Episodic-like memory in common bottlenose dolphins

Replay of incidentally encoded episodic memories in the rat

Although events are not always known to be important when they occur, people can remember details about such incidentally encoded information using episodic memory. Importantly, when information is explicitly encoded for use in an expected test of retention (as in most assessments in animals), it is possible that it is used to generate a planned action1,2,3; thus, the remembered action can occur without remembering the earlier episode. By contrast, when a test is unexpected, transforming information into an action plan is unlikely because the importance of the information and the nature of the test are not yet known. Thus, accurate performance in an unexpected test after incidental encoding documents episodic memory.1,2,3,4,5,6,7,8 Here, we present evidence that rats replay episodic memories of incidentally encoded information in an unexpected assessment of memory. In one task,9 rats reported the third-last item in an explicitly encoded list of trial-unique odors. In a second task,10 rats foraged in a radial maze in the absence of odors. On a critical test, rats foraged in the radial maze, but scented lids covered the food. Next, memory of the third-last odor was assessed. All participating rats correctly answered the unexpected question. These results suggest that rats encoded multiple pieces of putatively unimportant information, and later they replayed a stream of episodic memories when that information was needed to solve an unexpected problem. We propose that rats replay episodic memories of incidentally encoded information, which documents a critical aspect of human episodic memory in a non-human animal.

Bottlenose dolphins are sensitive to human attentional features, including eye functionality

The ability to attribute attentional states to other individuals is a highly adaptive socio-cognitive skill and thus may have evolved in many social species. However, whilst humans excel in this ability, even chimpanzees appear to not accurately understand how visual attention works, particularly in regard to the function of eyes. The complex socio-ecological background and socio-cognitive skill-set of bottlenose dolphins (Tursiops sp.), alongside the specialised training that captive dolphins typically undergo, make them an especially relevant candidate for an investigation into their sensitivity to human attentional states. Therefore, we tested 8 bottlenose dolphins on an object retrieval task. The dolphins were instructed to fetch an object by a trainer under various attentional state conditions involving the trainer's eyes and face orientation: 'not looking', 'half looking', 'eyes open', and 'eyes closed'. As the dolphins showed an increased latency to retrieve the object in conditions where the trainer's head and eyes cued a lack of attention to the dolphin, particularly when comparing 'eyes open' vs 'eyes closed' conditions, we demonstrate that dolphins can be sensitive to human attentional features, namely the functionality of eyes. This study supports growing evidence that dolphins possess highly complex cognitive abilities, particularly those in the social domain.

Social and vocal complexity in bottlenose dolphins

Bottlenose dolphins are highly social, renowned for their vocal flexibility, and possess highly enlarged brains relative to their body size. Here, we discuss some of the defining features of bottlenose dolphin social and vocal complexity and place this in the context of their cognitive evolution.

Memory: Dolphins remember incidental events

A fundamental problem in the evolution of cognition is the search for complex memory systems given the longstanding belief that complex cognition is unique to humans. Along these lines, new research suggests that bottlenose dolphins can answer unexpected questions after encoding information that was seemingly unimportant when it was encountered.