A counterchange mechanism for the perception of motion

A computational model for the perception of counterchange-specified motion is examined in detail and compared with various versions of the Reichardt motion detection model [Reichardt, W. (1961). Autocorrelation, a principle for the evaluation of sensory information by the central nervous system. In W. A. Rosenblith (Ed.), Sensory communication (pp. 303-317). New York: Wiley]. The counterchange model is composed of a pair of temporally biphasic subunits at two retinal locations, one detecting decreases and the other increases in input activation. Motion is signaled when both subunits are simultaneously excited, as determined by the multiplicative combination of their transient responses. In contrast with the Reichardt detector, which effectively tracks motion energy and accounts solely for results obtained with standard apparent motion stimuli (a surface is visible at one location, then at another), the counterchange model also accounts for the generalized apparent motion perceived between pairs of simultaneously visible surfaces. This indicates that standard apparent motion can be perceived via the same non-sequential, non-motion-energy mechanism as generalized apparent motion. There is no need for either an explicit delay mechanism to account for optimal motion perception at non-zero inter-stimulus intervals, or for inhibitory interaction between subunits to account for the absence of motion in the detector’s null direction (Barlow, H. B., & Levick, W. R., 1965). Both are emergent properties that result from the inhibitory states of the counterchange detector’s biphasic subunits. In addition to apparent motion, the counterchange principle potentially accounts for the perception of motion for drifting gratings, the short range motion perceived for random-dot cinematograms, and the motion perceived for continuously moving objects.     

The relation of cultural context and social relationships to career development in middle school

This study examined the role of supportive relationships (i.e., family, teacher, and peer) and agency (i.e., self-efficacy, motivation, and goal-setting orientation) on three outcomes: academic grades, distress, and career decidedness. Data from 588 middle school youth from Northern (N = 322) and Southern (N = 266) Italy were analyzed using path modeling. Results indicated that across gender and region, agency was consistently related to academic grades and career decidedness. However, the role of supportive relationships was found to differ across gender and region. For both boys from Northern Italy and girls from Southern Italy, the impact of family support on academic grades and career decidedness was mediated by agency. For girls from Northern Italy, family support related directly to academic grades and career decidedness. Implications for practice were described.     

The relationship between illness perceptions and panic in chronic obstructive pulmonary disease

BackgroundElevated levels of anxiety and panic are common in respiratory disease. To date the cognitive-behavioural model of panic has been utilised to help explain and manage panic in respiratory disease. This cross-sectional study investigated the relationship between illness perceptions and panic in chronic obstructive pulmonary disease (COPD) within a self-regulatory framework of adaptation to physical illness.MethodsFifty-nine participants with COPD completed questionnaires measuring illness perceptions, anxiety and depression, frequency and severity of panic attacks and impact of disease on daily life and well-being. The percent forced expiratory volume in the first second (FEV₁%) was used as an objective measure of lung function.ResultsHigh levels of clinical anxiety and depression were reported (35% and 19% respectively). Sixty-three percent of participants reported experiencing a panic attack during the previous year and of these 51% during the previous month. Panic was unrelated to level of disease severity. Specific illness perceptions (beliefs relating to illness identity, timeline, consequences and emotional representations) were important in differentiating between panickers and non-panickers.ConclusionsThe results highlight the importance of assessing illness perceptions within the framework of the self-regulatory model to provide an additional theoretical perspective for investigating and managing panic in chronic respiratory disease.     

Does Self-Reported Posttraumatic Growth Reflect Genuine Positive Change?

ABSTRACT— In this study, we evaluated the validity of self-reported posttraumatic growth (PTG) by assessing the relation between perceived growth and actual growth from pre- to posttrauma. Undergraduate students completed measures tapping typical PTG domains at Time 1 and Time 2 (2 months later). We compared change in those measures with scores on the Posttraumatic Growth Inventory (PTGI; Tedeschi & Calhoun, 1996 ) for those participants who reported a traumatic event between Time 1 and Time 2 ( n = 122). PTGI scores generally were unrelated to actual growth in PTG-related domains. Moreover, perceived growth was associated with increased distress from pre- to posttrauma, whereas actual growth was related to decreased distress, a pattern suggesting that perceived and actual growth reflect different processes. Finally, perceived (but not actual) growth was related to positive reinterpretation coping. Thus, the PTGI, and perhaps other retrospective measures, does not appear to measure actual pre- to posttrauma change.