This study is concerned with the way in which children's naturally occurring behaviors change over a period of time as they adapt to a nursery school setting. A set of seven varieties of environmental constraints and fourteen adaptations to these constraints was observed among 18 3-, 4-, and 5-year-olds in a nursery school classroom first in the fall, when the setting was newly initiated, and secondly in the spring, when the setting had been in existence for an extensive period of time. The findings showed that duration of the setting was significantly related to changes in several varieties of constraints and adaptations. The results illustrate a basic conception of ecological psychology, that the program of an environment's inputs to individuals changes if its ecological properties change--in this case, if the duration of the setting increases. ED 040 421 is an earlier version of this study. (Author)