This model uses the commonly observed process of infant development as an analog for the growth of a complex system.
Infants are surrounded by a large, more or less infinite environment of possibilities. But it is in the nature of developing infants that the vast majority of these possibilities are of no interest and do not at any given moment contribute to the infant’s development. Instead only certain parts of the environment are of interest to the infant and these are exactly what the infant needs to engage with in order to further current development.
These parts ready for engagement are called “affordances” because they allow for action by the infant that supports the infant’s current development.
As development continues, those parts of the environment that can act as affordances shift because of the growing competence of the infant and their consequent shift in focus and interest. So, the infant’s “affordance interface” is constantly shifting as development occurs, and exactly tracks the current development of the child.
The deep part of this model is that even if you are 90 years old, you are still doing what the infant is doing, albeit at a different functional level and with a different set of strengths and weaknesses (i.e., a different affordance interface).