Heft (2001): 3.2, Affordances & Self-Perception

In the next half of Chapter 3, Heft discusses some ideas related to Gibson's notion of affordances, including how it connects with James's radical empiricism and affordances as a prima facie contradictory notion. I've discussed some of my initial thoughts on affordances in this blog, so it'll be interesting to see how these line up with how Heft describes them. The final bit in Chapter 3 touches on the experience of the body in perception, where I'll focus on how the body, like the world, can be directly perceived.

Affordances

For Heft, an affordance is 'a property of the environment that has perceived functional significance for an individual'. For the reader familiar with ecological psychology, this is just another way of saying that affordances are action possibilities offered by the environment to an individual. For now, I'll refer to Heft's definition. There are a few important parts here that are worth diving into. Notice how Heft's definition makes reference to both the environment and the individual. Traditionally, objects of perception are classified according to John Locke's primary and secondary qualities. Primary qualities are those that stay constant regardless of the perceiver in question, such as size and shape. Meanwhile, secondary qualities have a perceiver-dependent quality in that no two individuals experience these qualities (e.g., colour, temperature) in the same way. Given this split, that which is perceived is either an objective primary quality or a subjective secondary one. Gibson rejected this dichotomy when he introduced the term affordances, arguing that affordances are neither purely objective nor purely subjective. This melds well with the neutral substance of pure experience that James introduced in his radical empiricism. In this light, affordances are viewed as percepts, not concepts. That is, they are directly experienced without the need for abstraction or mental categorisation.

Describing affordances in both subjective and objective terms still seems unsatisfactory, though. How can something be objective (i.e., independent of the perceiver) yet subjective (i.e., dependent on the perceiver) at the same time? In the ecological psychology literature, this is represented by the debate between those who see affordances as dispositions and those who see affordances as relations. This debate aside (I support Turvey's dispositional view), let's see how Heft attempts to resolve this apparent contradiction. Heft introduces the idea of potential and actualised affordances. Potential affordances are those which are available in the environment, but not actually acted upon (i.e., perceived or used) yet. In this sense, they are independent of any actor -- one might theoretically be able to describe the potential affordances within an environment. On the other hand, actualised affordances are those which have been acted upon (i.e., perceived or used) by an actor. Using James's notion of knowing as a relation between the perceiver and the world (recall Holt's searchlight analogy of knowing), we might say that with actualised affordances, the actor has entered into a relation with said affordance. 

And this is what it means for affordances to be both objective and subjective! On the one hand, (potential) affordances exist objectively in the environment, regardless of whether or not there is anyone there to perceive them. On the other hand, (actualised) affordances do depend on the perceiver. Whether or not the structure and composition of a step is perceived as step-able or climb-able will depend on whether or not the perceiver is an adult (with the ability to step up on the step) or a child (who might only be able to crawl up the step on all fours). However, irrespective of the presence of any perceivers, the structure and composition of the step constitute the potential affordances of both step-ability and climb-ability! In other words, ontologically, affordances exist as perceiver-independent properties of the environment (potential affordances). Meanwhile, whether and how the affordance is perceived depends on the relevant effectivities of the perceiver (actualised affordances).

The experience of the body in perception

To wrap up Chapter 3, Heft introduces how exteroception and interoception are inseparable. That is, perception of the world is not simply the perception of the world. Instead, perceiving the external environment inherently comes with the co-perception of the self. For example, there is always visual information of the self wherever we look (e.g., the top of your nose, the movement of limbs as we walk) that specifies the self as an embodied agent (unlike Descartes's idea of a disembodied soul). On top of that, the self can be specified with movement-generated information (e.g., self-generated movement allows for visual scenes that are controllable and reversible). 

References

Heft, H. (2001). Ecological Psychology in Context: James Gibson, Roger Barker, and the Legacy of William James’s Radical Empiricism. Psychology Press.