Lecture 21: Barriers to Ecological Realism (Turvey, 2019, Lectures on Perception)

Last Lecture Turvey introduced the notion of ecological realism; realism that has a species-dependence to it. Normally a realism is for everyone, but different organisms inhabit different habitats and/or niches, and have different job descriptions. So another preliminary that needs to be dealt with is that there are immediate and long-standing objections to ecological realism that need to be noted and addressed. The two main ones addressed in this Lecture are dualism and the doctrine of physics as complete.

Dualism is relatively easily addressed, and replaced with the notion of organism-environment systems as the unit of analysis. We have covered this already in Lectures 2 and 3. Here, Turvey talks about earthworms to make the point. 

Earthworms are not, in and of themselves, well suited to life on land; specifically, they are bad at balancing the amount of water in them. But they live and thrive in soil, so they must have some adaptations to rely on. But these adaptations are not solely in the earthworm; instead, the earthworm-soil system work as a unit to provide the functionality of a kidney. The properties of soil that support this are used and also altered by the earthworm's activity, as it burrows and tunnels through the soil. The adaptations for becoming a land-dwelling animal are distributed throughout a system. There simply is no dualism. (Recall also that the last Lecture was about getting 'mind' things like agency out of thermodynamics, so that it as all made of the same sort of stuff.)

Dualism then entails a variety of doctrines, many of which we have encountered throughout the Lectures (e.g. the doctrine that reality is predicative). These are all problematic, and will need to be replaced (that work is coming up shortly). Turvey spends time in this Lecture on the doctrine that physics is complete, and points to some obvious problems. 

First, this doctrine isn't claiming that the current state of the science of physics is complete; that's obviously not true. The doctrine is about taking the current state as the basis for all discussion of how perception might work. We've seen this prominently in the discussion of sensations as the necessary raw material for perception, because that is what current physics has to offer. The fact this leads to problems is for psychology to solve, not cause for changes to physics. But it's actually a hint that physics has work to do for us! 

Turvey describes this with the example of reflected light; the textbook physics analysis is for light being scattered only once by a surface, when in reality surfaces have texture and light is scattered in multiple ways. This fact becomes a problem a perceptual system must solve, under the doctrine of physics as complete, and so theories are proposed for how cognition copes with these issues via inference, etc. But actually, this fact of reflection is a problem for physics as we currently do it to solve! The raw material for perception is what actually happens, not the simplified physical model, and Turvey reviews one experiment that shows this (Bloj et al, 1999). 

Turvey ends by pointing out that even Bayesian approaches to the necessary inference suffers from this fundamental problem; there are too many possible priors and no principled way to select which apply to what situation. Again, despite there being objections to ecological realism, the problems for the opposition remain unsolvable and there are hints that actual perceivers do not suffer these problems. The stage is nearly set for the ecological approach to be unveiled in full.