Incentive Shifts with Different Massed and Spaced Trial Cues
Rats experienced daily training in an alley with one of two daily sequences of large (L) and small (S) reward trials, SLLL or LSSS. During a given phase of training (pre- or postshift) a rat always experienced the same daily sequence of trials. The four groups were LSSS-SLLL, SLLL-LSSS, LSSS-LSSS, and SLLL-SLLL. One can analyze the data for the groups described above by omitting data from the last three trials of every day of training (massed practice data) or omitting data from the first trial of every day of training (spaced practice data). The spaced practice and massed practice analyses are analogous to the analyses used in conventional incentive shift studies with Groups S-L, L-S, S-S, and L-L. Massed and spaced trials analyses showed faster preshift speeds to large as compared to small reward. These differences in speed were not present early in preshift training. Spaced practice data showed that downward shifted rats did not reduce their speeds. Massed practice data showed that downward shifted rats reduced running speeds slowly. Upward shifted rats (massed or spaced practice) rapidly increased their running speeds. The study suggests that what is learned during spaced trials interacts with what is learned during massed trials.
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