Saturday, 16 September 2017

The Information for Progressive Occlusion

Gibson's ecological psychology is weird, if you are coming from a more traditional information-processing background. The two approaches make radically different assumptions about the nature of the world to be perceived; they have radically different ontologies. This means that there is little if any useful overlap in the way they do things, and communicating across the gap is very hard. I have a recent paper - preprint here - where I go into detail about the two ontologies as I defend ecological psychology from interface theory. It's essentially Turvey et al, 1981, but that's a bear of a read if you aren't already ecologically minded. Do mine first :)

Anyway, concrete examples help. My go-to is the outfielder problem but people are tired of that one. My other favourite is progressive occlusion (Gibson, Kaplan, Reynolds & Wheeler, 1969; Kaplan, 1969). Gibson worked this example up himself in great detail and so it stands as a nice concrete example to illustrate some elements of the ecological ontology. Given the recent total solar eclipse, it seems like the right time to blog it!

This post will review occlusion, talk about how it works and work with some demos. These are all linked from here; there is Matlab/Psychtoolbox code to run a demo, a video of that running and a Powerpoint with some slides. I'll refer to these throughout - occlusion is a dynamic process and so you need to see it moving for it to make sense.