A pigeon pecks a green key on a VI 60-sec schedule, which results in the insertion of a treadle into the chamber. The pigeon then steps on the treadle 10 times, following which it receives food. This is an example of a(n) schedule of reinforcement.

The correct word for the blank space is: chained.

Explanation:

A chained schedule of reinforcement is set to cause a single response. At least two (2) events or schedules must be arranged in a sequence and after each schedule, there must be a different stimulus. Before the main reinforcement takes place, those events must be completed.

In the case, pecking the grey key and stepping on a treadle are the chained schedules. The length and times the pigeon repeats those activities are the stimulus and receiving food is the primary reinforcement.