A tool to act blind? Object-assisted eye-covering as a self-handicapping behavior and social play signal in Balinese long-tailed macaques.

Self-handicapping behaviors evolved as honest signals that reliably reflect the quality of their performers. In playful activities, self-handicapping is described as intentionally and unnecessarily putting oneself into disadvantageous positions and situations. Self-handicapping during play may allow individuals to learn to cope with unexpected events by improving sensori-motor coordination, as well as function as a play solicitation signal. One such self-handicapping behavior involves moving about while deliberately covering one's eyes. We conducted a quantitative study of object-assisted eye-covering (OAEC) in a population of free-ranging Balinese macaques. After evaluating the frequency, form, distribution, and context of OAEC, we measured the responses this behavior elicited (1) in the performers with a focus on sensori-motor self-handicapping, and (2) in their conspecifics, with an emphasis on whether, and if so how, OAEC may facilitate social play. Our data provided some support for several hypotheses: OAEC is a sensori-motor self-handicapping behavior, an attention-getting cue, a social play signal, and a socially self-handicapping tactic during social play. We discuss our results from the perspective of tool-assisted self-handicapping behavior, propose a scenario to account for the emergence of this behavioral innovation, and speculate on the cultural nature of OAEC.

Decision formation in parietal cortex transcends a fixed frame of reference.

Neurons in the lateral intraparietal cortex represent the formation of a decision when it is linked to a specific action, such as an eye movement to a choice target. However, these neurons should be unable to represent a decision that transpires across actions that would disrupt this linkage. We investigated this limitation by simultaneously recording many neurons from two rhesus monkeys. Although intervening actions disrupt the representation by single neurons, the ensemble achieves continuity of the decision process by passing information from currently active neurons to neurons that will become active after the action. In this way, the representation of an evolving decision can be generalized across actions and transcends the frame of reference that specifies the neural response fields. The finding extends previous observations of receptive field remapping, thought to support the stability of perception across eye movements, to the continuity of a thought process, such as a decision.