Examination of apparent extent as an explanation of the Poggendorff effect

The explanation of apparent misalignment in the Poggendorff figure, based on underestimation of the intertransversal distance, was investigated in two experiments. In Experiment 1, subjects judged the intertransversal distance in the traditional Poggendorff figure and two of its variants. The size of the acute angle and the intertransversal distance were manipulated. Half of the subjects made the judgments with the method used by Wilson and Pressey (1976) and the other half made their judgments with the method used by Greist-Bousquet and Schiffman (1981). The results indicated that perceived intertransversal distance was greater with the former method. In Experiment 2, subjects adjusted the transversals to apparent collinearity in the same displays as were used in Experiment 1. The collinearity judgments were transformed to allow comparison with the results of Experiment 1. Comparison of the collinearity judgments with the distance judgments indicated that they did not follow similar trends. For each Poggendorff variant, proportional distance judgments increased as the size of the acute angle increased, and decreased as the intertransversal distance increased. Collinearity judgments did not vary as a function of intertransversal distance. As the size of the acute angle increased, collinearity judgments increased for two of the Poggendorff variants but decreased for the third. It was concluded that the findings did not support the explanation of apparent misalignment based on underestimation of the intertransversal distance.     

Counseling: A conversion experience

In this article, the experience of conversion, which is usually delegated to the realm of spiritual studies, is applied to the counseling experience. It is posited that a person who goes through a successful counseling process will experience a turning around, will cease leading life in a dysfunctional way, and will move forward in a manner by which the person experiences life in a new perspective. This new perspective brings the person wholeness and balance.     

Carl Rogers and Martin Luther—A “reformation” in the helping professions

The 16th century schism in Christian thought leading to the Reformation has an interesting analogy in Carl Rogers' attempt to reform the helping professions. An exploration of this analogy clarifies much of the theoretical tension in the contemporary arena of pastoral counseling.     

Changes in the incidence of nocturnal bruxism in college students: 1966-1989

The frequency of self-reported nocturnal bruxism in three large samples of college undergraduates was compared as a means of assessing change in the incidence of this disorder since 1966. We found the incidence of nocturnal bruxism had increased from 5.1% to 20.5% in college students over the period covered by these studies.     

H-reflexes during a motor skill acquisition task

H-reflex amplitudes were studied during the acquisition of a motor skill involving coordinated isometric plantarflexion at the ankle joints as subjects learned to trace a triangular pattern on an oscilloscope screen by controlling plantarflexion torque applied against load cells. Torque feedback was presented on a subject oscilloscope with the right foot controlling a vertical cursor and the left foot a horizontal cursor. Eleven subjects reached criterion performance. H-reflexes were recorded from the right soleus and timed to the initiation of soleus muscle activity to plantarflex the foot. Average time to complete one trial decreased from 9 sec. in the prelearning block to 4 sec. postlearning. No single learning strategy was evident as subjects varied widely in their levels of H-reflex amplitude, but during postlearning, H-reflex amplitude became consistent within subjects as tracing performance became faster and accurate.     

Pitch motion with random chord sequences

Perception of global pitch motion was studied through psychoacoustic experiments with random chord sequences. Chords contained either six or eight (fixed) tone elements, being sinusoidal, sawtooth-like, or Shepard tones, which were either on or off according to a probability controlled by the experimenter. Sequences of 2, 4, 5, or 8 chords were used. Identification by subjects of the perceived direction of overall pitch motion (up or down) was found to be well accounted for by a model in which the ultimate pitch motion percept is given by a sum of contributions from selected element transitions--that is, transitions between adjoining tone elements in successive time frames only. In its simplest form, this dipole contribution model has only one free parameter, the perceptual noise for an element transition, which was estimated for various acoustic tone representations and chord arrangements. Results of two experiments, which were carried out independently in two different laboratories, are reported.     

Magnitude estimates for electrical pulses: evidence for two neural mechanisms

The hypothesis that there are two neural mechanisms for electrocutaneous stimulation--one that is sensitive to low current and is adaptive to repeated stimulation and another that is responsive to high current and is less adaptive--was tested in a control and four main experiments. In the main experiments, magnitude estimates obtained for single electrical pulses (of 2-msec duration) were described by a simple power function for each combination of high- and low-current levels and 10 trial blocks. The results were: (1) The slope of the power function for low current was steeper than was that for high current; (2) for low current, the intercept of the power function decreased with increasing block, whereas for high current, it remained constant over blocks; (3) this decrease of the intercept for low current disappeared when judgmental blocks were separated by a rest period of 8 min; (4) the modulus did not affect the slope; (5) for a large modulus combined with low current, the intercept decreased rapidly over trial blocks, whereas for a small modulus combined with high current, the intercept increased over trial blocks. The first four findings support the two-mechanism hypothesis, but the last one may also be interpretable in terms of the regression to absolute scale values.     

The effects of auditory streaming on duplex perception

When a formant transition and the remainder of a syllable are presented to subjects' opposite ears, most subjects perceive two simultaneous sounds: a syllable and a nonspeech chirp. It has been demonstrated that, when the remainder of the syllable (base) is kept unchanged, the identity of the perceived syllable will depend on the kind of transition presented at the opposite ear. This phenomenon, called duplex perception, has been interpreted as the result of the independent operation of two perceptual systems or modes, the phonetic and the auditory mode. In the present experiments, listeners were required to identify and discriminate such duplex syllables. In some conditions, the isolated transition was embedded in a temporal sequence of capturing transitions sent to the same ear. This streaming procedure significantly weakened the contribution of the transition to the perceived phonetic identity of the syllable. It is likely that the sequential integration of the isolated transition into a sequence of capturing transitions affected its fusion with the contralateral base. This finding contrasts with the idea that the auditory and phonetic processes are operating independently of each other. The capturing effect seems to be more consistent with the hypothesis that duplex perception occurs in the presence of conflicting cues for the segregation and the integration of the isolated transition with the base.     

Texture perception in sighted and blind observers

The purpose of the present study was to evaluate the utility of visual imagery for texture perception. In Experiment 1, sighted, early-blind, and late-blind observers made relative smoothness judgments of abrasive surfaces using active or passive tough. In Experiment 2, subjects compared vision and touch in the accuracy of smoothness detection, using a broad range of textures, including very fine surfaces. No differences appeared between the sighted and the blind, and it did not matter if touch were active or passive. Vision and touch showed similar performance with relatively coarse textures, but touch was superior to vision for much finer surface textures. The results were consistent with the notion that visual coding of tactual stimuli is not advantageous (or necessary) for texture perception, since touch may hold advantages for the detection of the smoothness of surfaces.     

Illusion decrement and transfer of illusion decrement in real- and subjective-contour Poggendorff figures

The reduction in illusion magnitude with visual inspection and the transfer of such illusion decrement to a noninspected figure were examined in real- and subjective-contour Poggendorff figures. For both types of figures, illusion magnitude decreased significantly, and in a similar manner, during a 5-min inspection period. Postinspection tests showed that inspecting either a real- or subjective-contour figure resulted in a reduction in illusion magnitude for the other, noninspected figure. These findings suggest that real- and subjective-contour Poggendorff figures share a similar global organization and are thus probably processed in a similar manner. These characteristics make subjective-contour figures a useful tool for separating illusion-producing mechanisms into structural and strategy components.