Conceptualizing design affordances from a cognitive perspective

Abstract

The term affordance carries multiple meanings for designers. Traditionally, affordances were discussed within a Gibsonian framework as arising from direct perception of physical constraints. However, some authors extended the meaning to include learned cultural constraints, leading to a theoretical debate about whether designers should draw a distinction between perceptual affordances and learned cultural conventions. In this dissertation it is suggested that a broader meaning of affordance is more appropriate for designers and that a unified account of affordances can be achieved using a cognitive conceptualization of perceived affordances. Within this cognitive framework, perceived affordances arise from automatic processes in the user that either are inborn or have developed over time as consistent interactions produce changes in long-term memory. Well learned conventions are examples of the latter. The cognitive mechanisms responsible for how perceived affordances arise and how they affect the cognitive system are presented along with a flowchart to help guide designer decisions. Three experiments examining empirical differences between affordances and conventions are reported. The first experiment asked whether users have developed conventions in the absence of affordances. A simple task was used in which participants pressed buttons in response to directional cues. The results showed that affordances exist when the spatial configuration of the buttons is congruent with directional cues. In the absence of affordances, most participants demonstrated consistent button-to-action mapping that represented a convention. Behavioral differences between affordances and conventions were not found. The second experiment confirmed that in ambiguous tasks, conventions guide expectancies about button-to-action mappings. The cognitive attributes of affordances and conventions were examined in the third experiment by manipulating working memory load and expected interaction congruency. Results indicated some behavioral differences between acting on affordances and acting on conventions. However, violating the button-to-action mappings defining either an affordance or a convention produced similar performance costs. Taken together, the results suggest that after the initial learning period, conventions play a critical role in the perception of a design's available actions, just as do perceptual affordances. Therefore, designers ought to employ perceptual affordances when possible and when that is not feasible reuse established conventions.