Response-duration of lever pressing in the rat

Two aspects of the lever-holding behaviour of rats in a Skinner-box have been analysed: firstly, the changes in the duration of the responses during the acquisition and experimental extinction phase, and, secondly, the bunching of responses during the experimental extinction phase. The response-durations on the first few acquisition trials were found to be bimodally distributed, but to become stabilized at 0.42 seconds as practice increased. During experimental extinction response-durations increased. The rate of increase depended on the conditions of secondary reward. Rats who had the source of secondary reward removed, or restricted, yielded a steeper slope than those who responded under the same conditions of secondary reward as during training.

The analysis of the extinction scores revealed that unrewarded responses were emitted in groups. Response-group latencies were shown to progress as a positive function of the number of response-groups, and the average response-duration for consecutive response-groups to increase progressively. The slope of the duration curve plotted for successive response-groups increased, and this was related to an increase in the value of the time-intercept for successive response-groups.     

A rat lever designed to minimize partial presses

The force required to move commercial spring-loaded rat levers increases with lever displacement. This, characteristic allows the rat to terminate barpresses before they are recorded. Such partial presses are unlikely to occur when the force requirement rapidly decreases as displacement increases. This inverse relationship between force and displacement can be achieved by requiring the rat to lift the tail of the bar out of a magnetic field; the consequence is that the bar “falls out from under” the S, and nearly all movements of the bar result in switch closure. The use of electromagnetic fields provides two additional advantages: the force requirement can be established and monitored remotely.     

A comparison of operant licking and lever pressing in the rat

Two groups of rats were trained on a signaled, free-operant, avoidance procedure to lick or to lever press in order to avoid shock while water-deprived or satiated and, in the case of licking, while ingesting deionized water, isotonic saline, or 10% sucrose. The most effective avoidance licking occurred while the rats were water-deprived and ingesting 10% sucrose. Water deprivation level had no effect on lever pressing for shock avoidance. Two other groups of rats were operantly conditioned to lick or to lever press for food pellets while waterdeprived or satiated and, in the case of licking, while ingesting deionized water or 10% sucrose. The most effective licking for food reinforcement occurred while the rats were water-deprived and ingesting 10% sucrose. Water deprivation level had no effect on lever pressing for food reinforcement. The data indicated that effective operant licking must be supported by factors related to water regulation and taste palatability.     

An easily built and inexpensive apparatus for generating electroconvulsive shock

An easily constructed and inexpensive apparatus for generating electroconvulsive shock is described. The wide range of shock level adjustment and reliability of operation make it an excellent piece of equipment to have in laboratories using electroconvulsive shock as an experimental tool for research on memory and memory storage processes.     

The easily learned,easily remembered heuristic in children

A previous study with adults [Koriat, A. (2008a). Easy comes, easy goes? The link between learning and remembering and its exploitation in metacognition. Memory & Cognition, 36, 416–428] established a correlation between learning and remembering: items requiring more trials to acquisition (TTA) were less likely to be recalled than those requiring fewer trials. Furthermore, learners’ judgments of learning (JOLs) seemed to rely on the easily learned, easily remembered (ELER) heuristic, that items requiring fewer TTAs are more likely to be recalled. This study extended investigation of these effects to 2nd- and 4th-grade children. When the list included hard and easy paired-associates (Experiment 1, N = 40, 7–10 years), recall and JOL decreased with increasing TTAs for both grades, supporting the validity of the ELER heuristic and its utilization in monitoring one's own learning. When presented only with hard pairs (Experiment 2, N = 60, 7–10 years), however, 4th graders’ but not 2nd graders’ JOLs evidenced reliance on this heuristic. The results suggest an early development of metacognitive heuristics that incorporate information about the links between characteristics of the encoding process and subsequent remembering.     

The successive differentiation of a lever displacement response

Maximum displacements of lever presses by rats were recorded under eight successively-smaller reinforcement zones (RZ). The largest RZ included displacements from 3° to 44°; the smallest, from 24° to 29°. As the RZ decreased, displacement distributions reflected a least-effort tendency: distributions peaked at the lower limit of RZ and most non-reinforced presses fell just below the lower limit. Successive distributions (a) differed significantly in shape, (b) showed reduced variability, and (c) indicated more presses and more presses per reinforcement. Prolonged training under the smallest RZ gave no improvement in performance.     

Mental rotation is not easily cognitively penetrable

When participants take part in mental imagery experiments, are they using their “tacit knowledge” of perception to mimic what they believe should occur in the corresponding perceptual task? Two experiments were conducted to examine whether such an account can be applied to mental imagery in general. These experiments both examined tasks that required participants to “mentally rotate” stimuli. In Experiment 1, instructions led participants to believe that they could reorient shapes in one step or avoid reorienting the shapes altogether. Regardless of instruction type, response times increased linearly with increasing rotation angles. In Experiment 2, participants first observed novel objects rotating at different speeds, and then performed a mental rotation task with those objects. The speed of perceptually demonstrated rotation did not affect the speed of mental rotation. We argue that tacit knowledge cannot explain mental imagery results in general, and that in particular the mental rotation effect reflects the nature of the underlying internal representation and processes that transform it, rather than participants’ pre-existing knowledge.     

Suppression of ethanol-reinforced lever pressing by delaying food availability.

When food was initially available to rats under a fixed-interval 26-second schedule and each liquid-reinforced lever press delayed food availability 8 seconds, suppression of liquid-reinforced lever pressing and liquid consumption occurred when the liquid presented was 4, 8, 16, 32, and 0% ethanol. Suppression did not occur in yoked-control animals, which received food coincidentally with experimental animals but were not directly exposed to the delay dependency. After exposure to the food schedule, each ethanol solution served as a reinforcer in the absence of food presentation. Delaying food availability for increasingly long periods (8 to 2048 seconds) suppressed ethanol-reinforced lever pressing and consumption relative to baseline levels, with the maximum decrease being below the level maintained in the absence of food. However, degree of suppression did not increase monotonically with delay length. Liquid-reinforced performance of yoked-control animals indicated that suppression did not result from changes in the sequencing of food presentation alone.     

Narcissistic people cannot be moved easily by visual stimulation

We examined the relationship between personality and visually induced self-motion perception (latency, duration, and magnitude). A psychological experiment with radially expanding patterns that induced self-motion perception along the fore and aft axis was conducted, followed by personality assessments. We found that all the measures of self-motion perception we examined correlated negatively with the degree of narcissistic traits.