RE: Constraints and Affordances

 I am rereading an article right now that might add to our discussion on affordances. I posited in class and in my blog that we should consider affordances  and constraints in our conversation. Here is how Greeno (1998) defines them:

• In situation theory (Barwise, 1993; Barwise & Perry, 1983; Devlin, 1991), constraints are represented formally as if-then relations between types of situations. We use the term constraints to include if-then regularities of social practices and of interactions with material and informational systems that enable a person to anticipate outcomes and to participate in trajectories of interaction. Affordances (E. J. Gibson, 1988; J. J . Gibson, 1979/1986; Reed. 1996) are qualities of systems that can support interactions and therefore present possible interactions for an individual to participate in. Affordances can be represented, using situation-theory notation, as if-then relations between types of situations, in which the antecedent involves resources in the environment and enabling characteristics of a person or group and the consequent is a type of activity that is possible whenever those environmental and personal properties are present. Regular patterns of an individual's participation can be conceptualized as that person's attunements to constraints (Barwise & Perry, 1983) and to affordances. Attunements include well-coordinated panerns of participating in social practices. including the conversational and other interactional conventions of communities (Greeno, et al., p. 9).

These definitions have been very helpful for me, and the concept of learning as becoming attuned to the affordances and constraints of an activity system has been quite formative. 

Greeno, J. G., & Middle School Mathematics through Applications Project Group. (1998). The situativity of knowing, learning, and research. American Psychologist, 53(1), 5–26.