Relational Theories of Affordances are Functional, Not Mechanistic (A Purple Peril)

Everyone and their dog has a theory about how to interpret Gibson's famously vague definition of affordances;

The affordances of the environment are what it offers the animal, what it provides or furnishes, either for good or ill....an affordance is neither an objective property nor a subjective property; or it is both if you like. An affordance cuts across the dichotomy of subjective-objective and helps us to understand its inadequacy. It is equally a fact of the environment and a fact of behavior. It is both physical and psychical, yet neither. An affordance points both ways, to the environment and to the observer.

There are two basic flavours of theories: affordances as dispositional properties of the environment (Turvey, Shaw, Reed & Mace, 1981; Turvey, 1992) and affordances as relational features of the animal-environment system. (A recent paper has just claimed they should be best understood as events, but to be honest I don't really know what's motivating this). The two most recent and popular relational accounts are Chemero's book (Chemero, 2009; see these posts on the relevant chapter) and Rietveld & Kiverstein (2014) in a paper entitled 'A Rich Landscape of Affordances'. Their goal, like most of the relational accounts, is to handle higher-order cognition by scaling up affordances to support it (our move, in contrast, has been to expand the uses of perceptual information; Golonka, 2015; Golonka & Wilson, 2016 preprint).

I am firmly in the 'affordances as dispositional properties' camp (see, for example, the discussion section of my recent throwing paper for an extended analysis). Specifically, they are dynamically defined dispositional properties of objects and events in the context of tasks. The reason is that this is the only way affordances can be the kind of thing that can create information and therefore be perceivable. They have to be 'out there' and made of things that light can bounce off, for example, and relations between organism and environments are not typically such things. In addition, if they do not exist until perceived, we need a story to explain how we come to learn to perceive them, and there is no viable ecological framework that will make this happen (Wilson et al, 2016).

Reading this material with my new mechanism glasses on has given me a new, concise way to identify the problems with these relational accounts:

Affordances-as-relations theories are all functional explanations, and not mechanistic explanations

Functional explanations are ones that take a capacity and break it down into sub-capacities in order to explain it; for example, defining an affordance as "a relation" between "a possibility for action" offered by the environment to an organism "with some set of abilities". These capacities do not point to specific real components, but describe things the system does that help constitute this other, bigger thing the system does. They are not necessarily wrong, just limited. Functional explanations have been the norm in cognitive science for as long as we've been going and many people think this is all we get. Mechanistic explanations that point to real parts and processes have many advantages but are not always possible. 

People presenting these theories want their relational affordances to do actual work in explaining behaviour, of course. But the way in which they talk reveals that if there is anything doing actual work in their accounts, it's properties of the environment. For example, Rietveld and Kiverstein defend relations this way:

We argue that the existence of affordances is not dependent on the actual engagement with an affordance of any particular individual, but affordances nevertheless have an existence that is relative to a form of life"

pg 335

This is actually a good definition of a dispositional property, except that dispositions have the additional advantage of existing prior to a particular individual coming into contact with it.

In another example,

Affordances are just aspects of a niche, so if the niche to which an affordance belongs ceases to exist so also will the affordance. Still the aspect of the material environment may well continue to offer possibilities for other forms of life in which relevant abilities are found (emphasis mine).

pg 337

This and several other examples show that it's the 'material environment' doing most of the important affordance work here.

Here's the thing to remember; Turvey's (1992; Turvey et al, 1981) dispositional analysis completely accounts for all these features. Affordances are the dispositions of the environment, but then there are effectivities, which are the complementary dispositional properties of the organism. The dispositional analysis then makes affordances and effectivities real parts that exist independently of each other, things that can be objectively defined and investigated and that therefore support the development of mechanistic models. The relational work happens when the affordance is perceived; the act of perceiving and acting on an affordance is an act of placing oneself in a relation to that affordance so that the opportunity for action it presents is taken up.

What's Limiting Affordances-as-Relations to be Only Functional?
While every camp has it's favourite Gibson quotes to back themselves up, the one constant in his contradictory and incomplete analysis of affordances is that in order for them to be interesting to a theory of behaviour, they must be perceivable. This means that must be able to create information, and this means at some point some light has to hit something and get structured by that interaction (or the equivalent for the acoustic array, etc). If affordances are properties then this can happen. If they are relations, there is as yet no story about how this occurs. Affordances-as-relations simply pick out a functional level description of an opportunity for action. This allows you to talk about things like social affordances, for example. But the cost of this is that it is as yet unclear how such relational affordances can be perceived because there is nothing identified that energy media can interact with.

So right now, affordances-as-relations accounts cannot explain how they are perceived and have their effect on behaviour. This limits them to be functional level descriptions and makes them of limited use in ecological explanations of behaviour.

Summary
Affordances-as-relations theories can only support functional explanations of behaviour, while affordances-as-dispositions accounts can support mechanistic explanations and models. In addition, relational accounts suffer from the problem that it's not clear affordance relations are real enough to support behaviour; how do these things create ecological information? All attempts to solve this problem are either unsatisfactory (Chemero simply declares it to be all good in his book) or they depend on the reality of properties in the world to work (see above). Given that we want mechanistic models, and given that constraining affordances in a way that makes them not everything but in principle perceivable then supports such models, I suggest that treating affordances as dispositional properties is an important discipline for the field to progress.

This might also account for Chemero's opposition to mechanistic modelling. His notion of affordances leads only to functional explanations, but he still wants to explain, so the burden is on him to come up with a non-mechanistic way to get good quality explanations. His solution is his dynamical explanation papers. In hindsight, all these pieces fit together nicely. However, because we believe we can get to mechanisms and that this is worth doing, it's natural for us to treat affordances as real properties, and it's a nice side-effect that this analysis has let me and others do a lot of detailed empirical affordance research.

I will highlight that I got to meet Erik Reitveld and Julian Kiverstein at EWEP14. I had a lovely chat, and we basically agree on nearly everything around the idea of scaling up ecological (and enactivist) ideas to handle complex cognition. But this problem (that affordances-as-relations create no information, are therefore not perceivable and so can, at best, support functional level analyses of behaviour) remains and I believe it's an important problem they don't actually need to suffer from. Not everything that affects our behaviour is an affordance, and this is just fine. Sabrina's development of the conventional use of information (Golonka, 2015) allows everything they want while preserving the use of real parts and processes, and so I hope we can find a way to align our activities to point in the same basic direction.