Equivalence classification, learning by exclusion, and long-term memory in pinnipeds: cognitive mechanisms demonstrated through research with subjects under human care and in the field

Abstract

Comparative cognition, as an interdisciplinary field, should utilize a holistic approach for studying cognitive mechanisms. We suggest that research with species of interest should employ both work with animals under human care and in the field. This complimentary approach allows for a better understanding of functional cognitive mechanisms themselves (i.e., comparative cognition regarding processes), and how these skill sets can relate to a particular species’ ecological niche. We suggest that research evidence for equivalence classification, learning by exclusion, and long-term memory in pinnipeds can provide a foundation for discussion and implementation of a two-pronged methodological approach utilizing ‘lab’ and field’ work. First, we describe evidence from research with pinnipeds under human care supporting each of these cognitive abilities, then follow this with evidence for implications of these mechanisms from complimentary field research. Lastly, we provide a brief discussion of implementation of a purposeful and two-pronged research approach as an understanding of pinnipeds’ high levels of cognitive flexibility may underlie their success for navigating the ever-changing, and often human-altered, natural environment.

Caution is required when considering sentience in animals: a response to the commentary by Briffa (2022) on “Hermit crabs, shells, and sentience” (Elwood 2022)

Abstract

My recent review examined the complex and intimate relationship between hermit crabs and the empty gastropod shells upon which they depend for survival. Because shells come with costs as well as benefits, the crabs are highly selective about which ones they prefer to occupy. Thus, a new shell is investigated and the information that is gathered appears to be compared with their existing shell before a decision is made. This is often prolonged and complex. Crabs also fight for shells and again the information that is gathered and used to inform fight decisions is complex. In my review, I consider these and other situations with reference to the possibility of sentience (including awareness). The excellent commentary from Mark Briffa expands on aspects of sentience and invokes the use of Lloyd Morgan’s Canon to avoid suggesting complex abilities when simpler explanations would suffice. I agree with this approach. However, I also suggest that when simpler explanations appear not to explain the data, then it is reasonable to consider if more complex mental abilities might be used. I also like Briffa’s suggestion that the use of an apparently higher mental faculty might result in a mechanism that is simpler than a large number of apparently simple decisions used to make complex decisions.

Serial visual reversal learning in harbor seals (Phoca vitulina)

Abstract

Progressively improving performance in a serial reversal learning (SRL) test has been associated with higher cognitive abilities and has served as a measure for cognitive/behavioral flexibility. Although the cognitive and sensory abilities of marine mammals have been subject of extensive investigation, and numerous vertebrate and invertebrate species were tested, SRL studies in aquatic mammals are sparse. Particularly in pinnipeds, a high degree of behavioral flexibility seems probable as they face a highly variable environment in air and underwater. Thus, we tested four harbor seals in a visual two-alternative forced-choice discrimination task and its subsequent reversals. We found significant individual differences in performance. One individual was able to solve 37 reversals showing progressive improvement of performance with a minimum of 6 errors in reversal 33. Two seals mastered two reversals, while one animal had difficulties in learning the discrimination task and failed to complete a single reversal. In conclusion, harbor seals can master an SRL experiment; however, the performance is inferior to results obtained in other vertebrates in comparable tasks. Future experiments will need to assess whether factors such as the modality addressed in the experiment have an influence on reversal learning performance or whether indeed, during evolution, behavioral flexibility has not specifically been favored in harbor seals.

Count-based decision-making in mice: numerosity vs. stimulus control

Abstract

Numerical and temporal control of behavior is ubiquitous across many species of animals. Recent studies showed that in the presence of reliable discriminative stimuli, mice ignore temporal relations and probabilistic information but when discriminative stimuli become non-informative, the same mice can spontaneously start relying on previously experienced time intervals and probabilities. Similar dynamics do not readily generalize to counting behavior since the response-outcome contingency functions differ when reinforcement depends on the number vs. timing of responding. In the current study, mice (N = 32) learned to press two different levers 10 (few) or 20 (many) times, while the active lever was signaled by a light stimulus. The probability of the few/many trials was manipulated between groups. During testing, the informative value of light stimulus was eliminated by signaling both few- and many-levers. In a quarter of training trials, mice ignored the discriminative stimulus and adopted a numerical decision strategy (starting to respond on the few-option and then switching to the many-option in many trials) that was sensitive to probabilistic information. The frequency but not the probability-sensitive parametrization of switching behavior changed when the discriminative stimulus became non-informative in testing. These findings suggest that there is a relatively strong representational control over counting behavior even in conditions that afford strong stimulus control.