Visual marking in moving displays: feature-based inhibition is not necessary

Visual marking is a mechanism by which new visual stimuli can gain a selection advantage by the top-down attentional inhibition of stimuli already in the field. Previous work (Olivers, Watson, & Humphreys, 1999) has shown that, for moving stimuli, there must be a unique feature difference between the old items and the new items for marking to occur. The present study shows that this constraint is not necessary if the local spatial relationships between the old moving items remain constant. It is proposed that, with a fixed configuration, the old moving items can be grouped to form a single object. An inhibitory template set up to represent the object then coordinates the application of inhibition to the individual stimuli. Implications for the theory and ecological flexibility of visual marking are discussed.     

Coherence determines speed discrimination

The visual system must determine which elements in a scene to regard as parts of a single object and which to regard as different objects. We can create stimuli that are ambiguous, ie consistent with more than one interpretation, and ask in what situations the stimulus elements are interpreted as part of a single object and when they are interpreted as multiple objects. The ambiguous stimuli in this study were moving plaid patterns--the sum of two drifting gratings with different orientations. Observers may see a rigid coherent plaid object moving in one direction, or may see two gratings moving in different directions sliding over one another. When the gratings have similar contrasts they appear to cohere and only the plaid speed is perceptually available; when the gratings have different contrasts they appear to slide and only the speeds of the gratings are perceived. Coherence thus determines what speed information is passed to higher stages of motion processing. A two-stage model of plaid motion perception is presented which agrees with the model proposed by Adelson and Movshon and extends it, detailing the relationship between coherence and speed discrimination.     

Visual impressions of generative transmission

ABSTRACT

Previous research has shown that stimuli in which a moving object (A) contacts a stationary one (B) and stops, and object B then moves off in the same direction, give rise to a causal impression: object A is perceived as producing the motion of object B. This impression is weakened or does not occur if there is a delay between A contacting B and B moving, or if there is a spatial gap between B and the location at which A stops. It is shown that a strong causal impression can occur despite the presence of both gap and delay if there are cues to generative transmission of causal influence from A to B. The cues investigated were successive colour change of a series of objects filling the gap between A and B. Reported causal impressions were stronger with the colour change stimuli than with stimuli in which the objects were present but did not change colour, and stronger if the colour change proceeded from A to B than if it proceeded in the opposite direction. Reported causal impressions increased in strength as the number of objects involved in the colour change increased, consistent with the hypothesis that the colour change is a cue to a process of transmission, and inconsistent with the hypothesis that it is perceived or inferred as involving a chain of causal relations. Other kinds of changes to object properties—a small upward motion, shrinkage without moving, and disappearance—yielded similar results. It appears that any rapid sequential change in object properties in the direction of causal influence can function to give rise to the visual impression of generative transmission. The possible role of apparent motion is discussed.     

The threshold for sudden changes in the velocity of a seen object

The difference threshold for the velocity of a seen object was measured by the method of constant stimuli, using two categories. An approximate correspondence with Weber's law was found, the divergence from it appearing, in general, as an increase of the threshold at both ends of the range of initial velocities. The Mean Threshold (0-5 probability of perception, corrected for guessing) was, in favourable conditions, about 12 per cent, of the initial velocity. Whether the stimulus was an increase or a decrease of velocity made no marked difference. With two moving objects, which converged, crossed, and then diverged, both suffering the same change of velocity, the threshold was higher.

Velocity changes as low as 2 ± 5 per cent, elicited a significant proportion of correct responses. Some theoretical points in connection with this are discussed. Responses to blank stimuli showed a strong tendency to guess “slower,” which tendency differed significantly in degree between most of the experimental conditions. Tests with reduced exposure times showed that exposures could be as short as 0 ± 5 second (the velocity change occurring in the middle of the exposure) without appreciable detriment.     

Understanding the effects of moving visual stimuli on unilateral neglect following stroke

Moving visual stimuli have been shown to reduce unilateral neglect (ULN), however, the mechanisms underlying these effects remain poorly understood. This study compared lateralised and non-lateralised moving visual stimuli to investigate whether the spatial characteristics or general alerting properties of moving visual stimuli are responsible for reducing neglect. Post-stroke left neglect patients as well as healthy and patient control subjects were tested on a computerised line bisection task under six visual stimulus conditions. The key finding was that, relative to the no stimulus condition, leftward moving and left-sided moving visual stimuli shifted neglect patients' bisection errors leftward while the non-lateralised random moving visual stimuli did not reduce neglect patients' rightward bisection errors. The results provide evidence that spatial characteristics rather than general alerting properties of moving visual stimuli reduce rightward bisection errors in ULN. Moreover, the pattern of findings strongly supports the notion that moving visual stimuli reduce neglect by capturing attention and drawing it to a spatial location rather than by activating the attentional system via superior collicular neurons.     

Stimulus Movement and the Intensity of Attention

The Psychological Record - A stimulus movement effect has been reported in which learning by nonhuman animals was significantly better with moving than with stationary stimuli. In the present...     

Unimodal and crossmodal effects of endogenous attention to visual and auditory motion

Three experiments were conducted examining unimodal and crossmodal effects of attention to motion. Horizontally moving sounds and dot patterns were presented and participants’ task was to discriminate their motion speed or whether they were presented with a brief gap. In Experiments 1 and 2, stimuli of one modality and of one direction were presented with a higher probability ( p = .7) than other stimuli. Sounds and dot patterns moving in the expected direction were discriminated faster than stimuli moving in the unexpected direction. In Experiment 3, participants had to respond only to stimuli moving in one direction within the primary modality, but to all stimuli regardless of their direction within the rarer secondary modality. Stimuli of the secondary modality moving in the attended direction were discriminated faster than were oppositely moving stimuli. Results suggest that attending to the direction of motion affects perception within vision and audition, but also across modalities.     

Monkeys (Macaca mulatta and Cebus apella) track, enumerate, and compare multiple sets of moving items

Despite many demonstrations of numerical competence in nonhuman animals, little is known about how well animals enumerate moving stimuli. In this series of experiments, rhesus monkeys (Macaca mulatta) and capuchin monkeys (Cebus apella) performed computerized tasks in which they had to enumerate sets of stimuli. In Experiment 1, rhesus monkeys compared two sets of moving stimuli. Experiment 2 required comparisons of a moving set and a static set. Experiment 3 included human participants and capuchin monkeys to assess all 3 species' performance and to determine whether responding was to the numerical properties of the stimulus sets rather than to some other stimulus property such as cumulative area. Experiment 4 required both monkey species to enumerate subsets of each moving array. In all experiments, monkeys performed above chance levels, and their responses were controlled by the number of items in the arrays as opposed to nonnumerical stimulus dimensions. Rhesus monkeys performed comparably to adult humans when directly compared although capuchin performance was lower.     

Stimulus configuration and valence-enhanced pecking by neonatal chicks

Valence-enhanced pecking occurs when hatchling chicks preferentially peck at releasing stimuli that have been assigned increased releasing power or valence. Enhanced valence is assigned by another releasing stimulus—here a “pecking” arrow. Pecking movements by the arrow have two separate effects: the stimulation or release of pecking by chicks and releasing valence enhancement, that is, pecking directed to particular stimuli. Exposure of chicks to the moving arrow yields pecking significantly increased over that accruing to a stationary arrow. A distinctive stimulus placed on the floor at the tip of the arrow, or, most effective, attached to the tip of the moving arrow, produces enhanced valence: pecking by observing chicks that is selectively increased to matching stimuli.     

Working memory and the guidance of visual attention: Consonance-driven orienting

Two experiments investigated the potential role of the content of working memory in guiding visual attention. Experiment 1 showed that maintaining a shape in working memory resulted in a decisive preference for moving attention to the same shape in the background when those shapes were task irrelevant. Experiment 2 showed a similar preference for words that were semantically related to an item held in working memory. We suggest that keeping an item active in working memory automatically results in a tendency for attention to be “attracted” to stimuli that are related to that item either visually or semantically.     

Influence of early experience on processing 2D threatening pictures by European starlings (<Emphasis Type="Italic">Sturnus vulgaris</Emphasis>)

Stimuli such as visual representations of raptors, snakes, or humans are generally assumed to be universally fear-inducing in birds and considered as a product of evolutionary perceptual bias. Both naïve and experienced birds should thus react to such stimuli with fear reactions. However, studies on different species have shown the importance of experience in the development of these fear reactions. We hypothesized that the responses of adult European starlings to fear-inducing visual stimuli may differ according to experience. We compared the reactions of Hand-raised adults with no experience of predators to those of Wild-caught adults, with potentially extensive experience with predators. Three visual stimuli (i.e. human, raptor, snake) were broadcast to 17 birds as 2D pictures (displayed via a LCD screen) with different modalities of presentation: degree of proximity and with or without movement. The results reveal that the birds were particularly sensitive to proximity and movement, with more attention towards moving stimuli and more withdrawal for close stimuli. The human stimulus elicited attention in both the distant and moving modalities but, like the other stimuli, mostly withdrawal when it was close. Developmental experience appeared to influence the emotional level, as the Hand-raised birds reacted strongly to all stimuli and all modalities, contrarily to the WC birds which performed withdrawals almost only for close stimuli and attention to moving stimuli. Stimuli proximity and movement seemed, therefore, relevant features that elicited negative reactions in Wild-caught birds. The Hand-raised birds were equally attentive to both distant and moving stimuli. Thus the young birds showed no real discrimination. Early and later experiences may, therefore, influence birds’ reactions. Starlings may require experience with real threats to develop adaptive responses, i.e. limiting unnecessary loss of energy by fleeing in front of non-dangerous stimuli.     

Filtering by movement in visual search.

Search for a target defined by a conjunction of movement and form (e.g., an X moving up in a display of intermingled Os moving up and stationary Xs) is parallel. This result is also found if (a) the moving Os and target X move in unpredictable directions so that the moving stimuli do not form a clear perceptual group or (b) the nontarget Xs also move but in a known, different direction from the Os and target X. In contrast, search is slow and serial if the target may be unpredictably among either moving or stationary stimuli. These results suggest that a component of the visual system operates as a movement filter that can direct attention to stimuli with a common movement characteristic. The filtering cue can be moving (vs. stationary), or movement in 1 particular direction. The results do not support the view that attention can only be directed to groups defined by common fate.     

Motion as a natural category for pigeons: Generalization and a feature-positive effect

Three groups of pigeons were trained with a modified discriminative autoshaping procedure to discriminate video images of other pigeons on the basis of movement. Birds of all groups were shown the same video images of other pigeons, which were either moving or still. The group to whom food was presented only after moving images learned the discrimination very quickly. A second group, to whom food was given only after still images, and a pseudocategory group, to whom food was presented after arbitrarily chosen stimuli, showed no evidence of discrimination during acquisition training. Extinction conditions led to clear differences in peck rates to moving and still images in the second group but not in the pseudocategory group. The result is related to the feature-positive effect. Generalization tests showed that the discrimination performance was based on visual features of the stimuli but was invariant against changes of size, perspective, brightness, and color. Furthermore, discrimination was maintained when novel images of pigeons under different viewing angles and seven other types of motion categories were presented. It is argued that the discrimination is based not on a common motion feature but on motion concepts or high-order generalization across motion categories.     

Theory versus Data in Prediction and Correlation Tasks

Research on the ability to assess covariation traditionally has employed dichotomous variables as stimuli and has consistently reported a tendency to perceive covariation where none exists-a tendency exacerbated by prior beliefs about the existence of a relationship. A smaller, more recent literature reports relatively accurate performance when the stimuli are continuous. Five experiments are presented that employ continuous variables while exploring the case in which correlations in the data conflict with expectations. Based on recent findings, performance on a prediction task is used as the dependent measure. Experiment 1 shows a lack of reliance on the data, due primarily to a failure to base responses on a valid but nonintuitive predictor. From the remaining experiments this performance can be attributed to attentional and strategic factors during study and a reluctance to rely on predictors that lack a conceptual connection to the criterion.     

Behavioural arousal and its habituation in the squirrel fish, Holocentrus rufus: the role of the telecephalon

Squirrel fish were captured, maintained for 2 days and then tested for their responses to stimuli in laboratory aquaria. A tap on the side of the aquarium or a shadow moving overhead elicited an arousal response involving a reduction in opercular movements, movement of the pectoral fins, and erection of the spiny dorsal fin. This latter response, when regularly provoked by a moving shadow at 15-s intervals, decreased in duration and habituated. When fish were restricted in a wire mesh trough and the stimulus was the onset of illumination to one eye at 15-s intervals, responses were quantitatively similar although shorter in duration. A series of stimuli delivered to one eye until habituation followed by a series to the other eye reduced the duration of initial responses and the number of trials for habituation of responses to stimuli delivered to the second eye. Responses were equivalent regardless of which eye (left or right) was first presented with stimuli. Section of the telencephalic anterior commissure considerably restricted the transfer of information about experience of stimuli presented to the first eye. Commissural section, combined with unilateral lesions in the posterior-medial telencephalon, severely impaired habituation of responses to the contralateral eye. Lateral lesions had no effect. The results are discussed in relation to the visual projection in Holocentrus and telecephalic involvement in arousal and its habituation in teleosts as a whole.     

Visual change with moving displays: more evidence for color feature map inhibition during preview search

Preview search with moving stimuli was investigated. The stimuli moved in multiple directions, and preview items could change either their color or their shape before onset of the new (search) displays. In Experiments 1 and 2, the authors found that (a) a preview benefit occurred even when more than 5 moving items had to be ignored, and (b) color change, but not shape change, disrupted preview search in moving stimuli. In contrast, shape change, but not color change, disrupted preview search in static stimuli (Experiments 3 and 4). Results suggest that preview search with moving displays is influenced by inhibition of a color map, whereas preview search with static displays is influenced by inhibition of locations of old distractors.     

Visual impressions of forces between objects: Entraining,enforced disintegration,and shattering

When a moving object (A) contacts a stationary one (B) and Object B then moves, visual impressions of force occur along with a visual impression of causality. It is shown that findings about force impressions that occur with launching effect stimuli generalize to other forms of phenomenal causality, namely entraining, enforced disintegration, and shattering stimuli. In particular, evidence is reported for generality of the force asymmetry, in which the amount of perceived force exerted by Object A is greater than the amount of perceived resistance put up by Object B. Effects of manipulations of kinematic variables also resembled those found in previous experiments. Some unpredicted findings occurred. It is argued that these reflect a change in perceptual interpretation when both objects are in motion prior to contact, due to both objects being perceived as in autonomous motion. The results are consistent with a theoretical account in which force impressions occur by a process of matching kinematic information in visual stimuli to stored representations of actions on objects, which supply information about forces.     

Sensitivity to reward and punishment in major depressive disorder: Effects of rumination and of single versus multiple experiences

In the current study, we examined the postulation that rumination makes it difficult for depressed individuals to learn the exact probability that different stimuli will be associated with punishment. To do so, we induced rumination or distraction in depressed and never-depressed participants and then measured punishment and reward sensitivity with a probabilistic selection task. In this task, participants first learn the probability that different stimuli will be associated with reward and punishment. During a subsequent test phase in which novel combinations of stimuli are presented, participants’ sensitivity to reward is tested by measuring their tendency to select the stimuli that were most highly rewarded during training, and their sensitivity to punishment is tested by measuring their tendency to not select the stimuli that were most highly punished during training. Compared with distraction, rumination led depressed participants to be less sensitive to the probability that stimuli will be associated with punishment and relatively less sensitive to punishment than reward. Never-depressed participants and depressed participants who were distracted from rumination were as sensitive to reward as they were to punishment. The effects of rumination on sensitivity to punishment may be a mechanism by which rumination can lead to maladaptive consequences.     

Judgments of synchrony between auditory and moving or still visual stimuli.

The flash-lag effect is a visual illusion wherein intermittently flashed, stationary stimuli seem to trail after a moving visual stimulus despite being flashed synchronously. We tested hypotheses that the flash-lag effect is due to spatial extrapolation, shortened perceptual lags, or accelerated acquisition of moving stimuli, all of which call for an earlier awareness of moving visual stimuli over stationary ones. Participants judged synchrony of a click either to a stationary flash of light or to a series of adjacent flashes that seemingly bounced off or bumped into the edge of the visual display. To be judged synchronous with a stationary flash, audio clicks had to be presented earlier--not later--than clicks that went with events, like a simulated bounce (Experiment 1) or crash (Experiments 2-4), of a moving visual target. Click synchrony to the initial appearance of a moving stimulus was no different than to a flash, but clicks had to be delayed by 30-40 ms to seem synchronous with the final (crash) positions (Experiment 2). The temporal difference was constant over a wide range of motion velocity (Experiment 3). Interrupting the apparent motion by omitting two illumination positions before the last one did not alter subjective synchrony, nor did their occlusion, so the shift in subjective synchrony seems not to be due to brightness contrast (Experiment 4). Click synchrony to the offset of a long duration stationary illumination was also delayed relative to its onset (Experiment 5). Visual stimuli in motion enter awareness no sooner than do stationary flashes, so motion extrapolation, latency difference, and motion acceleration cannot explain the flash-lag effect.