Consider the familiar story of Goldilocks and the Three Bears. When this famous folklore heroine entered the home of the three-member ursine family after having been lost and wandering through the woods for some time, she was desperately tired. Spying a set of three chairs, she decided to sit down to rest. She first tried to sit in the biggest one, but found that it was far too high for her to get onto. She discovered that the second chair was much too wide to be comfortable for her small body. Finally, trying the third, the smallest, chair, she was relieved that it was “just right” for her and promptly sat down.

In Goldilocks’ efforts to seek comfort in the home of the bears, her actions were regulated by her visual recognition that certain of the objects present belonged to the familiar category, “chair.” Having correctly categorized those objects, and feeling fatigued, she went about using them in the standard way. Her initial two attempts to sit down were foiled by the inappropriate size of two of the chairs for a little girl. Only the third was appropriately scaled to the size of her body and therefore (in the terms of Gibson, 1977) offered an affordance for sitting.