Waldo reveals cultural differences in return fixations

ABSTRACT

Humans routinely perform visual search towards targets to adapt to the environment. These sequences of ballistic eye movements are shaped by a combination of top–down and bottom–up factors. Recent research documented that human observers display cultural-specific fixation patterns in a range of visual processing tasks. In particular, eye movement strategies extracting information from faces clearly differs between Western Caucasian (WC) and East Asian (EA) observers. However, whether such cultural differences are also present for visual scene processing remains debated. To this aim, we recorded the eye movements of WC and EA observers while they were solving visual search problems parametrically varying in difficulty: Where’s Waldo. Both groups had a comparable familiarity with the Waldo books reaching a comparable level of accuracy in target detection. Both cultural groups also showed a comparable temporal effect on inhibition of return, with longer fixation durations when saccades were performed to a return location compared to other locations. Westerners, however, located Waldo faster than Easterners. Interestingly, this modulation of speed was likely related to differences occurring on the low-level mechanisms of spatial inhibition of return, with EA observers returning more often to previously visited locations than the WC observers. This suboptimal eye movement strategy in the Easterners might be engendered by their cultural perceptual bias consisting in? a greater use of extra-foveal information. Overall, our data point towards the existence of a subtle, but significant difference in the processing of visual scenes across observers from different cultures during active visual search.     

Does oculomotor inhibition of return influence fixation probability during scene search?

Oculomotor inhibition of return (IOR) is believed to facilitate scene scanning by decreasing the probability that gaze will return to a previously fixated location. This "foraging" hypothesis was tested during scene search and in response to sudden-onset probes at the immediately previous (one-back) fixation location. The latencies of saccades landing within 1o of the previous fixation location were elevated, consistent with oculomotor IOR. However, there was no decrease in the likelihood that the previous location would be fixated relative to distance-matched controls or an a priori baseline. Saccades exhibit an overall forward bias, but this is due to a general bias to move in the same direction and for the same distance as the last saccade (saccadic momentum) rather than to a spatially specific tendency to avoid previously fixated locations. We find no evidence that oculomotor IOR has a significant impact on return probability during scene search.     

真实场景搜索中的眼动返回抑制

眼动返回抑制是指眼睛返回至先前注视过的位置(客体)时眼跳潜伏期长、可能性低的一种抑制现象。近年来, 研究者对真实场景搜索中的眼动返回抑制进行了深入的研究。本文介绍了相关研究的经典实验范式、主要发现及其理论解释, 探讨了眼动返回抑制的容量、眼动返回抑制是否具有任务特异性、场景搜索中是否存在眼动返回促进以及眼动返回抑制的神经基础等问题, 并指出未来该领域研究的方向和途径。     

The influence of cognitive load on spatial search performance

During search, executive function enables individuals to direct attention to potential targets, remember locations visited, and inhibit distracting information. In the present study, we investigated these executive processes in large-scale search. In our tasks, participants searched a room containing an array of illuminated locations embedded in the floor. The participants’ task was to press the switches at the illuminated locations on the floor so as to locate a target that changed color when pressed. The perceptual salience of the search locations was manipulated by having some locations flashing and some static. Participants were more likely to search at flashing locations, even when they were explicitly informed that the target was equally likely to be at any location. In large-scale search, attention was captured by the perceptual salience of the flashing lights, leading to a bias to explore these targets. Despite this failure of inhibition, participants were able to restrict returns to previously visited locations, a measure of spatial memory performance. Participants were more able to inhibit exploration to flashing locations when they were not required to remember which locations had previously been visited. A concurrent digit-span memory task further disrupted inhibition during search, as did a concurrent auditory attention task. These experiments extend a load theory of attention to large-scale search, which relies on egocentric representations of space. High cognitive load on working memory leads to increased distractor interference, providing evidence for distinct roles for the executive subprocesses of memory and inhibition during large-scale search.     

Automatic and intentional memory processes in visual search

Previous research has indicated that saccade target selection during visual search is influenced by scanning history. Already inspected items are less likely to be chosen as saccade targets as long as the number intervening saccades is small. Here, we adapted Jacoby’s (1991) process dissociation procedure to assess the role of intentional and automatic processes in saccade target selection. Results indicate a large automatic component biasing participants to move their eyes to unexamined locations. However, an intentional component allowed participants to both reinspect old items and aid their selection of new items. A second experiment examined inhibition of return (IOR) as a candidate for the observed automatic component. IOR was found for items that had been previously examined. It is concluded that both automatic and intentional memory traces are available to guide the eyes during search.     

Inhibitory tagging in an interrupted visual search

Inhibition of return facilitates visual search, biasing attention away from previously examined locations. Prior research has shown that, as a result of inhibitory tags associated with rejected distractor items, observers are slower to detect small probes presented at these tagged locations than they are to detect probes presented at locations that were unoccupied during visual search, but only when the search stimuli remain visible during the probe-detection task. Using an interrupted visual search task, in which search displays alternated with blank displays, we found that inhibitory tagging occurred in the absence of the search array when probes were presented during these blank displays. Furthermore, by manipulating participants’ attentional set, we showed that these inhibitory tags were associated only with items that the participants actively searched. Finally, by probing before the search was completed, we also showed that, early in search, processing at distractor locations was actually facilitated, and only as the search progressed did evidence for inhibitory tagging arise at those locations. These results suggest that the context of a visual search determines the presence or absence of inhibitory tagging, as well as demonstrating for the first time the temporal dynamics of location prioritization while search is ongoing.     

Probing distractor inhibition in visual search: inhibition of return

The role of inhibition of return (IOR) in serial visual search was reinvestigated using R. Klein's (1988) paradigm of a search task followed by a probe-detection task. Probes were presented at either the location of a potentially inhibited search distractor or an empty location. No evidence of IOR was obtained when the search objects were removed after the search-task response. But when the search objects remained on, a pattern of effects similar to Klein's results emerged. However, when just the search-critical object parts were removed or when participants received immediate error feedback to prevent rechecking of the search objects, IOR effects were observed only when probes appeared equally likely at search array and empty locations. These results support the operation of object-based IOR in serial visual search, with IOR demonstrable only when rechecking is prevented (facilitating task switching) and monitoring for probes is not biased toward search objects.     

Nomadic inhibition of attention and motor responses

Klein and MacInnes [Klein, R. M., & MacInnes, W. J. (1999). Inhibition of return is a foraging facilitator in visual search. Psychological Science, 10, 346-352] posited that the function of a phenomenon known as the inhibition of return (IOR) [Posner, M. I., & Cohen, Y. (1984). Components of visual orienting. In H. Bouma, & D. G. Bouwhuis (Eds.), Attention and performance X: Control of language processes (pp. 531-554). Hillsdale, NJ: Erlbaum] is to facilitate the foraging of food and objects in the environment. Once a target object has been identified either the location of that target in space or a movement to that target is inhibited in order to allow the performer to shift his/her attention to something new. Interestingly, in the majority of IOR studies, participants begin their search from a central home position. This research examined IOR in a nomadic target-target paradigm in which the home position randomly appeared at one of three target locations and attentional shifts/movements progressed to other locations. In Experiment 1, participants executed simple manual button presses in response to the sequential presentation of a home position and then two target stimuli. In Experiment 2, participants made manual-aiming movements in response to the same type of presentation. Results obtained from both experiments implicate perceptual-motor mechanisms over and above the inhibition of a specific target location or response. Inhibitory effects appear to be associated with both perceptual and motor processes, and depend not only on the temporal and spatial relations between potential targets, but also on the actions required to detect or engage the targets.     

Saccade preparation inhibits reorienting to recently attended locations

We measured manual reaction time in normal human subjects to confirm that an eccentric visual signal has a biphasic effect on covert attention and eye movements. First, it summons attention and biases a saccade toward the signal; a subsequent inhibition of return then slows responses to signals at that location. A temporal hemifield dominance for inhibition of return was shown; this finding converges with observations in neurologic patients to suggest that it is mediated by midbrain pathways. Endogenous orienting of attention, from a central arrow cue, did not activate inhibition of return, whereas endogenous saccade preparation did so as effectively as an exogenous signal, even when no saccade was made. Inhibition of return is activated by midbrain oculomotor pathways and may function as a location "tagging" mechanism to optimize efficiency of visual search.     

Value associations of irrelevant stimuli modify rapid visual orienting

In familiar environments, goal-directed visual behavior is often performed in the presence of objects with strong, but task-irrelevant, reward or punishment associations that are acquired through prior, unrelated experience. In a two-phase experiment, we asked whether such stimuli could affect speeded visual orienting in a classic visual orienting paradigm. First, participants learned to associate faces with monetary gains, losses, or no outcomes. These faces then served as brief, peripheral, uninformative cues in an explicitly unrewarded, unpunished, speeded, target localization task. Cues preceded targets by either 100 or 1,500 msec and appeared at either the same or a different location. Regardless of interval, reward-associated cues slowed responding at cued locations, as compared with equally familiar punishment-associated or no-value cues, and had no effect when targets were presented at uncued locations. This localized effect of reward-associated cues is consistent with adaptive models of inhibition of return and suggests rapid, low-level effects of motivation on visual processing.     

Vector averaging of inhibition of return

Observers detected targets presented 400 msec after a display containing one cue or two to four cues displayed simultaneously in randomly selected locations on a virtual circle around fixation. The cue arrangement was completely uninformative about the upcoming target’s location, and eye position was monitored to ensure that the participants maintained fixation between the cue and their manual detection response. Reflecting inhibition of return (IOR), there was a gradient of performance following single cues, with reaction time decreasing monotonically as the target’s angular distance from the cued direction increased. An equivalent gradient of IOR was found following multiple cues whose center of gravity fell outside the parafoveal region and, thus, whose net vector would activate an orienting response. Moreover, on these trials, whether or not the targeted location had been stimulated by a cue had little effect on this gradient. Finally, when the array of cues was balanced so that its center of gravity was at fixation, there was no IOR. These findings, which suggest that IOR is an aftermath of orienting elicited by the cue, are compatible with population coding of the entire cue (as a grouped array for multiple cues) as the generator of IOR.     

Revisiting the looking at nothing phenomenon: Visual and semantic biases in memory search

When visual stimuli remain present during search, people spend more time fixating objects that are semantically or visually related to the target instruction than looking at unrelated objects. Are these semantic and visual biases also observable when participants search within memory? We removed the visual display prior to search while continuously measuring eye movements towards locations previously occupied by objects. The target absent trials contained objects that were either visually or semantically related to the target instruction. When the overall mean proportion of fixation time was considered, we found biases towards the location previously occupied by the target, but failed to find biases towards visually or semantically related objects. However, in two experiments the pattern of biases towards the target over time provided a reliable predictor for biases towards the visually and semantically related objects. We therefore conclude that visual and semantic representations alone can guide eye movements in memory search, but that orienting biases are weak when the stimuli are no longer present.     

Facilitation of return in voluntary orienting to visual attributes1

Abstract: The present study examined the effects of voluntary and automatic orienting after a relatively long interval in an attentional cueing paradigm. Facilitation of return was observed after the voluntary orienting to a designated color (Experiment 1) and motion direction (Experiment 2), whereas inhibition of return was observed after the automatic orienting to an abrupt stimulus onset (Experiment 1). These results suggest that the voluntary orienting to a visual attribute modulates subsequent processes differently from the automatic orienting to an abrupt onset. In the voluntary orienting to visual attributes, it would be advantageous to return attention to the previously attended location, which is a potential source of information.     

Control of reflexive and voluntary saccades in the gap effect

In two experiments, we examined whether voluntary and reflexive saccades shared a common fixation disengagement mechanism, Participants were required to perform a variety of tasks, each requiring a different level of information processing of the display prior to execution of the saccade. In Experiment 1, participants executed either a prosaccade or an antisaccade upon detecting a stimulus array. In Experiment 2, participants executed a prosaccade to a stimulus array only if the array contained a target item. The target could be a line (easy search) or a digit (difficult search). The critical manipulation in both experiments was the relative timing between the removal of the fixation stimulus and the onset of the stimulus array. In both experiments, it was found that saccadic latencies were shortest when the fixation stimulus was removed before the onset of the stimulus array—a gap effect. It was concluded that reflexive and voluntary saccades share a common fixation disengagement mechanism that is largely independent of higher level cognitive processes.     

Control' of reflexive and voluntary saccades in the gap effect.

In two experiments, we examined whether voluntary and reflexive saccades shared a common fixation disengagement mechanism. Participants were required to perform a variety of tasks, each requiring a different level of information processing of the display prior to execution of the saccade. In Experiment 1, participants executed either a prosaccade or an antisaccade upon detecting a stimulus array. In Experiment 2, participants executed a prosaccade to a stimulus array only if the array contained a target item. The target could be a line (easy search) or a digit (difficult search). The critical manipulation in both experiments was the relative timing between the removal of the fixation stimulus and the onset of the stimulus array. In both experiments, it was found that saccadic latencies were shortest when the fixation stimulus was removed before the onset of the stimulus array--a gap effect. It was concluded that reflexive and voluntary saccades share a common fixation disengagement mechanism that is largely independent of higher level cognitive processes.     

Time window from visual images to visual short-term memory: consolidation or integration?

When two dot arrays are briefly presented, separated by a short interval of time, visual short-term memory of the first array is disrupted if the interval between arrays is shorter than 1300-1500 ms (Brockmole, Wang, & Irwin, 2002). Here we investigated whether such a time window was triggered by the necessity to integrate arrays. Using a probe task we removed the need for integration but retained the requirement to represent the images. We found that a long time window was needed for performance to reach asymptote even when integration across images was not required. Furthermore, such window was lengthened if subjects had to remember the locations of the second array, but not if they only conducted a visual search among it. We suggest that a temporal window is required for consolidation of the first array, which is vulnerable to disruption by subsequent images that also need to be memorized.     

场景情境和目标模板在视觉搜索中的交互作用

以真实场景图像中的物体搜索为实验任务, 操纵场景情境和目标模板, 采用眼动技术将搜索过程分为起始阶段、扫描阶段和确认阶段, 考察场景情境和目标模板对视觉搜索过程的影响机制。结果发现, 场景情境和目标模板的作用方式及时间点不同, 二者交互影响搜索的正确率和反应时, 仅场景情境影响起始阶段的时间, 随后二者交互影响扫描阶段和确认阶段的时间及主要眼动指标。作者由此提出了场景情境和目标模板在视觉搜索中的交互作用模型。     

Driving forces in free visual search: An ethology

Visual search typically involves sequences of eye movements under the constraints of a specific scene and specific goals. Visual search has been used as an experimental paradigm to study the interplay of scene salience and top-down goals, as well as various aspects of vision, attention, and memory, usually by introducing a secondary task or by controlling and manipulating the search environment. An ethology is a study of an animal in its natural environment, and here we examine the fixation patterns of the human animal searching a series of challenging illustrated scenes that are well-known in popular culture. The search was free of secondary tasks, probes, and other distractions. Our goal was to describe saccadic behavior, including patterns of fixation duration, saccade amplitude, and angular direction. In particular, we employed both new and established techniques for identifying top-down strategies, any influences of bottom-up image salience, and the midlevel attentional effects of saccadic momentum and inhibition of return. The visual search dynamics that we observed and quantified demonstrate that saccades are not independently generated and incorporate distinct influences from strategy, salience, and attention. Sequential dependencies consistent with inhibition of return also emerged from our analyses.     

视觉工作记忆对前注意阶段注意定向的调节

在注意阶段,视觉工作记忆与注意共享某些特征时,视觉工作记忆内容会引导注意定向。在前注意阶段的影响又是如何？对此问题的研究却很少见,本研究采用工作记忆与基于特征的视觉搜索相结合的任务深入探讨了此问题。研究结果发现：即使在前注意阶段,注意定向也会受到视觉工作记忆自上而下的调节。然而与注意阶段不同的是：当视觉工作记忆内容与随后视觉搜索任务的目标相关时,与记忆内容匹配的搜索项目会引导注意定向到该项目所在的位置,但只有此项目作为分心物时,才会明显地延迟对靶子的加工,而此项目作为靶子时,这种影响并不明显;当视觉工作记忆中保持的项目与随后视觉搜索任务的目标无关时,注意会忽略视觉工作记忆中保持的项目,有效地检测靶子     

Head-centred meridian effect on auditory spatial attention orienting

Six experiments examined the issue of whether one single system or separate systems underlie visual and auditory orienting of spatial attention. When auditory targets were used, reaction times were slower on trials in which cued and target locations were at opposite sides of the vertical head-centred meridian than on trials in which cued and target locations were at opposite sides of the vertical visual meridian or were not separated by any meridian. The head-centred meridian effect for auditory stimuli was apparent when targets were cued by either visual (Experiments 2, 3, and 6) or auditory cues (Experiment 5). Also, the head-centred meridian effect was found when targets were delivered either through headphones (Experiments 2, 3, and 5) or external loudspeakers (Experiment 6). Conversely, participants showed a visual meridian effect when they were required to respond to visual targets (Experiment 4). These results strongly suggest that auditory and visual spatial attention systems are indeed separate, as far as endogenous orienting is concerned.