Time limits for completing fixed ratios. III. Stimulus variables

Pigeons received food only if they took longer than a specified time to begin and complete a fixed ratio. In Experiment 1, ratios with shorter durations had no stimulus consequence; in Experiment 2, these ratios ended with a stimulus change. In both studies, the mean time to complete the ratio exceeded requirements of less than 30 sec, approximately matched requirements of 30 sec, and fell progressively short of matching thereafter. Variability increased together with the means. The various effects resembled those of temporal differentiation experiments involving single responses. Although both number of ratios and time separating successive food presentations increased along with ratio duration, control experiments showed that differential reinforcement of duration, rather than either form or reinforcer intermittency, accounted for the performance. Experiment 2 also studied the effects of adding a stimulus that signalled when the required time had elapsed. The stimulus produced durations that matched even the most stringent requirements. This precision was not maintained when the stimulus was removed. Temporal differentiation schedules seem to have similar effects regardless of the response class and temporal property involved.     

Time limits for completing fixed ratios. II. Stimulus specificity

Pigeons were exposed to two stimuli that were each correlated with the same fixed-ratio schedule. During one stimulus, the ratio had to be completed in more than a specified time for food to be presented. During the other, the ratio had to be completed in less than a specified time. Failures to meet the time criterion produced a timeout and reset the ratio. Treating the entire behavioral sequence generated by a fixed-ratio schedule as a unitary response and scheduling differential reinforcement with respect to the duration of the sequence produced effects comparable to those observed previously with individual responses. The times taken to complete the ratios conformed to the time criteria under both stimulus conditions. Similar effects have been observed with differential reinforcement of the duration of individual responses and in experiments specifying running speed criteria under discrete trial conditions.     

Time limits for completing fixed ratios. IV. Components of the ratio

Pigeons received food after completing a fixed ratio if the temporal properties of responding exceeded minimum duration requirements. In one set of conditions, a minimum time had to elapse before the first response of the ratio (the initial pause). In another set, the minimum duration was the time between the first and last response of the ratio. Obtained times increased as a power function of required times in both conditions. The power function resembled that occurring in experiments involving temporal differentiation of individual responses, interresponse times, latencies, and entire fixed-ratio sequences. Moreover, in all of these experiments individual performances could be described as a function of the base duration (the duration occurring in the absence of temporal requirements) and the specific time requirement. Control conditions indicated that the effects resulted from temporal requirements and not from reinforcer intermittency.     

Escape behavior under different fixed ratios and shock intensities

The effects of ratio length and shock intensity on bar pressing were examined in three rats in two escape-from-shock experiments. In Experiment I, shock intensity was held constant while the schedule was varied from FR 1 to FR 20. The latency of the first escape response increased with FR length while the escape rate, computed as over-all rate in shock minus latency of the first response, decreased at FR 20. In Experiment II, the schedule was held constant at FR 5 while shock intensity was manipulated. Latency decreased as intensity increased, while escape rate increased with intensity, passing through a maximum for two subjects. Responses occurring during the last 100 sec of the 2-min escape period decreased as the FR increased for all subjects, and decreased as shock intensity increased for two subjects.     

Effects of fixed and variable ratios on human behavioral variability.

The effect that ratio schedules of reinforcement had upon variability of responding was investigated in college students. Subjects were paid $0.02 contingent upon completion of eight presses, distributed in any combination across two push buttons; 256 different sequences were possible. Sequence emission was reinforced according to fixed- and variable-ratio schedules. Ratio requirements of 1, 2, 4 and 8 were presented in alternate components of a multiple schedule. The variability engendered by variable-ratio schedules was also compared to that engendered by fixed ratios. Variability increased with ratio size, irrespective of whether the schedule requirement was fixed or variable. The data demonstrate the similarity between the determinants of human and nonhuman variability, and they illustrate the role of ratio size in determining variability in operant behavior.     

A fixed rehearsal capacity interpretation of limits on absolute identification performance

The information transmitted in absolute identification quickly reaches its upper limit as the number of (one-dimensional) signals, and their range, is increased. Several explanations have been given of this phenomenon, but all are ad hoc in one way or another. Here we present a ‘memory’ or ‘rehearsal’ interpretation. The basic (psychological) representation of each signal in an absolute identification experiment is assumed to be quite accurate, and independent of the other stimuli used in the experiment. However, the identification of the stimulus presented on a particular trial is relative to a ‘frame’ (usually the range of stimuli in that experiment) that the subject must ‘rehearse’ using a fixed capacity rehearsal system. In special cases, this model reduces to earlier suggestions, but its general motivation seems somewhat less ad hoc than that of earlier ideas, and it is also easily applied to the absolute identification of multivariate signals and to magnitude estimation.     

Time limits and gender differences on paper-and-pencil tests of mental rotation: a meta-analysis

The purpose of this study was to summarize research relevant to the influence of time limits on gender differences in paper-and-pencil tasks of mental rotation by means of a meta-analysis. Thirty-six effect sizes from published and unpublished studies examining the influence of time constraints were retrieved. Results showed that gender differences in mental rotation are significantly larger when the task is administered with time constraints compared to when such constraints are absent. In addition, the magnitude of gender differences was linearly related to the amount of time available for test completion. These findings were not related to the age or the year of birth of participants in the retrieved studies. The results are discussed with regard to their implications for explanations of gender differences in mental rotation and cognitive abilities in general.     

Time and resource limits on working memory: cross-age consistency in counting span performance

This longitudinal study separated resource demand effects from those of retention interval in a counting span task among 100 children tested in grade 2 and again in grades 3 and 4. A last card large counting span condition had an equivalent memory load to a last card small, but the last card large required holding the count over a longer retention interval. In all three waves of assessment, the last card large condition was found to be less accurate than the last card small. A model predicting reading comprehension showed that age was a significant predictor when entered first accounting for 26% of the variance, but counting span accounted for a further 22% of the variance. Span at Wave 1 accounted for significant unique variance at Wave 2 and at Wave 3. Results were similar for math calculation with age accounting for 31% of the variance and counting span accounting for a further 34% of the variance. Span at Wave 1 explained unique variance in math at Wave 2 and at Wave 3.     

Capacity limits for face processing

We present three experiments in which subjects were asked to make speeded sex judgements (Experiment 1) or semantic judgements (Experiments 2 and 3) to face targets and nonface items, while ignoring a solitary flanking distractor face or a nonface stimulus. Distractors could be either congruent (same response category) or incongruent (different response category) with the target. Distractor congruency effects were consistently observed in all combinations of target-distractor stimulus pairs, except when a distractor face flanked a target face. The failure to find congruency effects in this condition was explored further in a fourth experiment, in which four task-irrelevant flankers were simultaneously presented. Once again, no face-face congruency effects were found, even though comparison distractors interfered with face and nonface targets alike. However, four simultaneously presented distractor faces did not interfere with nonface targets either. We suggest that these experiments demonstrate a capacity limit for visual processing in these conditions, such that no more than one face is processed at a time.     

Prediction of adolescents doing physical activity after completing secondary education

The purpose of this study, based on the self-determination theory (Ryan & Deci, 2000) was to test the prediction power of student's responsibility, psychological mediators, intrinsic motivation and the importance attached to physical education in the intention to continue to practice some form of physical activity and/or sport, and the possible relationships that exist between these variables. We used a sample of 482 adolescent students in physical education classes, with a mean age of 14.3 years, which were measured for responsibility, psychological mediators, sports motivation, the importance of physical education and intention to be physically active. We completed an analysis of structural equations modelling. The results showed that the responsibility positively predicted psychological mediators, and this predicted intrinsic motivation, which positively predicted the importance students attach to physical education, and this, finally, positively predicted the intention of the student to continue doing sport. Results are discussed in relation to the promotion of student's responsibility towards a greater commitment to the practice of physical exercise.     

Developing probability limits for longitudinal physiological data

The objective of this study was to determine what amount of change in heart electrophysiology is necessary to yield a significant difference between a baseline condition and an experimental treatment condition. In a single-subject longitudinal design, a modification of at test was applied to baseline data, and the performance levels for both .05 and .01 probability levels were obtained. It was concluded that it is both ethically sound and physiologically safe to permit a subject in this type of experiment to physiologically respond at levels that would reach both the .05 and the .01 levels of significance.     

Signal/noise ratios for domain-referenced tests

Using the assumption of randomly parallel tests and concepts from generalizability theory, three signal/noise ratios for domain-referenced tests are developed, discussed, and compared. The three ratios have the same noise but different signals depending upon the kind of decision to be made as a result of measurement. It is also shown that these ratios incorporate a definition of noise or error which is different from the classical definition of noise typically used to characterize norm-referenced tests. Part of the work leading to this paper was accomplished while the authors were assistant professors at the State University of New York at Stony Brook.