Attentional capture by motion onsets is modulated by perceptual load

The onset of motion captures attention during visual search even if the motion is not task relevant, which suggests that motion onsets capture attention in a stimulus-driven manner. However, we have recently shown that stimulus-driven attentional capture by abruptly appearing objects is attenuated under conditions of high perceptual load. In the present study, we examined the influence of perceptual load on attentional capture by another type of dynamic stimulus: the onset of motion. Participants searched for a target letter through briefly presented low- and high-load displays. On each trial, two irrelevant flankers also appeared, one with a motion onset and one that was static. Flankers defined by a motion onset captured attention in the low-load but not in the high-load displays. This modulation of capture in high-load displays was not the result of overall lengthening of reaction times (RTs) in this condition, since search for a single low-contrast target lengthened RTs but did not influence capture. These results, together with those of previous studies, suggest that perceptual load can modulate attentional capture by dynamic stimuli.     

Distractor interference during smooth pursuit eye movements

When 2 targets for pursuit eye movements move in different directions, the eye velocity follows the vector average (S. G. Lisberger & V. P. Ferrera, 1997). The present study investigates the mechanisms of target selection when observers are instructed to follow a predefined horizontal target and to ignore a moving distractor stimulus. Results show that at 140 ms after distractor onset, horizontal eye velocity is decreased by about 25%. Vertical eye velocity increases or decreases by 1 degrees /s in the direction opposite from the distractor. This deviation varies in size with distractor direction, velocity, and contrast. The effect was present during the initiation and steady-state tracking phase of pursuit but only when the observer had prior information about target motion. Neither vector averaging nor winner-take-all models could predict the response to a moving to-be-ignored distractor during steady-state tracking of a predefined target. The contributions of perceptual mislocalization and spatial attention to the vertical deviation in pursuit are discussed.     

Crossmodal spatial attention shift produced by centrally presented gaze cues1

Abstract: Despite previous failures to identify visual‐upon‐auditory spatial‐cuing effects, recent studies have demonstrated that the abrupt onset of a lateralized visual stimulus triggers a shift of spatial attention in response to auditory judgment. Nevertheless, whether a centrally presented visual stimulus orients auditory attention remained unclear. The present study investigated whether centrally presented gaze cues trigger a reflexive shift of attention in response to auditory judgment. Participants fixated on a schematic face in which the eyes looked left or right (the cue). A target sound was then presented to the left or right of the cue. Participants judged the direction of the target as quickly as possible. Even though participants were told that the gaze direction did not predict the direction of the target, the response time was significantly faster when the gaze was in the target direction than when it was in the non‐target direction. These findings provide initial evidence for visual‐upon‐auditory spatial‐cuing effects produced by centrally presented cues, suggesting that a reflexive crossmodal shift of attention does occur with a centrally presented visual stimulus.     

Identification and categorization in visual search

Seven experiments were addressed to the general question of whether the identification of letters and numbers is a more rapid process than the categorization of such stimuli. Subjects were required to make a single response if a target stimulus specified by name (e.g., “A,” “2”) or designated by category class alone (e.g., “letter,” “number”) was presented in a trial. The principal findings were: (1) identification reaction times (RTs) were faster than categorization RTs: (2) RTs for targets shown without a context were faster than RTs for targets shown in the context of other stimuli; (3) identification RTs for targets shown in the context of stimuli from a different conceptual-taxonomic category were faster than RTs for targets shown in the context of stimuli from the same category only when target-context stimulus discriminability differencet were optimized. The results were interpreted in terms of a two-stage processing model in which context face,ors affect the duration of an initial encoding-scanning stage and search instruction (effective memory size) factors affect the duration of the memory comparison stage.     

What the experimenter’s prime tells the observer’s brain

The presentation of a stimulus below the threshold of conscious awareness can exert an influence on the processing of a subsequent target. One such consequence of briefly presented “primes” is seen in the negative compatibility effect. The response time (RT) to determine the left—right orientation of an arrow (i.e., the target) is relatively slow if a prime is also an arrow whose direction corresponds to that of the target. When the direction of the arrow is opposite that of the prime, RTs are relatively fast. In four experiments, we examined whether the prime shifts attention from the location of the subsequent target and whether this attention shift influences target processing. Results showed that the prime does indeed move attention. The consequence of this attention movement is that the representation of direction is affected. Specifically, RTs to process an arrow are shorter if the arrow’s direction is compatible with the last shift of attention. Furthermore, this interference occurs at a conceptual level concerning the representation of left and right rather than at the motor planning level. We argue that a shift in attention brought about by the prime can create a negative compatibility-like effect.     

Infant attention and the development of smooth pursuit tracking.

The effect of attention on smooth pursuit and saccadic tracking was studied in infants at 8, 14, 20, and 26 weeks of age. A small rectangle was presented moving in a sinusoidal pattern in either the horizontal or vertical direction. Attention level was distinguished with a recording of heart rate. There was an increase across age in overall tracking, the gain of the smooth pursuit eye movements, and an increase in the amplitude of compensatory saccades at faster tracking speeds. One age change was an increase in the preservation of smooth pursuit tracking ability as stimulus speed increased. A second change was the increasing tendency during attentive tracking to shift from smooth pursuit to saccadic tracking when the stimulus speed increased to the highest velocities. This study shows that the development of smooth pursuit and targeted saccadic eye movements is closely related to the development of sustained attention in this age range.     

Contextual cuing by global features

In visual search tasks, attention can be guided to a target item--appearing amidst distractors--on the basis of simple features (e.g., finding the red letter among green). Chun and Jiang's (1998) contextual cuing effect shows that reaction times (RTs) are also speeded if the spatial configuration of items in a scene is repeated over time. In the present studies, we ask whether global properties of the scene can speed search (e.g., if the display is mostly red, then the target is at location X). In Experiment 1A, the overall background color of the display predicted the target location, and the predictive color could appear 0, 400, or 800 msec in advance of the search array. Mean RTs were faster in predictive than in nonpredictive conditions. However, there was little improvement in search slopes. The global color cue did not improve search efficiency. Experiments 1B-1F replicated this effect using different predictive properties (e.g., background orientation-texture and stimulus color). The results showed a strong RT effect of predictive background, but (at best) only a weak improvement in search efficiency. A strong improvement in efficiency was found, however, when the informative background was presented 1,500 msec prior to the onset of the search stimuli and when observers were given explicit instructions to use the cue (Experiment 2).     

Attention maintains mental extrapolation of target position: irrelevant distractors eliminate forward displacement after implied motion

Observers' judgments of the final position of a moving target are typically shifted in the direction of implied motion ("representational momentum"). The role of attention is unclear: visual attention may be necessary to maintain or halt target displacement. When attention was captured by irrelevant distractors presented during the retention interval, forward displacement after implied target motion disappeared, suggesting that attention may be necessary to maintain mental extrapolation of target motion. In a further corroborative experiment, the deployment of attention was measured after a sequence of implied motion, and faster responses were observed to stimuli appearing in the direction of motion. Thus, attention may guide the mental extrapolation of target motion. Additionally, eye movements were measured during stimulus presentation and retention interval. The results showed that forward displacement with implied motion does not depend on eye movements. Differences between implied and smooth motion are discussed with respect to recent neurophysiological findings.     

情绪性注意与外源性注意的竞争作用

注意选择机制并不是一个单一的系统,而是多个具有不同选择标准和功能的复合系统.情绪性注意与外源性注意这两种注意选择过程是否可以同时作用,它们之间是否会相互干扰,抑或某一种注意过程是否占优势？本研究以30名在校大学生为被试,采用经典点探测任务的变式,对50ms和500ms两种SOA条件下,以愉快面孔和恐惧面孔作为情绪性注意的提示线索,对情绪性注意与外源性注意的相互关系进行探讨.发现两种注意是相互竞争的,都对注意产生效应.在短SOA条件下,恐惧面孔作为情绪性提示的线索时,情绪性注意和外源性注意会发生相互作用.而愉快面孔作为情绪性提示线索时,外源性注意更占主导作用.说明恐惧面孔比愉快面孔更能引发情绪性注意;在SOA为500ms时,情绪性注意和外源性注意均不再产生效应.再次说明,这两种注意是反射性、迅速的、自下而上的.     

How much processing do nonattended stimuli receive? Apparently very little, but...

The early versus late selection issue in attention models was examined by means of a new methodology. Through cues or precues, attention was directed to one location of a multistimulus visual display and, while attention was so engaged, the identity of a stimulus located at a different position in the display was changed. By varying the time after display onset before the stimulus was changed, we controlled the preview time that the original stimulus was represented on the retina. Then, using a marker cue, we directed the subject's attention to the location of the changed stimulus. The subject's response was a timed discrimination between two possible target letters. The data of main interest was the effect of preview time upon the subject's latency in identifying the new target that appeared in the changed location. We found that the preview time of the original stimulus, before RT was affected to the new target, depended upon whether the original stimulus was a neutral (noise) letter or whether it was the alternative target. When the original stimulus was a noise letter, RTs to the new target were just as fast as those obtained in the control condition in which the target was present throughout the preview interval and did not change its identity. Significant effects upon RT were obtained at preview times of 83 msec when the original stimulus was one of the targets that changed to the alternative target. Preview times also varied as a function of precuing. Preview times were correspondingly shortened when the first cue occurred 50 msec before display onset, thus providing an extra 50 msec for attention to be directed to the first display location. The results were interpreted in terms of two separate information-processing systems in the human: an automatic system and an attentional system. Even though a stimulus may have been automatically processed, when the attention system is directed to that stimulus, processing starts at the beginning again.     

Selective response activation can begin before stimulus recognition is complete: a psychophysiological and error analysis of continuous flow

In discussions of process models of human information processing, the continuous flow conception (Eriksen and Schultz 1979) plays a prominent role. A central prediction of this conception is that any information in a display associated with a response activates that response as soon as it becomes available in the perceptual system. If it concerns the correct response channel, then response facilitation occurs. If it concerns the incorrect response channel, then response competition occurs. To assess these mechanisms more directly, we used psychophysiological measures as well as reaction time (RT). We used the latency of the P3 component of the event related brain potential (ERP) as an index of stimulus evaluation duration, the onset of lateralized motor activity derived from the ERP as an index of selective central motor activation, and the onset of electromyographic activity as an index of the start of peripheral motor activation. Subjects were required to respond to target letters that were either flanked by letters that signalled the opposite response (incompatible arrays), by the target itself (compatible arrays), by letters not associated with a response (neutral arrays), or by no other letters (targets alone). Our results replicated the basic findings obtained in this paradigm. RTs to targets alone did not differ from RTs to compatible arrays. The latter were faster than RTs to neutral arrays, which were faster than RTs to incompatible arrays. P3 latencies were longer on incompatible than on neutral trials, and longer on compatible than on target alone trials. Incorrect central response activation on incompatible trials and correct central response activation on compatible trials, both began earlier than on target alone trials. Peripheral responding on both trial types, however, began later than on target alone trials. More incompatible but less compatible trials than neutral ones exhibited incorrect peripheral response activation. Peripheral response execution was faster and more accurate on compatible than on target alone trials, while it was slower and less accurate on incompatible than on neutral trials. These results indicate, that the flankers activated their associated response channel while display evaluation was still going on, and that response facilitation and competition occurred. After applying criteria proposed by Miller (1988), it was concluded that the set of stimulus recognition processes and the set of response activation processes cannot be regarded as independent stages of processing.     

线索提示对表征动量的影响

研究结合线索提示和表征动量范式,实验1、2均采用2有无线索(有线索,无线索)×4诱导期间时距(1250ms,1750ms,2250ms,2750ms)混合实验设计,探讨线索呈现的加工阶段和时距对表征动量的影响。实验1恒定保持间隔时距,在不同时距的诱导期间呈现线索,发现线索主效应不显著,但表征动量呈减小趋势;时距主效应不显著。实验2变化诱导时距,在恒定的保持间隔呈现线索,发生向后偏移现象,线索主效应显著;时距主效应不显著。研究结果表明,随着注意的增加,表征动量效应减小;注意时距不显著影响表征动量,而注意阶段显著影响表征动量。研究结果为表征动量的双加工理论提供了实证支持。     

The effect of blinks and saccadic eye movements on visual reaction times

Vision is suppressed during blinks and saccadic eye movements. We hypothesized that visual reaction times (RTs) in a vigilance test would be significantly increased when a blink or a saccade happened to coincide with the stimulus onset. Thirty healthy volunteers each performed a visual RT test for 15 min while their eye and eyelid movements were monitored by a system of infrared reflectance oculography. RTs increased significantly, many by more than 200 msec, when a blink occurred between 75 msec before and up to 150 msec after the stimulus onset. A similar result was observed with saccades that started 75 to 150 msec after the stimulus. Vision or attention was evidently inhibited before each blink and for longer than the saccades lasted. We suggest that visual suppression is involved in this process, which could explain some of the normal variability in RTs over periods of seconds that has not been adequately explained before.     

Automatic attentional orienting to other people’s gaze in schizophrenia

Explicit tests of social cognition have revealed pervasive deficits in schizophrenia. Less is known of automatic social cognition in schizophrenia. We used a spatial orienting task to investigate automatic shifts of attention cued by another person’s eye gaze in 29 patients and 28 controls. Central photographic images of a face with eyes shifted left or right, or looking straight ahead, preceded targets that appeared left or right of the cue. To examine automatic effects, cue direction was non-predictive of target location. Cue–target intervals were 100, 300, and 800?ms. In non-social control trials, arrows replaced eye-gaze cues. Both groups showed automatic attentional orienting indexed by faster reaction times (RTs) when arrows were congruent with target location across all cue–target intervals. Similar congruency effects were seen for eye-shift cues at 300 and 800?ms intervals, but patients showed significantly larger congruency effects at 800?ms, which were driven by delayed responses to incongruent target locations. At short 100-ms cue–target intervals, neither group showed faster RTs for congruent than for incongruent eye-shift cues, but patients were significantly slower to detect targets after direct-gaze cues. These findings conflict with previous studies using schematic line drawings of eye-shifts that have found automatic attentional orienting to be reduced in schizophrenia. Instead, our data indicate that patients display abnormalities in responding to gaze direction at various stages of gaze processing—reflected by a stronger preferential capture of attention by another person’s direct eye contact at initial stages of gaze processing and difficulties disengaging from a gazed-at location once shared attention is established.     

Gaze and arrow distractors influence saccade trajectories similarly

Perceiving someone's averted eye-gaze is thought to result in an automatic shift of attention and in the preparation of an oculomotor response in the direction of perceived gaze. Although gaze cues have been regarded as being special in this respect, recent studies have found evidence for automatic attention shifts with nonsocial stimuli, such as arrow cues. Here, we directly compared the effects of social and nonsocial cues on eye movement preparation by examining the modulation of saccade trajectories made in the presence of eye-gaze, arrows, or peripheral distractors. At a short stimulus onset asynchrony (SOA) between the distractor and the target, saccades deviated towards the direction of centrally presented arrow distractors, but away from the peripheral distractors. No significant trajectory deviations were found for gaze distractors. At the longer SOA, saccades deviated away from the direction of the distractor for all three distractor types, but deviations were smaller for the centrally presented gaze and arrow distractors. These effects were independent of whether line-drawings or photos of faces were used and could not be explained by differences in the spatial properties of the peripheral distractor. The results suggest that all three types of distractors (gaze, arrow, peripheral) can induce the automatic programming of an eye movement. Moreover, the findings suggest that gaze and arrow distractors affect oculomotor preparation similarly, whereas peripheral distractors, which are classically regarded as eliciting an automatic shift of attention and an oculomotor response, induce a stronger and faster acting influence on response preparation and the corresponding inhibition of that response.     

The effects of endogenous attention and stimulus onsets on encoding target location

The effects of endogenously attended and non-attended stimulus onsets on spatial stimulus encoding of a target were explored in a Simon task. In each experiment participants made speeded left or right key-press responses to the colour of a target that followed a cueing display consisting of several shapes. The target appeared within some shapes and not others. The target's spatial code as measured by a Simon task was its location relative to possible target positions and relative to the centre of the display. Target location was not coded relative to the positions of onset shapes that could not contain a target. These spatial coding effects were found at cue-target intervals of 50, 300, and 1000 ms. The data indicate that target location is defined relative to the distribution of endogenous attention and reference frames aligned with the centre of the display and that the spatial code assigned to a target is not affected when attention is shifted in the target's direction.     

Simon effect with and without awareness of the accessory stimulus

The authors investigated whether a Simon effect could be observed in an accessory-stimulus Simon task when participants were unaware of the task-irrelevant accessory cue. In Experiment 1A a central visual target was accompanied by a suprathreshold visual lateral cue. A regular Simon effect (i.e., faster cue-response corresponding reaction times [RTs]) was found. Experiment 1B demonstrated that this effect cannot be attributed to perceptual grouping of the target and cue. Experiments 2A, 2B, and 2C showed a reverse Simon effect (i.e., faster noncorresponding RTs) when participants were not aware of the cue. In this condition, the Simon effect would occur relative to the reorientation of attention from the cue, which would initially capture attention, toward the target. This conclusion is supported by the results of Experiments 3A and 3B, in which the reorientation of attention was induced by having the target flash after its onset. With suprathreshold cues either a reverse or regular Simon effect was observed by using a 100-ms or > or = 200-ms onset flashing interval, respectively, whereas with subthreshold cues a reverse Simon effect was found irrespective of the interval length.     

Sensitivity to stimulus similarity is associated with greater sustained attention ability

Sustained attention is critical for tasks where perceptual information must be continuously processed, like reading or driving; however, the cognitive processes underlying sustained attention remain incompletely characterized. In the experiments that follow, we explore the relationship between sustaining attention and the contents and maintenance of task-relevant features in an attentional template. Specifically, we administered the gradual onset continuous performance task (gradCPT), a sensitive measure of sustained attention, to a large web-based sample (N>20,000) and a smaller laboratory sample for validation and extension. The gradCPT requires participants to respond to most stimuli (city scenes – 90 %) and withhold to rare target images (mountain scenes – 10 %). By using stimulus similarity to probe the representational content of task-relevant features—assuming either exemplar- or category-based feature matching—we predicted that RTs for city stimuli that were more “mountain-like” would be slower and “city-like” mountain stimuli would elicit more erroneous presses. We found that exemplar-based target-nontarget (T-N) similarity predicted both RTs and erroneous button presses, suggesting a stimulus-specific feature matching process was adopted. Importantly, individual differences in the degree of sensitivity to these similarity measures correlated with conventional measures of attentional ability on the gradCPT as well as another CPT that is perceptually less demanding. In other words, individuals with greater sustained attention ability (assessed by two tasks) were more likely to be influenced by stimulus similarity on the gradCPT. These results suggest that sustained attention facilitates the construction and maintenance of an attentional template that is optimal for a given task.     

Fixation disengagement and eye-movement latency

We examined eye-movement latencies to a target that appeared during visual fixation of a stationary stimulus, a moving stimulus, or an extrafoveal stimulus. The stimulus at fixation was turned off either before target onset (gap condition) or after target onset (overlap condition). Consistent with previous research, saccadic latencies were shorter in gap conditions than they were in overlap conditions (the gap effect). In Experiment 1, a gap effect was observed for vergence eye movements. In Experiment 2, a gap effect was observed for saccades directed at a target that appeared during visual pursuit of a moving stimulus. In Experiment 3, a gap effect was observed for saccades directed at a target that appeared during extrafoveal fixation. The present results extend reports of the gap effect for saccadic shifts during visual fixation to (a) vergence shifts during visual fixation, (b) saccadic shifts during smooth visual pursuit, and (c) saccadic shifts during extrafoveal fixation. The present findings are discussed with respect to the incompatible goals of fixation-locking and fixation-shifting oculomotor responses.     

Effects of endogenous spatial attention on the detection and discrimination of spatial frequencies

Two experiments were designed to explore the relationship between visual attention and spatial-frequency processing using a cuing paradigm. In both experiments, the targets were a sharp-edged line segment with high spatial frequencies present and a blurred line segment with only low spatial frequencies present. In each trial an endogenous cue appeared at fixation indicating the probable location, left or right, in which a stimulus would appear. In experiment 1, a typical cuing effect was found with simple reaction times (RTs) for detecting the stimuli being faster when they appeared at a cued (ie attended) compared to an uncued (ie unattended) location. In experiment 2, choice RTs were measured, with participants indicating whether the sharp-edged line segment or the blurred line segment was presented in each trial. In this case, when it was necessary to process the spatial-frequency content of the stimuli, RTs were significantly faster at the attended location only for the sharp-edged line segment. For the blurred line segment without high spatial frequencies, RTs did not differ for attended and unattended locations. The results indicate that endogenous spatial attention interacts differently with high-spatial-frequency and low-spatial-frequency selective mechanisms depending on whether the task is to detect a stimulus or identify it on the basis of its spatial-frequency content.