Do Students with Different Characteristics Take Part in Psychology Experiments at Different Times of the Semester?

ABSTRACT In this study we examined 15 personality and demographic differences between psychology students who took part in experiments at different times of the semester and different times of the day. In general, few significant relations were found and those that did emerge were small in magnitude. Females and freshmen signed up for experiments earlier in the semester. Females took part in their first experiment earlier in the semester, as did students who were Protestant and who came from smaller home towns. Students low in self-consciousness also tended to begin participating earlier. Extraverts participated earlier in the day than introverts. Results generally were consistent with previous findings of differences between research volunteers and non-volunteers. However, it was concluded that because of their small magnitude and inconsistency from site to site, with a few precautions experimenters probably need not be concerned that timing effects threaten the external validity of psychological research outcomes.     

Confidence intervals for the MMPI-2

The confidence intervals for the Minnesota Multiphasic Personality Inventory (MMPI-2) clinical scales were investigated. Based on the clinical scale reliabilities published in the MMPI-2 manual, estimated true scores, standard errors of measurement for estimated true scores, and 95% confidence intervals centered around estimated true scores were calculated at 5-point MMPI-2 T-score intervals. The relationships between obtained T-scores, estimated true T-scores, scale reliabilities, and confidence intervals are discussed. The possible role of error measurement in defining scale high point and code types is noted.     

The MCMI-II depression scales: do they assist in the differential prediction of depressive disorders?

This study examined the diagnostic efficiency of the Millon Clinical Multiaxial Inventory-II (MCMI-II) Major Depression (CC) and Dysthymia (D) scales for the differential prediction of unipolar depressive disorders. The MCMI-II was administered to 109 inpatients at a large private psychiatric hospital in the Midwest. All patients had a primary Axis I diagnosis of a depressive disorder, given at discharge by the attending psychiatrists. When CC scores were compared to clinician diagnoses, results indicated that the sensitivity of the CC scale was improved over what had previously been reported for studies involving the MCMI-I CC scale. However, overall, the D scale functioned slightly better as a predictor of major depression than did the CC scale. One likely factor in explaining this finding is that the CC scale contains very few items assessing vegetative/somatic symptomatology, which are the critical factors in distinguishing major depression from other unipolar depressive disorders.     

Visible persistence following a brief increment in stimulus luminance

In previous studies, it has been demonstrated that visible persistence--the period for which the perceived duration of a stimulus exceeds its physical duration--can be extended by briefly incrementing the luminance of the stimulus immediately prior to offset. Using a two-component pattern integration task, we show that this effect is not an artifact of change in the total luminous flux within the stimulus. Visible persistence was unaffected by overall luminance of the stimulus. It was also time-locked to the luminance increment. Visible persistence is seen to result from a process that is initiated by stimulus onset and that can be either wholly or partially reinitiated by the onset of the luminance increment. The duration of this process (which determines the duration of stimulus visibility) can be modified in a graded fashion by stimulus events that occur after its initiation. We outline a single-process inhibitory feedback model of the persistence mechanism that accounts for the present findings.     

Correlation for scores on Revised Test of Visual-Motor Integration and Copying Test in a South African sample

A statistically significant correlation of 0.618 was obtained between scores from 62 preschool children on the Revised Developmental Test of Visual-Motor Integration and the Copying Test. Merely 38% of Copying Test variance was associated with changes in Test of Visual-Motor Integration variance, so in practice these tests should not be substituted for one another.     

Manual reaction times and error rates in stutterers.

In this study 18 stutterers and 18 nonstutterers were presented trials on which they should press a button as fast as possible, intermixed with trials which required no responding. Stutterers had slightly faster reaction times but also made slightly more errors, that is, they tended to press the button when they should not have done so. As neither difference was significant, it was concluded that stutterers did not differ from normal speakers in manual reaction speed, nor did they choose a different speed-accuracy trade-off criterion for the given task.     

The Fraser illusion: complex figures

The cause of the Fraser illusion, which occurs when a line made up of tilted segments itself appears tilted, is examined further. In this series of experiments, we used figures that resembled the original Fraser illusion; they were more complex than those reported on in our previous paper (Stuart & Day, 1988). The figures were used to explore two theories of the Fraser illusion further: that it is the result of interactions between orientation selective units, and that it is a consequence of the local, distributed processing of orientation. The presence of background elements like those used in the original illusion led to an increase in the strength of the illusion, but the shape of these elements had no differential effect on illusion strength. There was a differential effect of the background on the assimilative and contrast illusions, owing respectively to small and large tilts of the inducing elements. The illusion was markedly reduced at small visual angles when the background was absent, but it was only slightly affected when the background was present. All these findings are difficult to explain in terms of interactions between single units, either at the same or at different scales in the image. The effects of luminance contrast and isoluminance on the illusion were not consistent with either theory, but they indicated that researchers need to consider the role of figure-ground organization in this illusion.     

Human Aggressive and Escape Responding: Effects of Provocation Frequency

The Psychological Record - The effect of point loss frequency on aggressive and escape responding was investigated in two experiments. Subjects could respond on levers marked “A,”...