The answer is "variable interval.
In operant conditioning, a variable-interval schedule is a schedule of reinforcement where a reaction is remunerated after a capricious measure of time has passed. This timetable creates a moderate, unfaltering rate of reaction.
To see how a variable-interval schedule functions, we should begin by investigating the term itself. Schedule alludes to the rate of support conveyance, or how much of the time the fortification is given. Variable demonstrates that this planning isn't reliable and may fluctuate starting with one preliminary then onto the next. At last, interim implies that conveyance is controlled by time. In this way, a variable-interval schedule implies that support is conveyed at different and erratic intervals of time.