Aperiodicity as a Factor in Choice.

  title={Aperiodicity as a Factor in Choice.},
  author={Richard J. Herrnstein},
  journal={Journal of the experimental analysis of behavior},
Four pigeons were trained to peck at either of two response-keys. Pecks at either key occasionally produced a secondary reinforcer, in the presence of which further pecks occasionally produced food, the primary reinforcer. All pigeons showed a consistent preference for variable (as compared to fixed) interval schedules of primary reinforcement.