Visual discrimination thresholds for time to arrival

In a seminal article, Todd (Journal of Experimental Psychology: Human Perception and Performance 7:795-810, 1981) reported a difference threshold of about 50 ms to discriminate the times of arrival of two differently sized objects that simultaneously approached head-on at constant but different velocities. Subsequent investigators, however, have often found much higher thresholds. We did one complete replication of Todd’s experiment, and then modified his stimuli and experimental regime, which we hypothesized may have been responsible for some of the discrepancies reported in the literature. Unlike Todd and most other researchers, we exclusively used untrained observers. Several of our participants performed almost as well as the trained observers used by Todd and others, but the performance of most of our participants fell short of this standard. Furthermore, thresholds were affected by the experimental regimes, with large differences between objects’ sizes and speeds compromising performance. Analyses of the response patterns revealed that the responses were driven mainly by the objects’ relative apparent sizes.     

Time-to-passage judgments in nonconstant optical flow fields

The time until an approaching object will pass an observer (time to passage, or TTP) is optically specified by a global flow field even in the absence of local expansion or size cues. Kaiser and Mowafy (1993) have demonstrated that observers are in fact sensitive to this global flow information. The present studies investigate two factors that are usually ignored in work related to TTP: (1) non-constant motion functions and (2) concomitant eye rotation. Non-constant velocities violate an assumption of some TTP derivations, and eye rotations may complicate heading extraction. Such factors have practical significance, for example, in the case of a pilot accelerating an aircraft or executing a roll. In our studies, a flow field of constant-sized stars was presented monocularly on a large screen. TTP judgments had to be made on the basis of one target star. The flow field varied in its acceleration pattern and its roll component. Observers did not appear to utilize acceleration information. In particular, TTPs with decelerating motion were consistently underestimated. TTP judgments were fairly robust with respect to roll, even when roll axis and track vector were decoupled. However, substantial decoupling between heading and track vector led to a decrement in performance, in both the presence and the absence of roll.     

Motivational interviewing in health promotion: it sounds like something is changing.

Motivational interviewing (MI), initially developed for addiction counseling, has increasingly been applied in public health, medical, and health promotion settings. This article provides an overview of MI, outlining its philosophic orientation and essential strategies. Major outcome studies are reviewed, nuances associated with the use of MI in health promotion and chronic disease prevention are described, and future directions are offered.     

The Relationship Between Peer Status and Depressive Symptoms in Children and Adolescents

The purpose of this study was to examine the relationship between specific symptoms of depression and particular styles of peer difficulties. Participants were 1687 students in fourth, sixth, seventh, eighth, ninth, and eleventh grades from a midsized Midwestern city. Based on previous studies, it was hypothesized that rejected and neglected youths would report greater depressive symptomatology than other peers. In addition, aggressive-rejected youth were predicted to report more Interpersonal Problems while submissive-rejected youths were expected to report more Anhedonia. There were no sociometric group differences on global scores of depression as measured by the Children's Depression Inventory; however, the aggressive- and submissive-rejected youths did report specific differences. Aggressive-rejected youths reported more Interpersonal Problems and feelings of Ineffectiveness, while the neglected and submissive-rejected youths reported more Anhedonia. Taken together, such differences provide support for differentiating among types of rejected students and suggest that different interventions may be necessary to address the needs of these youths.     

Seven-minute rhythms in stable avoidance conditioning

Investigation of the “inextinguishable” locomotor avoidance reflex revealed periodic oscillating of reaction times, motor reaction times, and latent periods, when the conditional stimuli were applied every half minute. These rhythmic properties were verified by autocorrelation. Frequency distribution of all significant wavelengths occurring in rhythmic processes of stabilized conditioning showed seven-minute wavelengths for the most part and smaller numbers of wavelengths of 5 to 9 and 14 minutes. A significant number of wavelengths of 3.5 minutes was not seen. Locomotor avoidance conditioning permitted separate automatic registration of reaction times and motor reaction times. The two values showed synchronous periodic courses in stabilized conditioning, with the motor reaction times being longer. The periodicities found, thought to be due to controlling processes in the central nervous system, can be explained in either or both of two ways: the periodic courses represent a frequency range of a structured time mechanism in the sense of a “clock inherent in an organism”; the rhythms of conditional processes represent an adaptation mechanism in organism-environment interrelations. It can be assumed that the two mechnanisms work synergistically.     

Counting on working memory in simple arithmetic when counting is used for problem solving

A concurrent-task methodology was used to investigate relations between the availability of aspects of working memory resources and both strategy selection and execution while simple addition equations (e.g., 4 + 3 = 8) were being verified. Consistent with prior research in which production trials have been used, undergraduates selected a variety of procedures other than retrieval. Availability of working memory resources did not generally affect strategy selection. Disrupting central executive and phonological aspects of memory affected strategy execution, but only when min counting was used to solve the problems. These and other features of the results suggest that availability of working memory resources does not contribute to individual differences in strategy selection and time to execute retrieval processes.     

An inter-hemispheric imbalance in the psychopath’s brain

Psychopathy is associated with two extremities. On the one hand, psychopathic individuals lack any concern for social norms and they are severely poor in maintaining healthy social relationships. In addition, the ability of individuals with psychopathy to feel certain emotions such as empathy, guilt or fear is seriously compromised. In contrast to these deficits, some behaviors and tendencies are exaggerated in psychopathy. For instance, psychopathic individuals display higher than normal impulsivity, stimulation-seeking, aggression and risk-taking. There are indications in the literature that pro-social behavior, as well as the feelings of empathy, guilt and fear are mediated predominantly by regions within the right hemisphere (RH), whereas impulsivity, stimulation-seeking, aggression and risk-taking are linked primarily with left hemisphere (LH) activity. From a neurobiological perspective, it seems that psychopathy may be associated with an altered and imbalanced inter-hemispheric dynamics; a relatively hyperfunctioning LH and/or a hypofunctioning RH. Furthermore, within the psychopathic population, the RH hypofunctioning is more characteristic of primary psychopathy with its affective and interpersonal deficits, while the LH hyperfunctioning is most typical of the secondary psychopathy which is marked by impulsivity and antisocial style.     

Dissociation of acquisition and expression of fear conditioned responses under working memory load

Previously, it has been suggested that high working memory load (WML) prevents associative learning and, thus, conditioned responses (CRs) during differential-delay fear conditioning. However, previous studies did not distinguish between the effects of WML on the acquisition versus the expression of the CRs. In the present study, we reinvestigated this issue by manipulating WML during either acquisition or postconditioning and showed that the absence of a differential CR under high WML does not indicate the absence of the acquisition of this CR. Thus, a significant CR was observed during a task-free postconditioning phase, and there was no CR during the preceding acquisition phase with high WML. Conversely, a normally acquired CR was impaired by high WML during the postconditioning phase. The results suggest that high WML affects the expression of the CR. If they are not experimentally separated, the effects of WML on the acquisition and expression of the CR may occur together, and the findings may be erroneously interpreted as indicating a lack of associative learning.     

Temporal-range estimation of multiple objects: evidence for an early bottleneck

When making parallel time-to-contact (TTC) estimates of two approaching objects, the two respective TTC estimates interfere with one another in an asymmetric fashion. The TTC of the later-arriving object is systematically overestimated, while the estimated TTC for the first-arriving object is as accurate as in a condition presenting only a single object. This asymmetric interference points to a processing bottleneck that could be due to early (e.g., during the estimation of the TTC from the optic flow) or late (e.g., during the timing of the response or the motor execution) constraints in the TTC estimation process. We used a Sperling-like prediction-motion task to differentiate between these two possibilities. Participants produced an absolute estimate of the TTC of only one of two objects approaching a target line. The target object to which the response was to be made was indicated by an auditory cue that occurred either at motion-onset or at the instant at which the two objects disappeared from the screen (occlusion-onset). The cue at motion-onset should disengage visual processing of the irrelevant stimulus. The cue at occlusion-onset, in contrast, requires visual processing of both relevant and irrelevant stimulus until occlusion. A single-object condition was introduced as a control condition. Results show symmetric interference in the motion-onset condition. In the occlusion-onset condition however, the results were congruent with asymmetric interference. Thus, the processing bottleneck in TTC estimation is originating at the earlier stages.     

Slope estimation and viewing distance of the observer

The overestimation of geographical slant is one of the most sizable visual illusions. However, in some cases estimates of close-by slopes within the range of the observer’s personal space have been found to be rather accurate. We propose that the seemingly diverse findings can be reconciled when taking the viewing distance of the observer into account. The latter involves the distance of the observer from the slope (personal space, action space, and vista space) and also the eye-point relative to the slope. We separated these factors and compared outdoor judgments to those collected with a three-dimensional (3D) model of natural terrain, which was within arm’s reach of the observer. Slope was overestimated in the outdoors at viewing distances between 2 m and 138 m. The 3D model reproduced the errors in monocular viewing; however, performance was accurate with stereoscopic viewing. We conclude that accurate slant perception breaks down as soon as the situation exits personal space, be it physically or be it by closing one eye.