Image statistics and the perception of apparent motion

The short- and long-range apparent motion processes are discussed in terms of the statistical properties of images. It is argued that the short-range process, exemplified by the random-dot kinematogram, is primarily sensitive to the dipole statistics, whereas the long-range process, exemplified by illusory occlusion, is treated by the visual system primarily in terms of the tripole and higher statistical correlation functions. The studies incorporate the balanced dot, which is a unique stimulus element that permits high pass filtering while preserving detailed positional information. Low spatial frequencies are shown to be critical for texture segregation in random-dot kinematograms, independent of the grain size or number density of texture elements. Illusory path perception in the long-range process is shown not to require low spatial frequencies, but is sensitive rather to global temporal phase coherency. These results are interpreted in terms of the respective roles of the power and phase spectra in perceptual organization. The construction of balanced dots is discussed in detail.     

Stimulus repetition effects and the dimension-feature distinction in alternative targets

The negative repetition effect (NRE) refers to a poorer perception of the target in noise-same-as-target than in noise-alternative-target displays. Using the parenthesis as target and noise that are either identical or different in orientation, we tested predictions derived from a feature-specific inhibition model (Bjork & Murray, 1977) that explains the NRE as arising from inhibitory interactions among channels handling identical inputs. Contrary to our expectation of evidence for orientation-specific inhibition, a positive repetition effect (PRE) was observed. We also found a PRE for the dimension target sets whose stimuli differ only in orientation and an NRE for the feature target sets whose stimuli differ in the number of elements. Further experiments that systematically varied relationships between alternative targets indicate that these basic findings, termed the stimulus attributes effects, do not arise from pattern masking, perceptual strategies, or response bias.     

Transparent layer constancy

Perceived transparency was studied as a constancy problem. In the episcotister (E-) model of scission, luminances are partitioned into layer and background components; four luminances determine values of two layer parameters that specify constancy of a transparent layer on different backgrounds. The E-model was tested in an experiment in which 12 Ss matched 24 pairs of four-luminance patterns by adjusting two luminances of the comparison pattern. Both the standard and the comparison were perceived as a transparent layer on a checkerboard. The E-model predicts matches when layer values are identical in the two patterns. One parameter was constant, constraining the adjustment along the second dimension. Obtained values corresponded well with E-predictions. Alternative models based on local luminance or average contrast ratios accounted for less variability. Results indicate that transparency models should utilize luminance, not reflectance, as the independent variable.     

On the relation between metacontrast masking and suppression of visible persistence

Does the introduction of additional contours in a display sequence (an operation known to reduce the strength of suppression in metacontrast) also reduce suppression of visible persistence? In three experiments, duration of visible persistence was estimated by a method in which successful performance depends on the temporal integration of a pattern whose elements are displayed in two successive frames. In this procedure, the arrival of the trailing frame is known to exert a suppressive influence on the visible persistence of the leading frame. Embedding the elements of the leading frame within additional contours (a line grid) reduced the degree of suppression exerted by the trailing frame. This did not occur when the grid was part of the trailing display. We conclude that suppression of visible persistence and metacontrast masking belong to the same class of events.     

A kinematic analysis of anticipatory coarticulation in the speech of anterior aphasic subjects using electromagnetic articulography

An investigation was made into the extent and time course of anticipatory coarticulation in the speech of two normal and two anterior aphasic, German-speaking subjects. Both labial and velar coarticulation gestures were investigated. Subjects produced sentences containing target words contrasting in postconsonantal vowel rounding (e.g., [geli:ge]/[gely:gel]) and in nasality (e.g., [ti:de]/[ti:ne]). Speech kinematics were monitored by means of electromagnetic articulography. The data revealed that for correct productions, aphasic speakers' coarticulatory patterns were more highly variable than those of control subjects. These differences, however, were found chiefly for spatial displacement characteristics, while the temporal aspects of articulator movement necessary for anticipatory coarticulation appeared largely intact. Articulator mistiming did not appear to explain a small corpus of stop/nasal substitution errors produced by one of the aphasic speakers.     

Benzodiazepine receptor ligand influences on acquisition: suggestion of an endogenous modulatory mechanism mediated by benzodiazepine receptors

In rats, pretraining ip administration of the central benzodiazepine receptor antagonist, flumazenil (5.0 mg/kg), or of the inverse agonist, n-butyl-beta-carboline-3-carboxylate (BCCB) (0.2 or 0.5 mg/kg), facilitated retention of a step-down inhibitory avoidance task; the central agonists, clonazepam and diazepam (0.4 or 1.0 mg/kg), had an opposite effect, and the peripheral agonist, 4'-chlordiazepam (1.25 or 6.25 mg/kg), was without effect. Pre- but not post-training flumazenil (2.0 mg/kg) blocked the effect of BCCB (0.5 mg/kg), clonazepam (1.0 mg/kg), or diazepam (1.0 mg/kg) given also pretraining. The post-training administration of all of these drugs had no effect on retention of the avoidance task. Flumazenil (5.0 mg/kg) and BCCB (0.5 mg/kg), given before training, enhanced retention test performance of habituation to a buzzer but not of habituation to an open field. In the three tasks studied, none of the drugs used had any appreciable effect on training session parameters. These results suggest that there is an endogenous mechanism mediated by benzodiazepine agonists, sensitive to inverse agonists, that normally down-regulates acquisition of certain behaviors; this mechanism becomes activated only when the tasks involve or occur with a certain degree of stress or anxiety (i.e., inhibitory avoidance or habituation to the buzzer) and not in less stressful or anxiogenic tasks (i.e., habituation to an open field).     

Glucose and physostigmine effects on morphine- and amphetamine-induced increases in locomotor activity in mice

Recent findings indicate that glucose antagonizes several behavioral effects of cholinergic antagonists and augments those of cholinergic agonists. For example, scopolamine elicits increased locomotor activity, an action which is attenuated by glucose and by combined treatment with glucose and physostigmine at doses which are individually without effect. Opiate and catecholamine agonists, such as morphine and amphetamine, also elicit hyperactivity. The present study examined interactions of glucose and physostigmine with morphine- and amphetamine-induced hyperactivity. Mice received saline, morphine (10 mg/kg), or amphetamine (1 mg/kg) 50 min prior to testing, followed by saline, physostigmine (0.01, 0.05, 0.1, or 0.2 mg/kg), or glucose (10, 50, 100, or 500 mg/kg) administered 20 min prior to activity testing in an open field. Physostigmine significantly attenuated both morphine- and amphetamine-induced increases in activity, but higher doses were required to attenuate the effects of amphetamine. Like physostigmine, glucose significantly attenuated morphine-induced activity levels, but unlike physostigmine, glucose did not attenuate amphetamine-induced activity. Thus, the behavioral effects of morphine were more susceptible to modification by physostigmine and glucose than were the effects of amphetamine. The attenuation of morphine-induced hyperactivity demonstrates a similarity between glucose and cholinergic agonists, and also indicates that glucose may inhibit, directly or indirectly, opiate functions. More generally, these findings add to the evidence that circulating glucose levels selectively influence a growing list of behavioral and neurobiological functions.     

Counselor Responsiveness to Client Religiousness

An understanding of the degree and Quality of client religiousness and the connections between client issues and religion can enhance counselor resposiveness to the potentially religious dimension of client issues.     

PASTORAL PSYCHOTHERAPY: IS IT UNIQUE?

Proponents and practitioners of pastoral psychotherapy hold to the idea that it is a unique form of psychotherapy. Little empirical or procedural evidence seems to exist to substantiate that viewpoint. Indeed, the data suggest that pastoral psychotherapy is a close kin to secular psychotherapy, not only in practice, but in the opinion of those who seek it out for help. This article takes the viewpoint that pastoral psychotherapy should be unique and attempts to show how it can be. The author stresses that it is ordination that makes pastoral psychotherapy unique, because the ordained pastor is both a theologian and a representative of the church. These two elements provide unique “lenses” for doing psychotherapy. To the extent that these lenses are not being used, the author issues a challenge to pastoral psychotherapists to bring this uniqueness to the forefront.     

Detectability as a function of target location: effects of spatial configuration

Marked differences in detectability as a function of spatial location, a "detectability gradient," are observed when subjects are required to detect a briefly exposed target pattern of uncertain location in the presence of a number of nontarget patterns. Target detectability also is inversely related to the number of nontarget patterns which are present in this search paradigm. These previous findings provide strong evidence for a serial process in which increasing probability of error occurs during a scan of a rapidly degrading neural representation of the visual image following a brief exposure to the stimuli. It is not yet established whether this scan is attentional or perceptual in nature. The present experiments test the hypothesis of an attentional scan by presenting the target and nontarget patterns in spatially segregated groups. If the scan is attentional, then target detectability under these circumstances would be expected to exhibit the characteristic phenomenon of "group processing"--a close clustering of detection performance for targets located within a group and large differences in detectability across groups. As no evidence for group processing was observed, the results fail to support the view that the scan is attentional in nature but are fully consistent with a nonattentional scan.