ANTICIPATORY CONTRAST AS A FUNCTION OF ACCESS TIME AND SPATIAL LOCATION

Intake of a 0.15% saccharin solution was suppressed when it was follow ed by a 32% sucrose solution in brief daily pairings. With equal acces s durations to the two solutions, intervals of intermediate duration ( 2 or 3 min) produced a larger contrast than more extreme intervals (1 or 10 min). There was no evidence of inhibition of delay with the 10-m in interval (Experiments 1A and 1B). When access times were asymmetric al, longer access time to the first solution reduced contrast, whereas longer access time to the second solution enhanced contrast (Experime nt 2). Contrast was greater when the two solutions were presented at c onsistent and separate spatial locations than when location was change d randomly or when both solutions were presented in sequence at the sa me location. However, a degree of contrast occurred in all conditions (Experiment 3). Experiment 4, conducted with the solutions in opposite arms of a T-maze, showed that anticipatory approach to the location c orrelated with the 32% sucrose solution developed prior to lick suppre ssion on the saccharin solution. However, within daily sessions, there was a reliable increase in contrast without correlated changes in ant icipatory-approach behavior. Access-time effects were attributed to al tered reward values, whereas spatial-separation effects suggest that g oal-directed responses contribute to, but do not cause, anticipatory c ontrast.