Evolutionary roots of motor planning: The end-state comfort effect in lemurs.

Abstract

Humans (Homo sapiens) anticipate the consequences of their forthcoming actions. For example, they grasp objects with uncomfortable grasps to afford comfortable end positions-the end-state comfort (ESC) effect. When did such sophisticated motor planning abilities emerge in evolution? We addressed this question by asking whether humans' most distant living primate relatives-lemurs-also exhibit the ESC effect. We presented 6 species of lemurs (Lemur catta, Eulemur mongoz, Eulemur coronatus, Eulemur collaris, Hapalemur griseus, and Varecia rubra) with a food extraction task and measured the grasp used-either a canonical thumb-up posture or a noncanonical thumb-down posture. The lemurs adopted the thumb-down posture when that hand position afforded a thumb-up posture following object transport, thereby exhibiting the ESC effect. We conclude that the planning abilities underlying the ESC effect evolved at least 65 million years ago, or 25 million years earlier than previously supposed based on an earlier demonstration of the ESC effect in cotton-top tamarins (Saguinus oedipus; Weiss, Wark, & Rosenbaum, 2007). Because neither cotton-tops nor lemurs are tool users, the data suggest that the cognitive abilities implicated by the ESC effect are not sufficient, although they may be necessary, for tool use.

The continuous end-state comfort effect: weighted integration of multiple biases

“…Adalbjornsson et al 2008;Thibaut and Toussaint 2010), with clinical populations (e.g. Hughes 1996;Steenbergen et al 2000;van Swieten et al 2010), in monkeys (Chapman et al 2010;Weiss et al 2007), and also for different continuous tasks (Cohen and Rosenbaum 2004;Schütz et al in press;Zhang and Rosenbaum 2008).…”

Comparative investigations of manual action representations: evidence that chimpanzees represent the costs of potential future actions involving tools

“…There is mounting evidence that a key function of the extended motor system is generating predictions of the sensory consequences that are likely to arise from future movements, and using that information to estimate motor costs and select actions. Investigations of the grip-selection behaviours of a variety of primates suggest that these feed-forward processes are not unique to humans, and may exist in species that are not known users of tools in nature, including lemurs [45], tamarins [44] and rhesus monkeys [47]. Our findings with chimpanzees extend these previous results by demonstrating that some non-human primates are able to cope with action-selection planning even when tools are used to interact with goal objects located distally (away from the body).…”

The development of tool manufacture in humans: what helps young children make innovative tools?

“…However, this end-state comfort effect occurs only when the tool use is self-directed rather than directed towards another object [27]. Interestingly, this end-state comfort effect has also been observed in lemurs [28] and cotton-top tamarins [29], suggesting that these rudimentary tool-use-related planning abilities either emerged at least 65 Myr ago, or they represent a convergent process in the evolution of motor systems. Furthermore, even younger infants (9 -10 months old) could use a tool to pull an out of reach toy towards themselves, but increasing the spatial gap between the tool and the toy decreased performance significantly [30].…”