Thursday, 3 March 2016

Affordances cognition and decisions

The wall is not to scale
Last night, I went for a pretty typical mid-week run. Near my house is a small wall that provides a handy shortcut, trimming a few metres off my intended route. At the start of the run, when my energy levels are high, I nearly always springboard this small wall; the wall is an affordance for my preferred running route. 

Nothing controversial here I think, I perceive the wall, the wall affords a shortcut for me, I don’t consciously infer anything prior to or during the action, and there is no need to appeal to any cognitive act in my head between perceiving and acting.

Returning the same way forty minutes later, I’ve spent plenty energy and am now tired. I approach the same small wall, but do not to jump over it but instead go the long way round, notwithstanding that it would quicker to take the shortcut. Nothing in the environment that I can detect has materially changed since I was last here forty minutes ago, the wall continues to afford me a shortcut, my goal of taking the shorter route probably looms larger now than before, yet I navigate around the wall and take the longer route. The only explanation seems to reside in me, the subject. That explanation probably goes along the lines of a risk assessment that there is now a greater chance that I might make a mistake (presumably because I’m tired), trip on the wall and fall in a heap. There is a very low probability of this happening, but nonetheless I have little option but to introduce some form of inference to explain the change in action relative to my actions 40 minutes earlier.  There seems to be some cognition now between my perceiving of the wall and subsequent action.

I am struggling to see how ecological psychology might explain this second event. If I was contrasting a fitter 20 year me old against a future 60 year old me in these circumstances, I could posit a change in the relational properties of the wall to me and as my wall-vaulting skills dissipate, it is now longer an affordance to my preferred running route. If it was the first time I was on this route I could consider my lack of environmental familiarity. If I was new to running I could account for it through lack of skill, and with practice, my small wall vaulting skills may augment. Or I could just be tired, so take a low risk option of the pathway for avoidance of injury, for although I might prefer the wall-vaulting shortcut, the longer pathway also offers me the affordance for running. The tiredness of the body is almost certainly part of the cognitive process, so it can be argued persuasively that the cognition (choosing one route over another) is embodied, the body, rather the anything in my head, is helping to solve the task.

Affordance seems to me to be a conceptually useful tool for grounding perception within its environmental constraints. From the perspective of the subject, its relational properties are a helpful framework for guiding what is and is not potential for action based on circumstances, skills and limitations. However, I wonder about its explanatory power. This example is not a troublesome abstract intellectual process, and reflects presumably much of how I navigate trivial locomotion tasks with a number of potential navigation options and outcomes. Yet it’s difficult to understand through ecological psychology alone. There seems to be a need to appeal to a third force, other than perception and action, to explain it.


  1. I think the paper on Umwelt theory describes it well in that the affordance changes based on the "search tone" of the subject. While energised the wall affords jumping over as you search for faster routes, whereas on the way back, as you search for retaining energy resources, the affordances change to that of an obstacle.

  2. Thanks for the feedback Diego.

    Having read the von Uexkull paper now, the "functional tone" does describe well the navigational conundrum above, in a way the ecological psychology is more limited. For von Uexkell, perceptual cues (the wall) are driven by the functional tone in the subjects' umwelt at that moment (time-saving versus energy efficiency). As human sensory complexity allows a greater number of functions, a multitude of effector cues can arise from one perceptual cue. Unlike say the more restricted umwelt of eyeless tick. It does raise the question of what cognitive processes are engaged in selecting which action to pursue in the face of a perceptual cue with multiple potential effector images. It also seems to introduce a third possibility to the Perception-Cognition-Action sequence:

    1. The classic cognitive psychology model of stimulus-response gives rise to P-C-A, where cognition is the machine turning perception into action.

    2. The Gibbsonian model of direct perception or smart perception, which leaves no room for cognition between perception and action. P-A

    3. Umwelt theory -subjects' varying search tones seems to set the cognition (search and recognise for appropriate effector images among perceptual images) before perception. Cognition generates, based on the primary need within the subject's umwelt at that moment, the search tone which on receiving perceptual cues in the umwelt, become the effector image and the basis for action. C-P-A.