Perceptual control theory: Difference between revisions

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Botvinik in 2008<ref name="Botvinik 2008"/> found that all existing models of hierarchically structured behavior share at least one general assumption – that the hierarchical, part–whole organization of human action is mirrored in the internal or neural representations underlying it. Specifically, the assumption is that there exist representations not only of low-level motor behaviors, but also separable representations of higher-level behavioral units. The latest crop of models provides new insights, but also poses new or refined questions for empirical research, including how abstract action representations emerge through learning, how they interact with different modes of action control, and how they sort out within the prefrontal cortex (PFC).

Perceptual control theory (PCT) can provide an explanatory model of neural organisation that deals with the current issues. PCT describes the hierarchical character of behavior as being determined by control of hierarchically organized perception. Control systems in the body and in the internal environment of billions of interconnected neurons within the brain are responsible for keeping perceptual signals within survivable limits in the unpredictably variable environment from which those perceptions are derived. PCT does not propose that there is an internal model within which the brain simulates behavior before issuing commands to execute that behavior. Instead, one of its characteristic features is the principled lack of cerebral organisation of behavior. Rather, behavior is the organism's variable means to reduce the discrepancy between perceptions and reference values which are based on various external and internal inputs.<ref>{{cite book | last=Cools | first=A. R. | chapter=Brain and Behavior: Hierarchy of Feedback Systems and Control of Input | editor-last=Bateson | editor-first=P. P. G. | editor-last2=Klopfer | editor-first2=Peter H. | title=Perspectives in Ethology | publisher=Springer US | publication-place=Boston, MA | year=1985 | isbn=978-1-4757-0234-7 | doi=10.1007/978-1-4757-0232-3_5 | pp=109–168}}</ref> Behavior must constantly adapt and change for an organism to maintain its perceptual goals. In this way, PCT can provide an explanation of abstract learning through spontaneous reorganisation of the hierarchy. PCT proposes that conflict occurs between disparate reference values for a given perception rather than between different responses,<ref name=Mansell2011/>, and that learning is implemented as trial-and-error changes of the properties of control systems,<ref name=levels/> rather than any specific response being ''reinforced''. In this way, behavior remains adaptive to the environment as it unfolds, rather than relying on learned action patterns that may not fit.

Hierarchies of perceptual control have been simulated in computer models and have been shown to provide a close match to behavioral data. For example, Marken<ref name=Marken86>{{cite journal | last =Marken | first =Richard S. | title =Perceptual organization of behavior: A hierarchical control model of coordinated action. | journal =Journal of Experimental Psychology: Human Perception and Performance | volume =12 | issue =3 | pages =267–276 | date =Aug 1986 | doi =10.1037/0096-1523.12.3.267 | pmid =2943855 }}</ref> conducted an experiment comparing the behavior of a perceptual control hierarchy computer model with that of six healthy volunteers in three experiments. The participants were required to keep the distance between a left line and a centre line equal to that of the centre line and a right line. They were also instructed to keep both distances equal to 2&nbsp;cm. They had 2 paddles in their hands, one controlling the left line and one controlling the middle line. To do this, they had to resist random disturbances applied to the positions of the lines. As the participants achieved control, they managed to nullify the expected effect of the disturbances by moving their paddles. The correlation between the behavior of subjects and the model in all the experiments approached 0.99. It is proposed that the organization of models of hierarchical control systems such as this informs us about the organization of the human subjects whose behavior it so closely reproduces.