Differences in visual sensitivity among mindfulness meditators and non-meditators

Tachistoscopic presentation of light flashes was used to test for differences in visual sensitivity among 3 groups of practitioners of Buddhist mindfulness meditation and non-meditator-controls. Meditation practitioners were able to detect light flashes of shorter duration than the non-meditators. There were no differences among the meditator groups. There were no differences among the groups in ability to discriminate between closely spaced successive light flashes. The lower detection threshold for single light flashes for the meditators may reflect an enduring increase in sensitivity, perhaps the long-term effects of the practice of mindfulness meditation on certain perceptual habit patterns. The lack of significant differences in the discrimination of successive light flashes probably reflects the resistance of other perceptual habit patterns to modification. The results support the statements found in Buddhist texts on meditation concerning the changes in perception encountered during the practice of mindfulness.     

Functional equivalence between same-different classifications and judged similarity of Markov patterns

This experiment represented an initial at tempt at comparing same-different classifications and similarity judgments of Markov histoforms sampled from three different schema families. A measure of individual stimulus variability was more strongfy related to classification responses than to judged similarity. Dichotomous responses, derived from the similarity data by imposing threshold criteria, were found to be highly similor to real classification responses when the threshold values were estimated directly from the latter; little correspondence, however, was obtained using optimal classification criteria. The results support the notion that somewhat different features are used in making classification responses and similarity judgments, and indicate the need for developing more sensitive tasks involving controlled scanning of pattem information.     

Visual and tactual form discrimination: Psychophysical comparison within and between modalities

Intermodal perceptual equivaience was investigated, using visual and tactual oddity discrimination and cross-modal matching-to-sample tasks. Four groups of Ss were presented with 100 problems made up of randomly derived forms from five levels of sidedness. The same quadratic relationship was observed for all tasks as a function of complexity, with optimal performance at eight sides. Comman information utilization, as indicated by intercorrelations of performance variables and by correlational analyses with differences in form measures, was not as pronounced within side classes. Evidence concerning the nature of pattern-feature usage in discrimination was obtained from graphical analyses.     

Schematic concept formation: Feature measures and constraint redundancy as predictors

Constraint redundancy (R_c) was varied in order to manipulate the statistical structure of sets of patterns. Measures of pattern features and R_c were related to the categorization by Ss who had experienced different types of preexposure to sets of patterns from the same stimulus domain. Both R_c and pattern measures were related to the categories produced by Ss in a schematic-concept-formation (SCF) task.     

Recognition assessed by D' and by a non-parametric alternative (the A-index) as a function of the number of choices

Freedom from restrictive assumptions and ease of psychological interpretation are two basic criteria for a satisfactory measure of recognition performance. The A-index (Brown, 1965a) comes close to fulfilling these criteria. It is based on the proportion of wrong choices rejected in a multi-choice test as revealed by the number of choices required to select the correct choice. It can be transformed into the d' measure of signal detection theory (SDT) if the standard assumptions of this theory hold, but not in general. Two experiments on the recognition of words-in-noise are described. In the first there were 3, 5, 8 or 16 choices. They were typed on a card which was displayed to the listener during the presentation of a word. On both measures 5-, 8- and 16-choice recognition did not differ significantly, while 3-choice recognition was slightly, but significantly, superior. The second experiment concerned the effect of delaying the display of the card until 2 sec. after presentation. No evidence for an effect was obtained. In both experiments, there was suggestive but not conclusive evidence that the d' measure tended to overestimate recognition efficiency.     

Prior stimulation and the perception of causality

An attempt was made to discover whether, in conditions similar to those of Michotte, the number of causal responses given by subjects was influenced by stimulation during the period just before the main experiment. Time-intervals between the arrival of object A and the departure of object B were systematically varied within the range 60 to 390 msec. Those who had earlier been exposed to shorter time-intervals (60 to 210 msec.) gave fewer causal responses than those who had been exposed to longer ones (150 to 300 msec. and 240 to 390 msec.). A possible explanation is offered in terms of the modification of existing “schemata.”     

d-Amphetamine-chlorpromazine antagonism in a food reinforced operant

Dose effect curves for d-amphetamine and chlorpromazine were obtained with rats on a milk reinforced FR 10 schedule. A dose of d-amphetamine (2.5 mg/kg, i.p.) which completely suppressed all responding for 60 min was administered simultaneously (concomitant with the pretreatment times) with various doses of chlorpromazine. The d-amphetamine-induced cessation of responding was removed by several of the doses of chlorpromazine with maximal antagonism occurring at a dose of 1.5 mg/kg i.p. This dose of chlorpromazine, when administered independently, produced no observable side effects and showed no effect on the FR 10 schedule. One animal appeared to develop tolerance to the repeated dosages of d-amphetamine.     

The effect of prior recall on multiple response recognition

Certain investigators have found that recognition is impaired when a recall test is interpolated during the retention interval. One possible explanation of this finding is that interpolated recall leads subjects to employ a more stringent recognition criterion. In the two experiments reported here, the influence of the recognition criterion was eliminated by using a multiple-response test requiring subjects to rank a recognition list consisting of old and new items. Nevertheless recall impaired subsequent recognition in both experiments, the effect being most marked for lowly ranked items. The recognition test in the first experiment was carried out in two stages. This made possible a direct examination of whether recall has an effect on the recognition criterion. No evidence for such an effect was obtained. Other ways in which recall may affect the recognition criterion are discussed.