Showing posts with label top down. Show all posts
Showing posts with label top down. Show all posts

Thursday, 12 January 2017

Chandaria Lectures: Andy Clark

In this post, Sophie Stammers reports from the Chandaria Lectures, hosted by the School of Advanced Study at the University of London. Professor Andy Clark, of the University of Edinburgh, gave the annual lecture, where he introduced the notion of ‘predictive processing’. Over the course of the three lectures, he put forward the case for understanding many of the core information processing strategies that underlie perception, thought and action as integrated through the predictive processing framework.

On a model of perception popular with Cartesians, and undoubtedly dominant in areas of the cannon that I was acquainted with as an undergraduate, perception is something of a passive business. Perceivers employ malleable receptor systems that (aim to) faithfully imprint the world as it is, delivering a raw stream of information that is made sense of downstream in later processing. Clark dubs this the “cognitive couch potato view”. Despite its past popularity, this view seems incompatible with evidence from multiple research streams in cognitive science which indicate that perceivers are far from passive, and bring many of their own expectations to the table. Predictive processing (PP) aims to provide a story which both accounts for and unifies these findings, whilst also doing justice to the human experience in the midst of it all.  

PP systems don’t just take in sensory information from the world, they are constantly trying to actively predict the present sensory signals with use of probabilistic models. Incoming sensory signals are met by a flow of top-down prediction, and when this matches the sensory barrage, the system has unearthed the most likely set of causes that would give rise to the particular experience. “Prediction errors” (information about mismatches between current prediction and sensory information) indicate a gap in the predictive model, and that a new hypothesis should be selected to accommodate the current sensory signal.

Maybe, rich world-revealing perceptions – as of tables, chairs, conversations, lovers, etc – only arise from the otherwise indiscriminate sensory barrage when the incoming sensory signal can be matched with top down predictions.