely due to difficulties in measurement. Moreover, despite a recent increase in the understanding of the interaction between affect and cognition in animals, most research has focused on negative affect, with the result that we continue to know little about the effects of positive affect. In this study, we tested 15 adult capuchin monkeys (Sapajus [Cebus] apella) using a novel methodology that took advantage of capuchins' species-typical behavior to engineer both a positive and negative experience, using the same apparatus to minimize extraneous impacts. Following a positive or negative experience (that presumably induced positive and negative affect, respectively), or a control with no manipulation, we assessed subjects' performance on a cognitive task, a computerized delayed match-to-sample. As predicted, behavior following the negative condition suggested a negative affective state, with increased rates of scratching (commonly used as an indicator of stress in nonhuman primates) compared to both the positive and control conditions. Cognitive performance was also impaired in the negative condition compared to the other two. Contrary to predictions, however, the positive condition did not have a facilitative effect on cognitive performance, but behavioral results indicate that we may not have induced a truly positive affective state. Although we add to evidence that a negative experience can influence subsequent behavior and cognitive performance in nonhuman primates, our work highlights our lack of knowledge about the impact of positive affect, if any, on behavior and cognition. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Post-event misinformation effects in a language-trained chimpanzee (Pan troglodytes).

Errors of source monitoring are widespread human memory challenges, and our memories are subject to distortion upon the presentation of subsequent misinformation. Less is known about if and when misinformation effects occur in nonhuman species' memory. Here we tested a symbol-trained chimpanzee's recall memory of a hidden food item's identity after a 10-min delay. During this delay, the subject was sometimes (depending on the condition) shown consistent or inconsistent video information about the identity of the food, before being asked to name the item to a second experimenter blind to the reward and condition. Across all conditions, our subject, Sherman, correctly named the food item at above chance levels. In the Inconsistent condition, in which Sherman was shown a video with misleading information, his performance was the worst of all conditions (although accuracy was still high). Interestingly, however, during three of the four trials in this condition in which Sherman made a mistake, he incorrectly named the food item shown during the misleading video information. These results provide evidence that chimpanzees, like humans, may be vulnerable to misinformation effects, even when that misleading information is presented in a different modality (video) than the original live event memory, demonstrating further commonality between human and ape memory systems.