Are Affordances Plausible? Updating Some Intuitions

In the previous post, I laid out the basic distinction between direct and indirect theories of perception. The basic issue is how to get to behaviourally relevant properties. Such properties of the world have to be partly about the organism, and not just the world; not just 'mass', which is something about the world, but 'moveability' which is something about the world, relative to the organism. If there are properties like these out in the world, and we can perceive them, then perception can, in principle, be direct. If there aren't properties like these there to be perceived, we would have to invent them, and perception would have to be indirect. The ecological hypothesis has to begin by finding behaviourally relevant properties out in the world, ready to be perceived without having to be invented; we need to find affordances. 

The problem is that this seems to be madness, right off the bat. It seems bizarre to think that things separate from the organism could possibly have properties that have anything to do with the organism. Why would they have such things? Surely things can only have properties that are about themselves and make them what they are? 

This post will talk about some pieces of information that make this at least plausible; the next post will talk about the specific ecological hypothesis about affordances that tries to implement that plausibility. To get to that plausibility, I am going to have to update your intuitions about what is simple, and what sorts of things can be physically real, and along the way introduce some useful vocabulary I will do everything I can to use clearly. 

Brains Don't Have to be Computers (A Purple Peril)

A common response to the claim that we are not information processors is that this simply cannot be true, because it is self-evidently the case that brains are transforming and processing information - they are performing computations. Greg Hickok throws this ball a lot, and his idea is clear in this quote from his book 'The Myth of Mirror Neurons':

Once you start looking inside the brain you can’t escape the fact that it processes information. You don’t even have to look beyond a single neuron. A neuron receives input signals from thousands of other neurons, some excitatory, some inhibitory, some more vigorous than others. The output of the neuron is not a copy of its inputs. Instead its output reflects a weighted integration of its inputs. It is performing a transformation of the neural signals it receives. Neurons compute. This is information processing and it is happening in every single neuron and in every neural process whether sensory, motor, or “cognitive.”

Hickok, pg 256.

There are two claims here. First, neurons are processing information because their input is not the same as their output; they are transforming the former into the latter. Second, this process is computational; 'neurons compute'.

This is a widely held view; psychologist Gary Marcus even wrote about this in the NYT saying 'Face it, your brain is a computer'. In response, Vaughn Bell at Mindhacks posted about this op-ed and this issue in a nicely balanced piece called 'Computation is a lens'. He sums up the issue nicely by asking 'Is the brain a computer or is computation just a convenient way of describing its function?'. The answer, I propose here, is that computation is a fantastically powerful description of the activity of the brain that may or may not be (and probably isn't) the actual mechanism by which the brain does whatever it does. This is ok, because, contra Hickok,  not every process that sits in between an input and a different output has to be a computational, information processing one.