Distribution of practice and the Müller-Lyer illusion1

Two experiments were conducted to determine the influence of distribution of practice on the decrement of the Muller-Lyer illusion. In the first experiment, Ss judged the illusion figure 100 times per session in five sessions separated by intervals of seven days. In the second, Ss judged the figure 200 limes in a single session. The data were compared with those from an earlier experiment (Dewar, 1967) in which Ss judged the figure 100 times per session in five sessions separated by 24 h. In all three experiments two configurations of the illusion were used-one with a 60° angle between the obI ique lines and one with a 120° ang Ie. The distribution of practice did not influence the decrement of the illusion for the 120° figure. The only effect of this variable was to produce a more rapid practice decrement for the 60° figure when sessions of 100 trials were separated by a 24-h intewal.     

"Shaping" of frequency discrimination performance using only intrinsic reinforcement.

This experiment compared two modes of practice at a difficult frequency discrimination, i.e., one in which the frequency difference was initially correctly discriminated only 65% of the trials in a two-alternative forced-choice task. One group of Ss (N = 13) was assigned to a progressive-practice group, in which the frequency difference to be discriminated was progressivley changed from a large, easy, difference to the difficult, small, difference. The other group of Ss (N = 13) received the same amount of practice as the first, but all at the difficult discrimination. Only the progressive-practice group improved their discrimination performance. Since no feedback was given, the effect of progressive practice is interpreted as "shaping" Ss' attentional response by virtue of the information provided by the successively more difficult discriminations. This "shaping" process is potentially available as a learning mechanism for other fine discriminations.     

Effect of subliminal stimuli on consumer behavior: negative evidence.

The study corrected methodological weaknesses found in previous experiments designed to test the contentions of motivational research theorists that subliminal stimulation can affect buying behavior. The words "Hershey's Chocolate" were presented to a group of 18 experimental Ss below a forced-choice detection threshold. The 19 control Ss had a blank slide superimposed over the same background media. In a highly controlled buying situation neither experimental nor control Ss purchased Hershey's products, but on comparable chocolate products, the experimental Ss bought 5 and the control Ss, 3. A second study tested 15 experimental and 12 control Ss with the stimulus presented just below a recognition threshold. No experimental Ss bought Hershey's; two control Ss did. No support was found for the claims of motivational research theorists.     

How repeatable are Stevens’s power law exponents for individual subjects?

Magnitude estimations of apparent length and apparent area were obtained for the same group of Ss over successive experimental sessions. Session-to-session correlations between individual exponents on a given continuum were positive and reliable for successive 24-h intersession intervals, but were not significant for a 1-year interval. In a second experiment on judgments of apparent area, when each stimulus was judged only once per session, the session-to-session correlation was reliable only when the intersession interval was zero. Six other intervals, ranging from 1 to 77 days, yielded nonsignificant correlations. When the constraints exerted by repeated judging are removed, the location of S’s exponent in a distribution of exponents is stable only for brief intervals. Thus the differences among exponents cannot reflect any persisting attributes of Ss’ sensory or judgmental processes.     

Proportional and nonproportional transfer of movement sequences

Two experiments were designed to determine participants' ability to transfer a learned movement sequence to new spatial locations. A 16-element dynamic arm movement sequence was used in both experiments. The task required participants to move a horizontal lever to sequentially projected targets. Experiment 1 included 2 groups. One group practised a pattern in which targets were located at 20, 40, 60, and 80° from the start position (long sequence). The other group practised a pattern with targets at 20, 26.67, 60, and 80° (mixed sequence). Both groups were tested 24 hours later on the long, mixed, and short sequence. The short sequence was considered a proportional transfer for the long acquisition group because all the amplitudes between targets were reduced by the same proportion. Nonproportional transfer occurred when the amplitudes between targets did not have the same proportions as those for their practice sequence (e.g., long sequence to mixed sequence or vice versa). The results indicated that participants could effectively transfer to new target configurations regardless of whether the transfer required proportional or nonproportional spatial changes to the movement pattern. Experiment 2 assessed the effects of extended practice on proportional and nonproportional spatial transfer. The data indicated that while participants can effectively transfer to both proportional and nonproportional spatial transfer conditions after 1 day of practice, they are only effective at transferring to proportional transfer conditions after 4 days of practice. The results are discussed in terms of the mechanism by which response sequences become increasingly specific over extended practice in an attempt to optimize movement production.     

Proportional and nonproportional transfer of movement sequences

Two experiments were designed to determine participants' ability to transfer a learned movement sequence to new spatial locations. A 16-element dynamic arm movement sequence was used in both experiments. The task required participants to move a horizontal lever to sequentially projected targets. Experiment 1 included 2 groups. One group practised a pattern in which targets were located at 20, 40, 60, and 80° from the start position (long sequence). The other group practised a pattern with targets at 20, 26.67, 60, and 80° (mixed sequence). Both groups were tested 24 hours later on the long, mixed, and short sequence. The short sequence was considered a proportional transfer for the long acquisition group because all the amplitudes between targets were reduced by the same proportion. Nonproportional transfer occurred when the amplitudes between targets did not have the same proportions as those for their practice sequence (e.g., long sequence to mixed sequence or vice versa). The results indicated that participants could effectively transfer to new target configurations regardless of whether the transfer required proportional or nonproportional spatial changes to the movement pattern. Experiment 2 assessed the effects of extended practice on proportional and nonproportional spatial transfer. The data indicated that while participants can effectively transfer to both proportional and nonproportional spatial transfer conditions after 1 day of practice, they are only effective at transferring to proportional transfer conditions after 4 days of practice. The results are discussed in terms of the mechanism by which response sequences become increasingly specific over extended practice in an attempt to optimize movement production.     

An Examination of the Selection of Criterion Scores for the Study of Motor Learning and Retention

150 Ss were given 50 practice trials on the stabilometer over a period of 4 days (20 trials on Day 1 followed by a 1-day rest, 10 trials on Day 2, followed by a 7-day rest, 10 trials on Day 3 followed by a 14-day rest, and 10 trials on Day 4). A series of learning scores reflecting improvement in performance over the 4 days and retention scores reflecting loss of performance between days were obtained. The reliability of individual differences in these scores were calculated using the odd-even method and by progressively increasing the number of trials included in the measure of initial and final performance level. On the basis of the findings obtained it was concluded that using 4 – 6 trials in initial and final ability levels results in a difference (criterion) score which combines relatively high reliability with a relatively high estimate of the amount of change in performance.     

The role of balance dynamics in the active perception of orientation.

The Stoffregen and Riccio (1988) hypothesis that perceived orientation is determined primarily by balance dynamics was tested. Perception of orientation was evaluated in the context of a task that required Ss to control the roll orientation of a device in which they were seated. The device's direction of balance was manipulated across trials and thus was independent of gravity. Eighteen Ss participated in the investigation. After each trial, Ss estimated their mean tilt with respect to upright. Correlations of perceived tilt with tilt from balance were consistently higher than the correlations with gravity tilt. The dominance of balance over gravity depended on the magnitude of tilt from balance.     

The Influence of Competition on the Efficiency of an Isometric Muscle Contraction

36 male Ss from collegiate intramural athletic teams were asked to maintain 50% of their maximum voluntary contraction on an iso-metric handle as long as possible. Ss were divided into 2 groups. One group performed individually while the other group, in teams of 3 Ss each, competed for a team prize. During the session, the active muscle was continuously monitored by EMG. The introduction of the motivational factors of competition and team presence did not increase the mean endurance time, but muscle EMG activity was significantly increased when additional motivational factors were introduced. It was concluded that team presence and competition are better described as stress factors which reduce the efficiency of the muscles. The reduction of efficiency is explained both in terms of increased activity of the antagonistic muscles and an increase in S’s general arousal level.     

Sex differences in personality and expectancy

It has been shown that women have a lower expectancy than men before examinations, without there being any differences in past performance levels or in work spent in exam preparations. It was proposed that these sex differences in expectancy could be understood as an expression of differences in instrumental/expressive personality dispositions. In a group of undergraduate psychology students tested a short time before examination, scores on a composite index called “Strong” were found to account for a significant but small amount of variance in expectancy estimates. The relationship between expectancy and Strong was also found to depend on the level of another composite index called “Warm.” A fairly high correlation between expectancy and Strong was thus found for Ss describing themselves as warm. For Ss describing themselves as not very warm, no relationship between expectancy and Strong was found. When differences in personality traits were controlled, however, women were still found to have a lower expectancy than men. Expectancy was found to be a more accurate predictor of actual grades for Ss with high scores on instrumental traits than for Ss with low scores.     

The effects of reinforcement and social approval on conforming behaviour

The effects of reinforcement, social approval and sex on conformity were studied. Seventy-two male and 72 female college Ss were divided into equal high and low need for social approval groups. Each group was assigned to 1 of 3 experimental conformity conditions: (a) True-agree; (b) neutral; and (c) true-disagree. The groups were tested via a social conformity apparatus. It was found that: (a) Reinforcement for agreeing with a contrived group consensus (true-agree group) elicited more conformity than social pressure without reinforcement (neutral group), which in turn elicted more conformity than reinforcement for disagreeing with the consensus (trueA- disagree group); (b) females conformed more than males; (c) there was a slight tendency for high social approval Ss to conform more than low social approval Ss. Conformity was explained in terms of social learning, and it was suggested that the situational factor of reinforcement was a more important determinant of conformity than the motivational factor of social approval. The modified conformity scoring procedure used focuses on the conformity process.     

A laboratory task for induction of mood states

One hundred female college students were administered the Harvard Group Scale of Hypnotic Susceptibility, Form A, to provide a measure of primary suggestibility. In a 2nd hr, each S was randomly assigned to one of five individual treatments of 20 Ss each. One group read and concentrated upon 60 self-referent statements intended to be elating: a second group read 60 statements intended to be depressing. A third group read 60 statements which were neither self-referent nor pertaining to mood. This group controlled for the effects of reading and experimental participation per se. Fourth and fifth groups received demand characteristics control treatments designed to produce simulated elation and simulated depression, respectively.

Two measures of pre-treatment mood level were obtained from each S at the beginning other individual treatment. Following treatment, as criteria for elation and depression, seven behavioral task measures were obtained. Four of these distinguished significantly among the treatment groups. The comparative performance of Ss in the three control groups indicated that the obtained mood changes could not be attributed to artifactual effects. Moreover, post-experimental questionnaire data strongly supported the conclusion that Elation and Depression treatments had indeed respectively induced elation and depression.     

Looking time: The effects of stimulus complexity and familiarity

During a 10 min. stimulus familiarization period, three groups of 60 Ss each received either 0, 10, or 20 sec. of familiarization on each of 30 experimental stimuli: 10 each of low, medium, and high stimulus complexity. All Ss then viewed the experimental stimuli in a second task, during which they could look at each stimulus for as long as they wished (free looking). For half the Ss in each group, free looking was administered immediately after the familiarization period. The remaining Ss received free looking 48 hr. later. The results replicated earlier research which has shown that free looking time is inversely related to stimulus familiarity, and directly related to stimulus complexity. Unlike earlier findings, the data suggested that with a 48 hr. delay between familiarization and free looking, a stimulus can, at least partially, recover from the decrement in looking time produced by 10 sec. of familiarization.     

Efficiency of Learning as a Function of Practice Schedule and Initial Ability

2 groups of 50 Ss practiced a pursuit rotor skill under different schedules of practice. A massed practice (MP) group (40 sec. work, 20 sec. rest) performed just as well as a distributed practice (DP) group (20 sec. work, 20 sec. rest) on the first day of practice. However, after 24 hr. of interpolated rest MP Ss demonstrated significantly greater amounts of learning. A further analysis of the 15 high initial ability and 15 low initial ability Ss from each of the two main groups resulted in no statistical differences among these subgroups in Day 1 performance that could be attributed to the practice schedules; however, a significant Ability Level × Practice Schedule interaction was obtained for Day 2 performance. It was caused by the low ability Ss under MP learning relatively more than the high ability Ss under MP when compared to the two DP groups. Thus learning was seen as being a function not only of schedule of practice but also of initial ability level.     

Encoding differences in recognition and recall

After practice consisting of the free recall of five blocked categorized lists, Ss were presented a sixth list and then unexpectedly tested for recognition. After practice at recognition of the same five lists, Ss were unexpectedly tested for recall following presentation of the sixth test. Recognition performance was superior when items were encoded in anticipation of a recognition test. Intracategory serial position functions for Ss anticipating recall tests were different from those anticipating recognition tests regardless of the retention test employed. The role of control processes in recall and recognition testing is discussed     

Ego Disjunction as a Factor in Intersexual Attraction

The influence of individuals' intrapsychic motivational conflicts on intersexual dyad formation was investigated. Both members of 71 engaged couples served as Ss. Motivational conflict was assessed with two indices of ego disjunction, one developed by Trehub and the other derived by the present authors from the Trehubian model. Low albeit significant positive correlations were found between the scores of male and female Ss. These results are interpreted as indicative of a modest tendency for persons high in motivational conflict to be attracted to one another.     

Interrelations of perceptual reports of smell,taste and irritance over the near-threshold range,for members of the N-aliphatic monohydric alcohol series

Many compounds are psychophysically complex because they stimulate all three chemical senses; smell, taste, and irritance.3 Interrelations among these three modalities are reported over the near-threshold range, and comparisons are made for three such compounds; methanol, ethanol, and propanol. Eighteen Ss were tested over 16 sessions each under a range of conditions: a combined task condition that approximated normal drinking, in which thresholds for all three modalities were determined simultaneously, and three conditions, in each of which only one threshold in one modality was determined. Pooled results over Ss gave significant shifts in olfactory thresholds between conditions, whereas changes in gustatory and irritant acuity were less marked. Individual results yielded significant correlations between psychophysical behavior and personality measures. Factor analysis of Ss indicated the existence of subgroups of Ss, each typified by different patterns of relative sensitivity over modalities and over alcohols.     

Minding the Dreamer Within: An Experimental Study on the Effects of Enhanced Dream Recall on Creative Thinking

Several studies have found an association between frequency of dream recall and creativity. We tested the hypothesis that training individuals to increase dream recall by means of a daily dream log would increase scores on the Torrance Test of Creative Thinking (TTCT). One hundred twenty‐five participants completed a baseline measure of creativity (TTCT, figural version) as well as of dream recall, dissociation, thinness of psychological boundaries, mindful‐attention awareness, and well‐being. Participants were randomly allocated to two groups: the experimental group (n = 55) received a daily dream log; while the control group (n = 32) received a similarly phrased log registering memories of a vivid episode from the previous day. After 27 days, all participants completed follow‐up measurements identical to those at baseline. A non‐randomized non‐intervention group (n = 35) was used to test for practice effects on the TTCT. There was significant selective increase for the “creative strengths” component, which was only observed in the experimental group. There were significant correlations between creativity and dissociation as well as between creativity and thinness of psychological boundaries. Enhanced dream recall through daily dream logging fosters aspects of creativity. Associations between creativity, dissociation, and thinness of boundaries, suggest that increased awareness to dreams increases creativity through a “loosening” of stereotyped thinking pattern.     

A method for determining the aversive threshold in the rat using repeated measures: Tests with morphine sulfate

The procedure described here provides an objective automated technique for the psychophysical assessment of the aversive threshold and allows the animal Ss to serve as their own controls. Sensitivity to drug effects, as well as comparisons between drugs, using the same animals are possible also. Using a rectangular tilt cage, the aversive threshold to grid shock was defined as that intensity avoided 75% of the time. Each shock intensity (30, 60, 90, 120, and 150 microA) was presented for 5 min on one side of the cage and then switched to the other side for 5 min, thereby forcing the animal to sample each shock intensity. Aversive thresholds were determined daily for each rat. The analgesic effects of morphine sulfate were compared to saline. Animals were tested for 3 days at each morphine dose level (2, 4, 8, and 16 mg/kg). Each 3-day morphine series alternated with 3 days of testing under saline. Significant differences were detected between saline and morphine at 4, 8, and 16 mg/kg.