Laurence Miller

Stimulus compounding with an instrumental avoidance response

A light and buzzer each separately maintained a latency of response which avoided shock in a shuttle box. When the light and buzzer were compounded, the latency was significantly shorter than the latency to either single stimulus. This result reliably occurred only with Ss that had a high percentage of avoidance responses and fairly, short latencies to the single stimuli The results were interpreted in terms of summation of response tendencies.

Acquisition of Lever Pressing by Rats with and without Magazine Training

Four groups of five rats each were given the opportunity to acquire lever pressing without direct experimenter assistance. Subjects in Groups 1 and 2 were first given prior magazine training with the levers retracted and the next day were presented with one or two levers, respectively. Each lever press produced a food pellet. Subjects in Groups 3 and 4 were exposed directly to one or two levers, respectively, without prior magazine training. Three of five rats in Groups 1, 3 and 4 and all rats in Group 2 acquired lever pressing within a single hour session.

Stimulus compounding and response summation with an instrumental running response

A light and a tone each maintained a certain speed of an instrumental running response in a straight alley. When the light and tone were combined, their compound maintained a faster running speed than that maintained by either the light or tone alone. The results were interpreted in terms of summation of the response tendencies maintained by each stimulus and further demonstrated the wide generality of this phenomenon.

Compounding of discriminative stimuli from the same and different sensory modalities which maintain responding on separate levers

Rats barpressed for food during light or tone or two separate lights. Each stimulus maintained responding on a separate lever. In Phase 1, one lever and its correlated stimulus appeared during a session. In Phase 2, both levers were concurrently exposed and each stimulus appeared. When light and tone were combined in Phase 1, responding increased with either lever exposed. Responding also increased during compounding in Phase 2, but nearly all responses occurred on the light-correlated lever. When the two lights were combined in Phase 1, no change in responding occurred with either lever present, regardless of the intensity of each light. No change in responding also occurred during compounding in Phase 2 with lights of different intensity. However, responding increased significantly with lights of equal intensity. There was no significant difference in the number of responses emitted on each lever with either set of intensities.

Compounding of Discriminative Stimuli Maintaining Topographically Different Instrumental Responses

Summary Rats traversed a runway and lever pressed in the same runway for food on alternate days in the presence of either light or tone, and did not receive reinforcement in the absence of these stimuli. When the stimulus correlated with running was combined with the stimulus correlated with lever pressing, while Ss lever pressed, level of responding increased significantly. When the stimulus correlated with lever pressing was combined with the stimulus maintaining running, while Ss ran, running speed either did not change or was nonsignificantly reduced. Also, latency of running either did not change or was nonsignificantly increased. It was further shown that summation occurred when each stimulus was correlated with the identical response and same or different reinforcement schedule, and when each stimulus was presented either during the same session or during alternate sessions only. The results suggest transfer of stimulus control with topographically different instrumental responses maintained by app...

The Effect of Signaled Response-Independent and Response-Dependent Reinforcers on Responding Maintained by a Variable-Interval Schedule

A light was correlated with either a fixed-time (FT) 10-sec. or fixed-interval (FI) 10-sec. schedule. With FT the light was terminated after 10 sec. and a response-independent food pellet was presented. With FI the first response emitted after 10 sec. produced a food pellet. These schedules were presented intermittently while operant lever pressing by rats was maintained on a variable interval schedule in the absence of the light. The probability that the termination of the light was correlated with a reinforcer and the likelihood that variable interval reinforcers could be obtained during the light were manipulated. The level of responding during the light was most likely to exceed the level of responding in the absence of the light when variable interval reinforcers occurred during the light or when an FI 10-sec. schedule was in effect. The level of responding was not affected significantly when no variable interval reinforcers occurred during the light and the light was correlated with FT 10-sec. The data suggest that facilitation of responding during the light was caused by a contingency between responding and the reinforcer correlated with the light’s termination.

Free recall of trigrams following their presentation in a short-term memory task

Ss free recalled items they had previously separately verbally recalled in a standard short-term memory task. Free recall was examined as a function of: (1) order of item presentation, (2) length of retention interval, (3) presence or absence of an instructional set to recall all items, and (4) activity during the intertrial interval. Significant effects due to order of item presentation, intertrial-interval activity, and interactions between order of presentation and intertrial-interval activity and between presentation order and instructions were found. A recency effect appeared in all instances, but a primacy effect was obtained only when Ss were forewarned of free recall. The effect of intertrial-interval activity was most evident with the last item. Rehearsal of the item produced better recall than either counting or doing nothing, but counting produced better recall than doing nothing.

The effect of duration of item exposure on recall in a short-term memory paradigm

Ss were tested for recall of six consonant trigrams at retention intervals of 0, 3, and 18 sec with a 2,000-, 500-, or 200-msec duration of item exposure. As duration was reduced, retention at 3- and 18-sec within- and between-exposure durations declined for all items, and the interaction between length of retention interval and number of items was significantly reduced for the initial and middle items. The results were interpreted in terms of increased proactive interference as item exposure was reduced.

The Effect of Instructional Set and Intertrial Activity on Retention in a Short-Term Memory Task

These experiments investigated the effects of intertrial activity and instructional set on recall of consonant trigram stimuli in a short-term memory task. Subjects either: (a) sat silently during the intertrial interval; (b) overtly rehearsed the prior item during the intertrial interval; (c) overtly rehearsed the prior item under a set that they were to recall all items; (d) were given the set and engaged in a neutral counting activity during the intertrial interval; (e) counted during the intertrial interval with no set. Overt rehearsal and set, singly and togther, depressed recall over a 3- and 18-sec retention interval and largely eliminated differences in recall between the two intervals. Counting during the intertrial interval depressed recall of the initial and middle items.

External and internal control of fixed-ratio responding as assessed by stimulus compounding

In Phases 1 through 3 light or tone was correlated with the initial or terminal portions of fixed-ratio schedules in order to examine the control exerted by external and internal stimuli. Control was assessed by means of stimulus compounding: The stimuli correlated with the initial and terminal portions were combined during the initial and terminal portions of the schedule. Control was also assessed by removing the external stimuli entirely. In Phase 4 light or tone was correlated with the entire fixed ratio and a variable-duration time-out occurred after each ratio. Control was also assessed by combining light and tone. The results of the four phases generally suggested weak external control and much stronger internal control of fixed-ratio responding.