Fig. 2.

Oral behavior in the testing conditions. Mouth contacts with the spout were detected by means of force transducers (strain gauges). Data from the different variants of each testing condition are ordered from top to bottom. For each condition are shown consecutive and superimposed traces of mouth movement records aligned on the delivery of reward. Data in each condition are shown from 15–20 consecutive trials, the chronological order of trials being preserved from top tobottom. The monkey started to lick the spout on the delivery of reward in the immediate condition and maintained oral activity thereafter, whereas licking movements began before the reception of liquid in the two delayed reinforcement procedures. Mouth movements appeared similar in the irregular and regular 4 sec conditions and consisted of frequent, randomly timed licking movements before the delivery of reward. By contrast, in the regular 2 sec condition, licking movements were restricted to a short time period centered on the receipt of reward so that the movements were performed in synchrony with reward delivery. These mouth movements were recorded simultaneously with neuronal activity.