Chapter 4 - Action and Expected Experience
Presented by Zoe Jenkin
The first three chapters of The Predictive Mind sketch how prediction error minimization underlies all perceptual processing, explaining various features of the mind using one unified framework. Chapter four addresses the question of how action fits into the PEM framework, arguing not only that PEM can adequately accommodate action, but also that action plays a crucial role in minimizing prediction error. We end up with a picture on which in any given case of a prediction error (a discrepancy between the prediction of the system and the sensory input), this error can in principle be minimized in one of two ways—by revising one’s priors and generating a new hypothesis, or by acting so as to selectively sample the world in a way that makes the input data match the selected hypothesis. An example of such selective sampling might be, if the system predicts that there will be a face before it, it will fixate its eyes toward the region where the prediction dictates a nose will be, and scan for a surface with a characteristically nose-like slope. Hohwy notes that this active, selective sampling method will be more efficient than random sampling, because it will target regions of space where the hypothesis makes a particular or unique prediction and so can easily be confirmed or disconfirmed. On this view, “perceiving and acting are but two different ways of doing the same thing” (71), where that “thing” is minimizing prediction error.