Impulsivity, self-regulation, and response withholding in university-student drinkers

This study was designed to determine how impulsivity, self-regulation, and response withholding are related to one another and to university students' drinking behavior. Participants (N = 108) completed measures of impulsivity, self-regulation, and alcohol consumption. In addition, a computerized Go/No Go task and a backward memory task were used to measure participants' behavioral impulsivity and their memory capacity. The aim was to determine whether (a) light/moderate and heavy drinkers would respond differently when the task stimuli were alcohol-related compared to when they were alcohol-unrelated and (b) whether the accuracy of participants' responses was related to their cognitive ability. Compared to light/moderate drinkers, heavy drinkers were low in self-regulation and high in impulsivity. Heavy drinkers and those with lower memory capacity were also poorer at withholding responses on No Go trials. These findings point to personality/cognitive characteristics that influence university students' alcohol consumption.

Hostility Is Associated with Self-Reported Cognitive and Social Benefits Across Massively Multiplayer Online Role-Playing Game Player Roles

Massively Multiplayer Online Role-Playing Games (MMORPGs) can sometimes be associated with patterns of play that are harmful to health and well-being. Hazardous MMORPG play has been linked to hostility (toward other people). However, little is known about how hostility, as a risk factor, relates to players' choices within games, or players' experiences of the positive aspects of MMORPGs. In this study, we surveyed 5,847 players of Jagex's RuneScape to examine how trait hostility relates to player roles that prioritize skill acquisition/improvement (Skillers), combat (Killers), or narrative challenges (Questers). Killers reported modestly higher levels of trait hostility than Skillers and Questers. The most hostile players reported the strongest importance of in-game relative to offline achievements, possibly indicating hazardous involvement. Critically, hostile players also report the strongest cognitive and social benefits. These include (i) skills acquired through MMORPGs that help players to achieve things in their offline lives and (ii) online relationships that benefit offline relationships. These findings offer a new perspective on the way that a previously reported risk factor for harmful MMORPG play relates to player engagement, possibly by offering a helpful space for hostile individuals to develop problem solving and social skills. This suggests that some individuals who might be vulnerable to developing harmful patterns of MMORPG play may simultaneously experience greater tangible benefits.

Brands and Inhibition: A Go/No-Go Task Reveals the Power of Brand Influence

Whether selecting a candy in a shop or picking a digital camera online, there are usually many options from which consumers may choose. With such abundance, consumers must use a variety of cognitive, emotional, and heuristic means to filter out and inhibit some of their responses. Here we use brand logos within a Go/No-Go task to probe inhibitory control during the presentation of familiar and unfamiliar logos. The results showed no differences in response times or in commission errors (CE) between familiar and unfamiliar logos. However, participants demonstrated a generally more cautious attitude of responding to the familiar brands: they were significantly slower and less accurate at responding to these brands in the Go trials. These findings suggest that inhibitory control can be exercised quite effectively for familiar brands, but that when such inhibition fails, the potent appetitive nature of brands is revealed.

Attention and the subjective expansion of time

During brief, dangerous events, such as car accidents and robberies, many people report that events seem to pass in slow motion, as if time had slowed down. We have measured a similar, although less dramatic, effect in response to unexpected, nonthreatening events. We attribute the subjective expansion of time to the engagement of attention and its influence on the amount of perceptual information processed. We term the effect time's subjective expansion (TSE) and examine here the objective temporal dynamics of these distortions. When a series of stimuli are shown in succession, the low-probability oddball stimulus in the series tends to last subjectively longer than the high-probability stimulus even when they last the same objective duration. In particular, (1) there is a latency of at least 120 msec between stimulus onset and the onset of TSE, which may be preceded by subjective temporal contraction; (2) there is a peak in TSE at which subjective time is particularly distorted at a latency of 225 msec after stimulus onset; and (3) the temporal dynamics of TSE are approximately the same in the visual and the auditory domains. Two control experiments (in which the methods of magnitude estimation and stimulus reproduction were used) replicated the temporal dynamics of TSE revealed by the method of constant stimuli, although the initial peak was not apparent with these methods. In addition, a third, control experiment (in which the method of single stimuli was used) showed that TSE in the visual domain can occur because of semantic novelty, rather than image novelty per se. Overall, the results support the view that attentional orienting underlies distortions in perceived duration.

Effect of aging on visual shape distortion

BACKGROUND

Individuals experience a visual illusion created by shape interaction: when two shapes are presented successively and briefly, the form of the second (test) shape appears distorted due to the form of the first (prime) shape; this shape interaction is called the shape distortion effect. While age-related deterioration in performance is found in various aspects of visual perception, the effect of aging on the shape distortion effect has not been evaluated.

OBJECTIVE

The purpose of this study is to determine the effect of aging on the shape distortion effect.

METHODS

We measured the perception of briefly presented elementary shapes and of the shape distortion effect in 29 healthy volunteers, with ages ranging from 18 to 83 years. For each shape interaction trial, a prime rectangle was presented (vertical or horizontal) for 45 ms, followed by an interstimulus interval for 135 ms, a test circle for 60 ms and finally a random dot mask for 300 ms. The test circle was presented in each quadrant of the visual field. The prime rectangle was flashed either at the same position as the test circle (0 degrees offset, intrahemifield) or 11 degrees apart, displaced horizontally in the opposite hemifield (11 degrees offset, interhemifield). In the elementary-shape trials, there was no prime, and the test shape was a circle or an ellipse. Using the method of adjustment, the percent elongation [(longer diameter - shorter diameter)/(shorter diameter) x100] of the reproduced ellipse was computed.

RESULTS

The mean percent elongation in response to the elementary shapes did not vary with increasing age. The shape distortion effect decreased significantly with increasing age during both intra- and interhemifield conditions. The mean shape distortion effect was larger for the intrahemifield condition than for the interhemifield one.

CONCLUSION

The shape distortion effect decreases with advancing age while the perception of elementary shapes does not. These results indicate a severer age-related dysfunction of the cerebral processing of shape interaction than that of elementary-shape perception.

Schizophrenic subjects show deficient inhibition but intact task switching on saccadic tasks

BACKGROUND

Schizophrenic patients have executive function deficits, presumably on the basis of prefrontal cortex dysfunction. Although they consistently show impaired inhibition, the evidence of a task switching deficit is less consistent and is often based on performance of neuropsychological tests that require several cognitive processes (e.g., the Wisconsin Card Sort Test [WCST]). We investigated inhibition and task switching using saccadic tasks to determine whether schizophrenic patients have selective impairments of these executive functions.

METHODS

Sixteen normal and 21 schizophrenic subjects performed blocks of randomly mixed prosaccade and antisaccade trials. This gave rise to four trial types: prosaccades and antisaccades that were either repeated or switched. Response accuracy and latency were measured. Schizophrenic subjects also performed the WCST.

RESULTS

Schizophrenic subjects showed abnormal antisaccade and WCST performance. In contrast, task switching was normal and unrelated to either antisaccade or WCST performance.

CONCLUSIONS

The finding of intact task switching performance that is unrelated to other measures of executive function demonstrates selective rather than general impairments of executive functions in schizophrenia. The findings also suggest that abnormal WCST performance is unlikely to be a consequence of deficient task switching. We hypothesize that inhibition and task switching are mediated by distinct neural networks, only one of which is dysfunctional in schizophrenia.

Unilateral right parietal damage leads to bilateral deficit for high-level motion

Patients with right parietal damage demonstrate a variety of attentional deficits in their left visual field contralateral to their lesion. We now report that patients with right lesions also show a severe loss in the perception of apparent motion in their "good" right visual field ipsilateral to their lesion. Three tests of attention were conducted, and losses were found only in the contralesional fields for a selective attention and a multiple object tracking task. Losses in apparent motion, however, were bilateral in all cases. The deficit in apparent motion in the parietal patients supports previous claims that this relatively effortless percept is mediated by attention. However, the bilateral deficit suggests that the disruption is due to a bilateral loss in the temporal resolution of attention to transient events that drive the apparent motion percept.

The spatial resolution of visual attention

Two tasks were used to evaluate the grain of visual attention, the minimum spacing at which attention can select individual items. First, observers performed a tracking task at many viewing distances. When the display subtended less than 1 degrees in size, tracking was no longer possible even though observers could resolve the items and their motions: The items were visible but could not be individuated one from the other. The limiting size for selection was roughly the same whether tracking one or three targets, suggesting that the resolution limit acts independently of the capacity limit of attention. Second, the closest spacing that still allowed individuation of single items in dense, static displays was examined. This critical spacing was about 50% coarser in the radial direction compared to the tangential direction and was coarser in the upper as opposed to the lower visual field. The results suggest that no more than about 60 items can be arrayed in the central 30 degrees of the visual field while still allowing attentional access to each individually. Our data show that selection has a coarse grain, much coarser than visual resolution. These measures of the resolution of attention are based solely on the selection of location and are not confounded with preattentive feature interactions that may contribute to measures from flanker and crowding tasks. The results suggest that the parietal area is the most likely locus of this selection mechanism and that it acts by pointing to the spatial coordinates (or cortical coordinates) of items of interest rather than by holding a representation of the items themselves.

The spoke brightness illusion originates at an early motion processing stage

When a bright white disk revolves around a fixation point on a gray background, observers perceive a "spoke": a dark gray region that connects the disk with the fixation point. Our first experiment suggests that motion across the retina is both necessary and sufficient for spokes: The illusion occurs when a disk moves across the retina even though it is perceived to be stationary, but the illusion does not occur when the disk appears to move while remaining stationary on the retina. A second experiment shows that the strength of the illusion decreases with decreasing luminance contrast until subjective equiluminance, where little or no spoke is perceived. These results suggest that spokes originate at an early, predominantly luminance-based stage of motion processing, before the visual system discounts retinal motion caused by smooth pursuit.

Able to name, unable to compare: the visual abilities of a posterior split-brain patient

A patient with a lesion of the posterior half of the corpus callosum correctly named simple (e.g. colors) and complex (e.g. faces) stimuli whether presented to one or both hemifields. Although proficient at these tasks, and also able to make same/different judgements for stimuli within an hemifield, he failed dramatically when required to compare stimuli between the two hemifields. These results indicate that, while the posterior portion of the corpus callosum may not be essential for naming visual stimuli, it is essential for comparing stimuli between the two visual fields.

Wakes and spokes: new motion-induced brightness illusions

Under certain conditions, high-contrast moving figures induce adjacent illusory regions, 'wakes' and 'spokes', which have contrast polarity opposite the inducing figures. In this paper we document properties of these novel phenomena. When the illusions are induced by a moving bar, spokes appear on the side of the bar closer to fixation and connect the bar to the fixation point, regardless of the momentary position of the bar or whether it is moving to the left or to the right. Although spokes often extend up to the fixation point, they never extend beyond it. This is not due to blocking of the spoke's spread by the fixation point, because in another experiment spokes extend directly through an intervening figure. Whereas spokes emanate from the end of a horizontally moving bar closest to fixation, wakes emanate from the end farthest from fixation. In contrast to spokes, wakes do not show a towards-fixation bias. Instead, the wake's end trails the position of the bar, like a ship's wake. The higher the bar velocity, the more the end of the wake appears to trail it, suggesting that wakes are caused by a process which spreads from the edge of moving figures. Wakes and spokes, as distinct illusions, should provide significant constraints on theories of human motion and brightness perception processes.

Spatial representation in the normal visual field: a study of hemifield line bisection

We examined bisection of lines viewed in only one hemifield by normal subjects. Subjects first performed a traditional version of line bisection, by indicating the perceived midpoint of a line on paper with a penmark. Bisection was accurate when they were allowed to shift their gaze over the stimulus, but it was biased towards the central visual field (centripetally) when gaze was fixed so that the line was seen in only one hemifield. In a second experiment, lines with transectors at various locations were presented briefly on a screen and subjects had to indicate on which side of the perceived midpoint the transector was located. A centripetal bias was still found, indicating that it has a perceptual origin. The interaction between bias and effects of tangent line presentation suggested that subjects were performing an angle bisection rather than a line bisection. Also, there was bias in not only right and left hemifields but also upper and lower hemifields. In a third experiment, increasing the width of the stimulus bars peripherally did not eliminate this bias. Bias was size-invariant along the horizontal meridian. This spatial version of Weber's law was modeled by a magnification function using an exponential equation. The slope of this function is much shallower than those currently known for V1, V4 and V5. We conclude that a centripetal bias exists for hemifield line bisection and that this bias likely contributes to the contralateral bias of line bisection by hemianopic patients found in other studies.

Complete sparing of high-contrast color input to motion perception in cortical color blindness

It is widely held that color and motion are processed by separate parallel pathways in the visual system, but this view is difficult to reconcile with the fact that motion can be detected in equiluminant stimuli that are defined by color alone. To examine the relationship between color and motion, we tested three patients who had lost their color vision following cortical damage (central achromatopsia). Despite their profound loss in the subjective experience of color and their inability to detect the motion of faint colors, all three subjects showed surprisingly strong responses to high-contrast, moving color stimuli--equal in all respects to the performance of subjects with normal color vision. The pathway from opponent-color detectors in the retina to the motion analysis areas must therefore be independent of the damaged color centers in the occipitotemporal area. It is probably also independent of the motion analysis area MT/V5, because the contribution of color to motion detection in these patients is much stronger than the color response of monkey area MT.

A real-time method for generating random-dot motion displays of specified coherence

A method that allows the creation of moving random-dot patterns with any desired level of motion coherence is presented. In the present context, a random-dot pattern with 100% coherence is a sliding sheet of dots (all dots move at the same speed and in the same direction). A random-dot pattern with 0% coherence is visual dynamic noise (similar to detuned TV snow). Coherences between 100% and 0% have a specific percentage of the dots moving coherently together, while the remaining 'twinkle' in a random fashion. The use of look-up table animation allows the dot patterns to move smoothly and rapidly even on computers that lack computational speed. Additionally, the coherence of the motion in a particular region of the screen is determined by the spatial arrangement of pixel indices in that local region. Therefore, this technique allows different regions of the screen to have different levels of coherence which makes the creation of motion-defined shapes straightforward. The basics of look-up table animation are discussed and a general algorithm for creating motion with any level of coherence is presented.

Perceptual learning of orientation discrimination by more than one attribute

Using a perceptual learning paradigm, we evaluated whether information from the attributes: color, luminance and motion is combined to provide orientation coding. Four observers were trained to discriminate the orientation between color-defined bars, four between luminance-defined bars, and four between motion-defined bars. Before and after training, they were tested with each of the three attributes separately and all superimposed, at the same and at a different location as the one seen during training. A similar improvement was found whether the bars seen after training were defined by the same, or by a different attribute as the one seen during training, or by the three attributes superimposed. This improvement was significantly more substantial at the location where the bars were presented during training. Moreover, orientation discrimination was always better when the bars were defined by three attributes than by any one alone. Because the improvement was retinotopic and not restricted to the attribute seen during training, we suggest that training changed the sensitivity of orientation-selective cells responsive to color, luminance and motion. Moreover, the overall better performance with additional attributes supported an integration of information from color, luminance, and motion at a common site for orientation coding.

Attentional resolution and the locus of visual awareness

Visual spatial resolution is limited by factors ranging from optics to neuronal filters in the visual cortex, but it is not known to what extent it is also limited by the resolving power of attention. To investigate this, we studied adaptation to lines of specific orientation, a process that occurs in primary visual cortex. When a single grating is presented in the periphery of the visual field, human observers are aware of its orientation, but when it is flanked by other similar gratings ('crowding'), its orientation becomes impossible to discern. Nevertheless, we show that orientation-specific adaptation is not affected by crowding, implying that spatial resolution is limited by an attentional filter acting beyond the primary visual cortex. Consistent with this, we find that attentional resolution is greater in the lower than in the upper visual field, whereas there is no corresponding asymmetry in the primary visual cortex. We suggest that the attentional filter acts in one or more higher visual cortical areas to restrict the availability of visual information to conscious awareness.

Asymmetries in Brightness and Darkness for Assimilation and Simultaneous Contrast?

Recently, de Weert and Spillmann (1995 Vision Research35 1413 – 1419) reported a striking example of assimilation. Their stimulus was a pincushion formed by four arcs, each consisting of a number of black and white rings on a gray background (the area surrounded by the rings, see their figure 1). When the gray background is immediately surrounded by white rings, the background appears lighter and vice versa. When a subject is asked to match the luminance of a circle in a different spatial location for both the ‘lighter’ and the ‘darker’ pincushion, the matching luminance of the test is lower than the actual background luminance. This result is surprising but also counterintuitive. For example if a ‘light’ pincushion is matched with a ‘dark’ pincushion, it is expected that the luminance of a ‘light’ pincushion needs to be decreased in order to match the ‘dark’ pincushion. Conversely, the luminance of the ‘dark’ pincushion needs to be increased to match the ‘light’ pincushion. Therefore luminance values on both sides of the default background luminance are expected.

We replicated their basic experiment and found the same results. In additional conditions, we had subjects adjust the background luminance of a ‘light’ pincushion compared to a ‘dark’ and vice versa. In that case the luminance values were symmetrical on either side of the default background luminance. It would seem that the method of testing is crucial here. Therefore we also tested simultaneous contrast stimuli (all rings were made black or white) using the circle-match-task as in their original experiment. We found that both values were nicely distributed on both sides of the background luminance value, indicating that de Weert and Spillmann's finding is not attributable to the test condition as such.

Two different readers in the same brain after a posterior callosal lesion

Two different types of reading, one in each hemifield, were exhibited by a patient with a lesion of the posterior half of the corpus callosum. The patient read normally when words and non-words were presented to his right visual field. However, with left visual field presentations, the patient could not read non-words and vocalized real words very slowly, especially abstract words, inflected verbs and function words. He often replaced concrete words by semantic associates. Such an abnormal reading pattern is similar to that known as deep dyslexia. This unilateral deficit reveals the competence of the right hemisphere to initiate some semantic processing and its inability to manage phonological coding. The hypothesis that deep dyslexia is due to right hemisphere reading is reinforced by the present case.

On the relationship between background EEG and the P300 event-related potential

Background EEG was recorded from 24 subjects under eyes open/closed conditions for 5 min. The P3(00) event-related brain potential (ERP) was elicited with auditory stimuli when eyes were open/closed in the same subjects. Target stimulus probability was manipulated (0.20, 0.40, 0.60, 0.80) in different blocks under each eyes open/closed condition. Spectral analysis indicated that EEG power between 8 and 12 Hz demonstrated a similar scalp distribution as the P3 component of the ERP for the electrode sites employed. Spectral power and mean frequency were modestly correlated with P3 amplitude and peak latency primarily in the slower EEG bands, with associations observed across probability conditions and often strongest when target stimulus probability was .20. The results suggest that differences between individuals for EEG variation may contribute to P3 component variability, especially at the parietal recording site and under low target stimulus probability conditions when the P3 is largest and most stable.