The relationship between eye movements and spatial attention

Most previous studies of the attentional consequences of making saccadic eye movements have used peripheral stimuli to elicit eye movements. It is argued that in the light of evidence showing automatic “capture” of attention by peripheral stimuli, these experiments do not distinguish between attentional effects due to peripheral stimuli and those due to eye movements. In the present study, spatial attention was manipulated by varying the probability that peripheral probe stimuli would appear in different positions, while saccades were directed by a central arrow, enabling the effects of attention and eye movements to be separated. The results showed that the time to react to a peripheral stimulus could be shortened both by advance knowledge of its likely position and, separately, by preparing to make a saccade to that position. When the saccade was directed away from the most likely position of the probe, the targets for attention and eye movements were on opposite sides of the display. In this condition, the effects of preparing to make a saccade proved to be stronger than the effects of attentional allocation until well after the saccade had finished, suggesting that making a saccade necessarily involves the allocation of attention to the target position. The effects of probe stimuli on saccade latencies were also examined: probe stimuli that appeared before the saccade shortened saccade latencies if they appeared at the saccade target, and lengthened saccade latencies if they appeared on the opposite side of fixation. These facilitatory and inhibitory effects were shown to occur at different stages of saccade preparation and suggest that attention plays an important role in the generation of voluntary eye movements. The results of this study indicate that while it is possible to make attention movements without making corresponding eye movements, it is not possible to make an eye movement (in the absence of peripheral stimulation) without making a corresponding shift in the focus of attention.     

Multimodal events and moving locations: eye movements of adults and 6-month-olds reveal dynamic spatial indexing

The ability to keep track of locations in a dynamic, multimodal environment is crucial for successful interactions with other people and objects. The authors investigated the existence and flexibility of spatial indexing in adults and 6-month-old infants by adapting an eye-tracking paradigm from D. C. Richardson and M. J. Spivey (2000). Multimodal events were presented in specific locations, and eye movements were measured when the auditory portion of the stimulus was presented without its visual counterpart. Experiment 1 showed that adults spatially index auditory information even when the original associated locations move. Experiments 2 and 3 showed that infants are capable of both binding multimodal events to locations and tracking those locations when they move.     

Object-based eye movements: The eyes prefer to stay within the same object

The present study addressed the question of whether we prefer to make eye movements within or between objects. More specifically, when fixating one end of an object, are we more likely to make the next saccade within that same object or to another object? Observers had to discriminate small letters placed on rectangles similar to those used by Egly, Driver, and Rafal (1994). Following an exogenous cue, observers made a saccade to one end of one of the rectangles. The small target letter, which could be discriminated only after it had been fixated, could appear either within the same or at a different object. Consistent with object-based attention, we show that observers prefer to make an eye movement to the other end of the fixated same object, rather than to the equidistant end of a different object. It is concluded that there is a preference to make eye shifts within the same object, rather than between objects.     

Eye-hand coordination: spatial localization after saccadic and pursuit eye movements

Subjects produced speeded and unspeeded hand movements to a target location after either saccadic or pursuit eye movements to the target. Hand movements began either aligned with the initial position of gaze or from some other location. Subjects generally underestimated the extent of the pursuit eye movements relative to estimates made after saccades. With speeded hand movements, however, the underestimation was reduced considerably if the hand movements began aligned with a location other than the initial position of gaze. The results reveal details of the mechanisms underlying eye-hand coordination and show that important differences exist in the information used for localization for slow and rapid limb movements.     

The eyes know: eye movements as a veridical index of memory

In two experiments, we examined whether observers' eye movements distinguish studied faces from highly similar novel faces. Participants' eye movements were monitored while they viewed three-face displays. Target-present displays contained a studied face and two morphed faces that were visually similar to it; target-absent displays contained three morphed faces that were visually similar to a studied, but not tested, face. On each trial in a test session, participants were instructed to choose the studied face if it was present or a random face if it was not and then to indicate whether the chosen face was studied. Whereas manipulating visual similarity in target-absent displays influenced the rate of false endorsements of nonstudied items as studied, eye movements proved impervious to this manipulation. Studied faces were viewed disproportionately from 1,000 to 2,000 ms after display onset and from 1,000 to 500 ms before explicit identification. Early viewing also distinguished studied faces from faces incorrectly endorsed as studied. Our findings show that eye movements provide a relatively pure index of past experience that is uninfluenced by explicit response strategies, and suggest that eye movement measures may be of practical use in applied settings.     

Plasticity of human spatial cognition: spatial language and cognition covary across cultures

The present paper explores cross-cultural variation in spatial cognition by comparing spatial reconstruction tasks by Dutch and Namibian elementary school children. These two communities differ in the way they predominantly express spatial relations in language. Four experiments investigate cognitive strategy preferences across different levels of task-complexity and instruction. Data show a correlation between dominant linguistic spatial frames of reference and performance patterns in non-linguistic spatial memory tasks. This correlation is shown to be stable across an increase of complexity in the spatial array. When instructed to use their respective non-habitual cognitive strategy, participants were not easily able to switch between strategies and their attempts to do so impaired their performance. These results indicate a difference not only in preference but also in competence and suggest that spatial language and non-linguistic preferences and competences in spatial cognition are systematically aligned across human populations.     

Monitoring eye movements to investigate the picture superiority effect in spatial memory

Spatial memory is usually better for iconic than for verbal material. Our aim was to assess whether such effect is related to the way iconic and verbal targets are viewed when people have to memorize their locations. Eye movements were recorded while participants memorized the locations of images or words. Images received fewer, but longer, gazes than words. Longer gazes on images might reflect greater attention devoted to images due to their higher sensorial distinctiveness and/or generation with images of an additional phonological code beyond the visual code immediately available. We found that words were scanned mainly from left to right while a more heterogeneous scanning strategy characterized encoding of images. This suggests that iconic configurations tend to be maintained as global integrated representations in which all the item/location pairs are simultaneously present whilst verbal configurations are maintained through more sequential processes.     

Interactions between working memory, attention and eye movements

This paper reviews the recent findings on working memory, attention and eye movements. We discuss the research that shows that many phenomena related to visual attention taking place when selecting relevant information from the environment are similar to processes needed to keep information active in working memory. We discuss new data that show that when retrieving information from working memory, people may allocate visual spatial attention to the empty location in space that used to contain the information that has to be retrieved. Moreover, we show that maintaining a location in working memory not only may involve attention rehearsal, but might also recruit the oculomotor system. Recent findings seem to suggest that remembering a location may involve attention-based rehearsal in higher brain areas, while at the same time there is inhibition of specific motor programs at lower brain areas. We discuss the possibility that working memory functions do not reside at a special area in the brain, but emerge from the selective recruitment of brain areas that are typically involved in spatial attention and motor control.     

On the distinction between perception and cognition

To uphold the distinction between perception and cognition for certain classes of tasks or phenomena, it is proposed that three criteria must be met: (1) when perceptual and cognitive functions serve different biological purposes, (2) when stimulus information in dynamic events is necessary, but not sufficient for veridical perception, and (3) when the task emphasizes explicit retrieval, as opposed to implicit use of information. Conversely, when the three criteria have not been met, conditions for theoretical unification exist.     

Tracking without perceiving: a dissociation between eye movements and motion perception

Can people react to objects in their visual field that they do not consciously perceive? We investigated how visual perception and motor action respond to moving objects whose visibility is reduced, and we found a dissociation between motion processing for perception and for action. We compared motion perception and eye movements evoked by two orthogonally drifting gratings, each presented separately to a different eye. The strength of each monocular grating was manipulated by inducing adaptation to one grating prior to the presentation of both gratings. Reflexive eye movements tracked the vector average of both gratings (pattern motion) even though perceptual responses followed one motion direction exclusively (component motion). Observers almost never perceived pattern motion. This dissociation implies the existence of visual-motion signals that guide eye movements in the absence of a corresponding conscious percept.     

The eyes know what you are thinking: eye movements as an objective measure of mind wandering

Paralleling the recent work by Reichle, Reineberg, and Schooler (2010), we explore the use of eye movements as an objective measure of mind wandering while participants performed a reading task. Participants were placed in a self-classified probe-caught mind wandering paradigm while their eye movements were recorded. They were randomly probed every 2–3 min and were required to indicate whether their mind had been wandering. The results show that eye movements were generally less complex when participants reported mind wandering episodes, with both duration and frequency of within-word regressions, for example, becoming significantly reduced. This is consistent with the theoretical claim that the cognitive processes that normally influence eye movements to enhance semantic processing during reading exert less control during mind wandering episodes.     

Mind over muscle: the role of gaze control,spatial cognition,and the quiet eye in motor expertise

In the course of all motor behavior, the brain is limited in how much information it can process and act upon at a time. Performers must constantly decide where to look, what to attend to, and how to time fixated information with precisely controlled actions. The gaze can be directed to only one location at a time and information central to success must be selected from spatially complex environments, most often under severe time constraints. The coordination of these processes is explored in this Special issue in a number of motor tasks, including golf, soccer, law enforcement, and ballet. The papers describe the visual information and quiet eye characteristics that underlie the ability to make decisions under complex task conditions and the relationship between control of the gaze and task outcomes. With the attainment of motor expertise, measureable changes occur within the gaze, cognitive, and neural systems that are useful in training, rehabilitation, and the treatment of motor deficits.     

Moving from cognition to behavior: What the research says

In 1994, R. G. Lord and P. E. Levy proposed a variant of control theory that incorporated human information processing principles. The current article evaluates the empirical evidence for their propositions and updates the theory by considering contemporary research on information processing. Considerable support drawing from diverse literatures was found for propositions concerning the activation of goal-relevant information, the inhibition of goal-irrelevant information, and the consequences of goal completion. These effects were verified by meta-analytic analyses, which also supported the meaningfulness of such effects on the basis of their unstandardized magnitudes. The authors conclude by proposing new directions for this version of control theory by invoking recent theorizing on goal emergence and the importance of velocity and acceleration information for goal striving and by reviewing research in cognitive neuroscience.     

Culture and systems of thought: holistic versus analytic cognition

The authors find East Asians to be holistic, attending to the entire field and assigning causality to it, making relatively little use of categories and formal logic, and relying on "dialectical" reasoning, whereas Westerners are more analytic, paying attention primarily to the object and the categories to which it belongs and using rules, including formal logic, to understand its behavior. The 2 types of cognitive processes are embedded in different naive metaphysical systems and tacit epistemologies. The authors speculate that the origin of these differences is traceable to markedly different social systems. The theory and the evidence presented call into question long-held assumptions about basic cognitive processes and even about the appropriateness of the process-content distinction.     

Stimulus-response compatibility between stimulated eye and response location: implications for attentional accounts of the Simon effect

One influential theory of the Simon effect, the attention-shift hypothesis, states that attention movements are the origin of spatial stimulus codes. According to this hypothesis, stimulus-response compatibility effects should be absent when attention shifts are prevented. To test this prediction, we used monocular patches of color that required left or right key-press responses. About half of the subjects could discriminate which eye was stimulated (in a subsequent task), and showed strong spatial compatibility effects between the stimulated eye and the response location. The other half of the subjects could not make a utrocular discrimination (i.e., they could not judge which eye had received monocular stimulation), but the pattern of results was the same: the fastest reaction times were observed when the stimulated eye corresponded spatially to the required response (i.e., a Simon effect). Since the subjects presumably did not move their attention (from the subject's point of view, the stimuli were presented centrally), our results indicate that spatial codes can be produced in the absence of attention shifts. These results also show that utrocular discrimination can be assessed via indirect measures that are much more sensitive than explicit measures.     

Interactions between goal-directed eye and arm movements: arguments for an interdependent motor control

The accuracy of movements of the arm directed toward a point in space was investigated in healthy human subjects. To study the influence of the eye movement itself, on the guidance of the arm in the absence of any visual context, subjects performed the goal-directed arm movements without visual feedback about the arm displacement and the target position. The subjects were asked either to keep their eyes centered or oriented toward a previously flashed target. The analysis of the distribution of the errors in arm final position in the two conditions suggests that the eye movement influences the final position adopted by the arm. It is postulated that an interaction exists between the eye and arm systems during the motor program elaboration phase.