Motion perception

Although the perception of emotion in individuals is an important social skill, very little is known about how emotion is determined from a crowd of individuals. We investigated the perception of emotion in scenes of crowds populated by dynamic characters each expressing an emotion. Facial expressions were masked in these characters and emotion was conveyed using body motion and posture only. We systematically varied the proportion of characters in each scene depicting one of two emotions and participants were required to categorise the overall emotion of the crowd. In Experiment 1, we found that the perception of emotions in a crowd is efficient even with relatively brief exposures of the crowd stimuli. Furthermore, the emotion of a crowd was generally determined by the relative proportions of characters conveying it, although we also found that some emotions dominated perception. In Experiment 2, we found that an increase in crowd size was not associated with a relative decrease in the efficiency with which the emotion was categorised. Our findings suggest that body motion is an important social cue in perceiving the emotion of crowds and have implications for our understanding of how we perceive social information from groups.

Different theories conceptualise dyslexia as either a phonological, attentional, auditory, magnocellular, or automatisation deficit. Such heterogeneity suggests the existence of yet unrecognised subtypes of dyslexics suffering from distinguishable deficits. The purpose of the study was to identify cognitive subtypes of dyslexia. Out of 642 children screened for reading ability 49 dyslexics and 48 controls were tested for phonological awareness, auditory discrimination, motion detection, visual attention, and rhythm imitation. A combined cluster and discriminant analysis approach revealed three clusters of dyslexics with different cognitive deficits. Compared to reading-unimpaired children cluster no. 1 had worse phonological awareness; cluster no. 2 had higher attentional costs; cluster no. 3 performed worse in the phonological, auditory, and magnocellular tasks. These results indicate that dyslexia may result from distinct cognitive impairments. As a consequence, prevention and rem...

The relationship between perception–action coupling and anticipatory skill in an interceptive task was examined using an in-situ temporal occlusion paradigm. Skilled and novice cricket batsmen were required to predict the direction of balls bowled towards them under four counterbalanced response conditions of increasing perception–action coupling: (i) verbal, (ii) lower-body movement only, (iii) full-body movement (no bat), and (iv) full-body movement with bat (i.e., the usual batting response). Skilled but not novice anticipation was found to improve as a function of coupling when responses were based on either no ball-flight, or early ball-flight information, with a response requiring even the lowest degree of body movement found to enhance anticipation when compared to a verbal prediction. Most importantly, a full-body movement using a bat elicited greater anticipation than an equivalent movement with no bat. This result highlights the important role that the requirement and/or opportunity to make bat–ball interception may play in eliciting skill differences for anticipation. Results verify the importance of using experimental conditions and task demands that closely reflect the natural performance environment in order to reveal the full nature of the expert advantage.

This experiment investigated the relationship between motivation, engagement, and learning in a video game task. Previous studies have shown increased autonomy during practice leads to superior retention of motor skills, but it is not clear why this benefit occurs. Some studies suggest this benefit arises from increased motivation during practice; others suggest the benefit arises from better information processing. Sixty novice participants were randomly assigned to a self-controlled group, who chose the progression of difficulty during practice, or to a yoked group, who experienced the same difficulty progression but did not have choice. At the end of practice, participants completed surveys measuring intrinsic motivation and engagement. One week later, participants returned for a series of retention tests at three different difficulty levels. RM-ANCOVA (controlling for pre-test) showed that the self-controlled group had improved retention compared to the yoked group, on average, ...

Laboratory-based studies of perceived speed show that, under most circumstances, perceived speed is reduced as a function of contrast. However, a recent investigation of perceived vehicular speed while driving around a closed road circuit showed no such effect (Owens, Wood, & Carberry, 2010, Perception, 39, 1199–1215). We sought to probe the source of this discrepancy, asking whether the presence or absence of stereoscopic motion information might account for the difference in results. In a two-alternative forced-choice psychophysical speed-discrimination task, observers compared the speed of high- and low-contrast driving clips filmed with a 3‑D camera and presented either stereoscopically (3‑D) or monoscopically (2‑D). Although perceived speed was reduced at low contrast, the size of this misperception was equivalent for 2‑D and 3‑D presentations. However, the inclusion of stereoscopic cues to vehicular speed caused significant improvements in the precision of speed judgments. It is concluded that although stereopsis can provide access to valuable information on perceived speed, contrast-independent speed estimation as demonstrated by Owens et al. (2010) is more likely to reflect the use of the full visual field in a real driving situation (compared with limited field of view simulations), or the additional contributions of nonvisual cues rather than stereopsis.

The visual acuity (VA) of patients with very low vision is classified using the semiquantitative scale "counting fingers" (CF), "hand motion" (HM), "light perception" (LP), and "no light perception." More quantitative measures would be desirable, especially for clinical studies. The results of clinical VA measurements, Early Treatment Diabetic Retinopathy Study (ETDRS) charts, and the Freiburg Visual Acuity Test (FrACT) were compared. The FrACT is a computerized visual acuity test that can present very large Landolt C optotypes when necessary. Examined were 100 eyes of 100 patients with various eye diseases (e.g., diabetic retinopathy, ARMD), covering a range of VAs from LP to decimal 0.32. The FrACT optotypes were presented on a 17-inch LCD monitor with random orientation. After extensive training, two ETDRS and FrACT measurements were obtained. The testing distance was 50 or 100 cm. ETDRS and FrACT coincided closely for VA > or = 0.02 (n ...

The colors, textures, and shapes of shadows are physically constrained in several ways in natural scenes. The visual system appears to ignore these constraints, however, and to accept many patterns as shadows even though they could not occur naturally. In the stimuli that we ...

The timing of events can influence spatial segmentation. Neighbouring regions flickering asynchronously at a high temporal frequency appear identical, but the visual system signals a 'phantom contour' between them. Using psychophysical procedures, we determined the spatial limitations of this form of temporal segmentation across the visual field. These limitations correspond closely to receptive field diameters of neurons in primary visual cortex (V1), and are also consistent with the spatial limitations of motion detection. Here, we propose a computational model in which the neural signal for phantom contours originates from individual neurons with receptive fields that are space-time separable, like those mapped in cat and macaque V1. Similar units are also employed in the first stages of models for the perception of local motion. The correspondence between theoretical models of temporal segmentation and motion perception in the human visual system, as well as psychophysical evidence that they have similar spatial limitations, support the notion that these processes are mediated by a common neural substrate situated in early in visual cortex.

. When the psychosis-- nonpsychosis grouping was considered, patients with psychosis responded dramatically better to ECT in all assessments, whereas those without psychosis responded similarly to both treatments. Conclusions: Overall ECT was a more potent treatment for patients with MDD, this being particularly evident in patients with MDD and psychosis; however, in patients with MDD without psychosis the effects of rTMS were similar to those of ECT. The results we report are encouraging and support an important role for rTMS in the treatment of severe MDD; however, additional blinded studies are needed to precisely define this role. Biol Psychiatry 2000;47:314--324 2000 Society of Biological Psychiatry Key Words: TMS, ECT, MDD, transcranial magnetic stimulation, electroconvulsive therapy Introduction T ranscranial magnetic stimulation (TMS) was introduced by Barker et al in 1985 as a new method for noninvas

The proximity principle is a fundamental fact of spatial vision. It has been a cornerstone of the Gestalt approach to perception, it is supported by overwhelming empirical evidence, and its utility has been proven in studies of the ecological statistics of optical stimulation. We show, however, that the principle does not generalize to dynamic scenes, ie, no spatiotemporal proximity principle governs the perception of motion. In other words, elements of a dynamic display separated by short spatiotemporal distances are not more ...

Sensory systems adapt to environmental change. It has been argued that adaptation should have the effect of optimizing sensitivity to the new environment. Here we consider a framework in which this premise is made concrete using an economic normative theory of visual motion perception. In this framework, visual systems adapt to the environment by reallocating their limited neural resources. The allocation is optimal when uncertainties about different aspects of stimulation are balanced. This theory makes predictions about visual sensitivity as a function of environmental statistics. Adaptive optimization of the visual system should be manifested as a change in sensitivity for an observer and for the underlying motion-sensitive neurons. We review evidence supporting these predictions and examine effects of adaptation on the neuronal representation of visual motion.

Transcranial alternating current stimulation (tACS) is used in clinical applications and basic neuroscience research. Although its behavioral effects are evident from prior reports, current understanding of the mechanisms that underlie these effects is limited. We used motion perception, a percept with relatively well known properties and underlying neural mechanisms to investigate tACS mechanisms. Healthy human volunteers showed a surprising improvement in motion sensitivity when visual stimuli were paired with 10 Hz tACS. In addition, tACS reduced the motion-after effect, and this reduction was correlated with the improvement in motion sensitivity. Electrical stimulation had no consistent effect when applied before presenting a visual stimulus or during recovery from motion adaptation. Together, these findings suggest that perceptual effects of tACS result from an attenuation of adaptation. Important consequences for the practical use of tACS follow from our work. First, because t...

In comparison to high level of knowledge of aircraft dynamics, the knowledge of a pilot in the human – aircraft system still appears to be insufficient. There have been a wide variety of studies and models describing the human’s behavior and perception, especially in the flight environment. However, only few of them concern the dynamics of spatial orientation perception. This article deals with one of the most important
aspects of aviation physiology. The aim of this paper is to consolidate information on the methods for modelling of the human perception of spatial orientation. This knowledge could be useful for further model’s development. Most of the models of the human perception of spatial orientation currently use one of three techniques for perception estimating: state observer, Kalman’s filter and Bayesian estimation. These models are able to mimic orientation perceptions, linear and circular vection, rotation and acceleration in the light, as well as estimate
vestibular-ocular reflex.