Edited by: Axel Cleeremans, Université Libre de Bruxelles, Belgium
Reviewed by: Shimon Edelman, Cornell University, USA
*Correspondence:
This article was submitted to Frontiers in Theoretical and Philosophical Psychology, a specialty of Frontiers in Psychology.
This is an open-access article distributed under the terms of the
Clark's synthesis of much recent work on sensory and motor systems in the brain is at once radical and curiously traditional. It is radical, among other things, concerning what representations are, how they are constructed, and what sensory and motor representations have in common. But it is traditionally cognitivist in viewing the main task of brains as being that of representing the world.
What this traditional orientation tends to neglect is the role of the brain as a system for selecting among available actions. This phenomenon has an ultimate aspect regarding the external standards relevant to assessing actions. Various behavioral ecological schemes for ranking actions in terms of their contribution to quantities such as fitness, and economic models of revealed preference, are the leading theoretical players here. The phenomenon also has a proximal aspect, which concerns the specific biological mechanisms, including neural ones, by means of which the values of different available actions might be represented, and selections between them made. On this topic the recent explosion of neuroeconomic research on decision processes in the brain is urgently relevant.
Natural agents have limited means of action, and those means have alternative – sometimes mutually exclusive – uses. That is to say the
Neither the ultimate nor the proximal aspects of the problem of selecting between behaviors play a significant role in Clark's account. Natural selection, fitness, and biological descendents are not mentioned at all, and cognate concepts like adaptiveness feature in diluted form. There's similarly little mention of decision and choice as theoretically understood in economics including neuroeconomics, none of incentives, and reward and utility appear only in the course of musing over whether it is possible that cognitive neuroscience could do without reference to either (section 5.1). Clark does make some important points about action-centric
Of course, no survey can cover anything that anyone thinks is relevant, and it's very easy to complain about things that are left out. Clark's lack of engagement with neuroeconomics means missing a specific opportunity to make his general case even more compelling, because what is emerging in that field complements his case about sensory and motor systems in deep ways.
In his section (3.2) Clark apparently takes seriously the concern that an agent with the sort of brain that he's been describing would be expected to “seek a nice dark room and stay in it”. Clark disposes of the worry by pointing out that creatures with real biological needs should “expect” to follow exploratory strategies, and that these expectations themselves should recruit both perception and action. This is part of a reasonable and interesting response, but action selection under those conditions (as with most others) would still require some way of dealing with specific questions, such as where and how to forage, and how to trade off foraging with other expected behaviors such as predator avoidance and reproduction.
A related move appears later, in section (5.1) when he considers an austere vision of cognition that does without reference to goals and rewards, in favor of comprehensive analysis in terms of expectations. Clark correctly holds back from endorsing this possibility, but for relatively generic reasons to the effect that even if some description is in principle replaceable, it may be convenient to continue using it. This misses the main chance. Recent work on the neural implementation of decision in various vertebrates including humans has produced a body of results highly congenial to the unifying vision Clark supports.
Consider saccadic movements in rhesus monkeys. A key component in the neural implementation of these movements is the lateral intraparietal area (LIP), which comprises a topographic map integrating locations in the visual field and aspects of the muscular plans that would effect the centering of gaze on those locations. It, along with a network of other maps with varying topographies in the frontal eye fields, superior colliculus and related areas, provides a striking illustration of what Clark calls an “action-centric” representation. In addition, as studies including Platt and Glimcher (
There's more. The expected relative reward values attached to saccadic and other movements are not