Discrete vs. continuous processing: The fate of an incompletely processed perceptual dimension

A relevant issue in the debate on continuous vs. discrete processing of information is whether incompletely processed information does or does not affect a subsequent reaction. Two stimuli (SL, SR) were presented on eye level, subtending a visual angle of 45 degrees. SL was always inspected first, followed by a saccade to SR and finally by a same/different response. The fixation time of SL (TL), the saccadic time (TM) and the time from fixating SR to the response (TR) were separately measured. SL and SR consisted of two-dimensional stimuli (size and letter shape) constructed in such a way that encoding size took longer for one group and encoding shape took longer for another group of 10 subjects. All subjects were tested in three conditions: Shape was relevant in one, size in the second, and both dimensions were relevant in the third condition.

TL was less when encoding the relevant dimension was fast. When both dimensions were relevant, TL was about as long as when only the slow dimension was relevant, suggesting parallel and interference-free processing during TL. When only the slow dimension was relevant, TR (same) was much longer when the fast dimension differed. When the fast dimension was relevant, TR (same) was slightly longer when the slow dimension differed, which can be handled by either model. The experiment was repeated with three well-practiced and less variable subjects who carried out sufficient trials to measure TR as a function of TL. The results of this study were in line with the discrete model: A different slow and irrelevant dimension did not affect the same response regardless of the duration of TL. Interestingly, subjects were capable of retrieving the slow dimension, suggesting a code which can be used for retrieval but which does not affect the same/different response.     

The Eriksen flanker effect revisited.

Four studies are reported on the potential role of perceptual interference in a standard Eriksen flanker task. In the first study, incongruent flanker letters showed the usual effect on choice reaction time (CRT) to the target letter but had no effect on the visual fixation time (VFT) needed to distinguish target and flankers. In the second experiment, the effect of incongruent flankers was studied in the context of a same-different response in regard to the target letter and a subsequently presented single letter. The effect of incongruent flankers vanished at an interstimulus interval of 200 ms. In Experiment 3, the same-different task was used in the paradigm of the functional visual field with a target-flankers combination as stimulus on the left (SL) and a single letter as stimulus on the right side (SR) of the visual field. Flankers did neither affect VFT nor the same-different CRT suggesting that target selection may proceed during the saccade from SL to SR. In Experiment 4 effects were studied of flanker-to-target and target-to-single-letter similarity. Flanker-to-target similarity did neither affect VFT nor same-different CRT but target-to-single-letter similarity prolonged same-different CRT. Together, the results suggest parallel perceptual processing of target and flankers, followed by competition of responses to the target and to the incongruent flankers. In line with earlier research, processes of response selection and response competition appear not to be tied to VFT but to proceed in parallel with the saccade from SL to SR.     

Eye scanpaths during visual imagery reenact those of perception of the same visual scene

Eye movements during mental imagery are not epiphenomenal but assist the process of image generation. Commands to the eyes for each fixation are stored along with the visual representation and are used as spatial index in a motor‐based coordinate system for the proper arrangement of parts of an image. In two experiments, subjects viewed an irregular checkerboard or color pictures of fish and were subsequently asked to form mental images of these stimuli while keeping their eyes open. During the perceptual phase, a group of subjects was requested to maintain fixation onto the screen's center, whereas another group was free to inspect the stimuli. During the imagery phase, all of these subjects were free to move their eyes. A third group of subjects (in Experiment 2) was free to explore the pattern but was requested to maintain central fixation during imagery. For subjects free to explore the pattern, the percentage of time spent fixating a specific location during perception was highly correlated with the time spent on the same (empty) locations during imagery. The order of scanning of these locations during imagery was correlated to the original order during perception. The strength of relatedness of these scanpaths and the vividness of each image predicted performance accuracy. Subjects who fixed their gaze centrally during perception did the same spontaneously during imagery. Subjects free to explore during perception, but maintaining central fixation during imagery, showed decreased ability to recall the pattern. We conclude that the eye scanpaths during visual imagery reenact those of perception of the same visual scene and that they play a functional role.     

On the control of visual spatial attention: evidence from human electrophysiology

We used electrophysiological methods to track the deployment of visual spatial attention while observers were engaged in concurrent central attentional processing, using a variant of the attentional blink paradigm. Two visual targets (T₁, T₂) were presented at a stimulus onset asynchrony of either 200 ms or 800 ms. T₁ was a white digit among white letters presented on a dark background using rapid serial visual presentation at fixation. T₂ was another digit that was presented to the left or right of fixation simultaneously with a distractor digit in the opposite visual field, each followed by a pattern mask. In each T₂ display, one digit was red and one was green. Half of the subjects reported the red digit and ignored the green one, whereas the other half reported the green digit and ignored the red one. T₁ and T₂ were reported in one block of trials, and only T₂ in another block (order counterbalanced across subjects). Accuracy of report of T₂ was lower at short SOA than at long SOA when both T₁ and T₂ were reported, but was similar across SOA when only T₂ was reported. The electrophysiological results focused on the N2pc component, which was used as an index of the locus of spatial attention. N2pc was reduced in amplitude when subjects reported T₁, and particularly so at the short SOA. The results suggest that attention to T₁ interfered with the deployment of visual spatial attention to T₂.     

Regarding Scenes

ABSTRACT— When we view the visual world, our eyes flit from one location to another about three times each second. These frequent changes in gaze direction result from very fast saccadic eye movements. Useful visual information is acquired only during fixations, periods of relative gaze stability. Gaze control is defined as the process of directing fixation through a scene in real time in the service of ongoing perceptual, cognitive, and behavioral activity. This article discusses current approaches and new empirical findings that are allowing investigators to unravel how human gaze control operates during active real-world scene perception.     

Recall of letters from the left and right visual half-fields under unilater and bilateral presentation.

Bilateral presentation in the visual half-field greatly increases superiority of the right visual half-field in tachistoscopic recognition of words when fixation is controlled using a center digit. Two experiments explored left-right asymmetry with bilateral presentation on a visual half-field short-term memory task, with fixation controlled by a sequence of letters at fixation. A total of 40 subjects served in the two experiments, which compared recall under unilateral versus bilateral presentation to the visual half-field. Bilateral presentation increased over-all recall from the last serial position but did not alter asymmetry of the visual half-field. As in previous experiments, the superiority of the right visual half-field was greatest from the initial serial positions. It was concluded that asymmetry of the visual half-field on this recall task with controlled fixation depends primarily on masking and short-term memory but is independent of unilateral-bilateral presentation.     

Auditory psychomotor coordination and visual search performance

In Experiments 1 and 2, the time to locate and identify a visual target (visual search performance in a two-alternative forced-choice paradigm) was measured as a function of the location of the target relative to the subject's initial line of gaze. In Experiment 1, tests were conducted within a 260 degree region on the horizontal plane at a fixed elevation (eye level). In Experiment 2, the position of the target was varied in both the horizontal (260 degrees) and the vertical (+/- 46 degrees from the initial line of gaze) planes. In both experiments, and for all locations tested, the time required to conduct a visual search was reduced substantially (175-1,200 msec) when a 10-Hz click train was presented from the same location as that occupied by the visual target. Significant differences in latencies were still evident when the visual target was located within 10 degrees of the initial line of gaze (central visual field). In Experiment 3, we examined head and eye movements that occur as subjects attempt to locate a sound source. Concurrent movements of the head and eyes are commonly encountered during auditorily directed search behavior. In over half of the trials, eyelid closures were apparent as the subjects attempted to orient themselves toward the sound source. The results from these experiments support the hypothesis that the auditory spatial channel has a significant role in regulating visual gaze.     

视觉表象眼动的变化：知识还是技能表征的差异？

以表象看到一个运动员完成三级跳远项目为实验任务,对表象任务的信息通达水平、眼动注视点的活动位置和被试对三级跳远项目的知识水平和技能水平进行系统的操纵,通过2个实验探讨了视觉表象眼动的变化是基于知识学习表征差异还是技能训练表征差异的问题。实验1以没有三级跳远运动专业技能知识且对该运动的认知水平也较低的大学生为被试,结果表明,在完成高信息通达水平的表象任务时,注视点需要较短的持续时间,但眼跳距离会增大,眼跳频率会变低;实验2对表象任务的知识学习表征水平和技能训练表征水平进行操纵,分别以对实验任务进行过知识学习和专业技能训练的人为被试,结果表明,随着被试知识习得水平和技能水平表征能力的提高,不同表象任务信息通达水平间的眼动差异将消失,但知识学习和技能表征的差异在平均眼跳时间上有差异,技能训练型的被试其平均眼跳时间要短于知识学习型被试,达到临界水平显著,注视点平均持续时间和平均眼跳距离等均没有差异。     

A perceptual-economy account for the inverted-optimal viewing position effect

In reading, fixation durations are longer when the eyes fall near the center of words than when fixation occurs toward the words' ends-the inverted-optimal viewing position (I-OVP) effect. This study assessed whether the I-OVP effect was based on the fixation position in the word or the fixation position in the visual stimulus. In Experiments 1-3, words were presented at variable locations within longer strings of symbols. On trials with short fixation durations, there were effects of fixation position in the string. When long fixations were made, there were effects of fixation position in the word. In Experiment 4, an I-OVP effect was found for meaningless number strings, and its strength depended on the task's processing demands. The findings show that (a) the I-OVP effect is unrelated to orthographic informativeness and (b) the eyes are not constrained to spend more time at the center of visual stimuli. These results support a perceptual-economy account: Fixations are held longer when the eyes are estimated to be at locations in words/stimuli in which greater amounts of information are anticipated. Implications for eye movements in reading are discussed.     

Conceptual processing of text during skimming and rapid sequential reading

Potential conceptual processing difficulties associated with abbreviating the duration of eye fixations during reading were explored using a rapid sequential visual presentation (RSVP) paradigm in which each word of a text was briefly presented (for as little as 86 msec) at a fixed location. Question answering and accuracy of summaries associated with RSVP were found to be inferior to performance obtained when subjects skimmed conventionally presented passages. RSVP performance was enhanced by inserting brief pauses between sentences. The pauses produced only minor changes in the perceptual characteristics of RSVP, but they probably allowed subjects to more readily process information that had been buffered in working memory. These results imply that eye fixation durations in conventional reading reflect the time constraints of conceptual processing operations (as well as constraints of planning and initiating eye movements), but also that these conceptual operations may be distributed over later fixations and even postponed until a syntactic boundary is reached.     

Do 5% changes around maximal lactate steady state lead to swimming biophysical modifications?

Our purpose was to examine the swimming biophysical responses at velocities (v) of 97.5, 100 and 102.5% of the maximal lactate steady state (MLSS). Ten elite female swimmers performed three-to-five 30-min constant tests at imposed paces to determine 97.5, 100 and 102.5%MLSS v. Gas exchange, blood lactate concentration ([La-]), stroke rate (SR) and v were determined during each test. The v values at 97.5, 100 and 102.5%MLSS were 1.21 ± 0.07, 1.24 ± 0.07 and 1.27 ± 0.07 m.s⁻¹, respectively. Oxygen uptake (V̇O₂) and Pulmonary ventilation (V̇E) increased as function of v. SR and stroke length (v/SR = SL) increased as a function of v. All measured variables were constant as a function of time at 97.5%MLSS and 100%MLSS. At 102.5%MLSS SR increased (3.5%) and stroke length (SL) decreased (3.5%) as a function of time. While V̇O₂ was constant at 102.5%MLSS, [La-] and V̇E increased as a function of time, suggesting hyperventilation, at v’s of 97.5%MLSS and 100%MLSS swimmers completed the 30 min swim in spite of decreased SL and increased SR. However, the decrease in SL and increased SF were accompanied by increased [La-] and V̇E and resulted in the inability of most swimmers to complete the 30 min swim presumably due to fatigue at 102.5%MLSS.     

Individual differences in face memory and eye fixation patterns during face learning

This study examined the relationship between individual differences in face memory and eye fixation patterns during face learning. Participants watched short movies of 20 faces and were divided into high and low face memory groups based on their performance in a recognition memory test. No qualitative difference was observed in the eye fixation distribution between high and low groups. Both groups mostly fixed on the internal region of faces, especially the eyes. A difference in the eye fixation pattern by groups was observed in the number of fixations and total fixation time on the eyes, which reflected high face memory participants moving their eyes between the left and right eyes more frequently than low face memory participants. These findings suggest that fixation on the eyes has a functional role in face memory and is related to individual differences in face memory.     

Eye movement control during scene viewing: Immediate degradation and enhancement effects of spatial frequency filtering

What controls how long the eyes remain fixated during scene perception? We investigated whether fixation durations are under the immediate control of the quality of the current scene image. Subjects freely viewed photographs of scenes in preparation for a later memory test while their eye movements were recorded. Using the saccade-contingent display change method, scenes were degraded (Experiment 1) or enhanced (Experiment 2) via blurring (low-pass filtering) during predefined saccades. Results showed that fixation durations immediately after a display change were influenced by the degree of blur, with a monotonic relationship between degree of blur and fixation duration. The results also demonstrated that fixation durations can be both increased and decreased by changes in the degree of blur. The results suggest that fixation durations in scene viewing are influenced by the ease of processing of the image currently in view. The results are consistent with models of saccade generation in scenes in which moment-to-moment difficulty in visual and cognitive processing modulates fixation durations.     

Eye movement control during reading: Evidence for direct control

In three experiments, subjects read text as their eye movements were monitored and display changes in the text were made contingent upon the eye movements. In one experiment, a window of text moved in synchrony with the eyes. In one condition, the size of the window was constant from fixation to fixation, while in the other condition the size of the window varied from fixation to fixation. In the other experiments, a visual mask was presented at the end of each saccade which delayed the onset of the text, and the length of the delay was varied. The pattern of eye movements was influenced by both the size of the window and the delay of the onset of the text, even when the window size or text delay was varying from fixation to fixation. However, there was also evidence that saccade length was affected by the size of the window on the prior fixation and that certain decisions to move the eye are programmed either before the fixation begins or are programmed during the fixation but without regard to the text fixated on. The results thus provide support for a mixed control model of eye movements in reading, in which decisions about when and where to move the eyes are based on information from the current fixation, the prior fixations, and possibly, other sources as well.     

Gaze behavior of trampoline gymnasts during a back tuck somersault

In trampolining, gymnasts perform a variety of rotational jumping elements and have to demonstrate perfect control of the body during the flying phase. The performance of a somersault should include an opening phase, i.e. the legs are fully extended pointing vertically at 180° called “kick-out”. As previous studies have shown, gaze behavior is essential for the controlling during the flight phase and to prepare for a perfect landing. Gymnasts supposedly use the trampoline bed as orientation and differences in gaze behavior can be expected, depending on how a somersault is performed. The present study investigates the gaze behavior of gymnasts during a back tuck somersault on the trampoline. Eleven experienced trampoline gymnasts performed back tuck somersaults with and without a kick-out while wearing a light weight portable eye-tracking device. All subjects fixated their gaze on a specific point at the trampoline bed and thus used visual information to prepare for landing. During the period of fixation, gymnasts' eyes moved continuously downwards to counteract the backwards head movement. The point of fixation differed between each somersault. Apparently, the fixation position depended on the gymnast's landing position in the bed. Performing a somersault with a kick-out allows gymnasts to orient themselves earlier and thus prepare sooner for landing. Unexpectedly, gymnasts of a higher performance class fixated the bed later compared to less experienced athletes. Supposedly, gymnasts of a better class can allow themselves to fixate later in order to optimize the form and execution of a somersault.     

More than meets the eye: the effect of planned fixations on scene representation

Scene memory frequently includes a swath of unseen layout beyond a photograph's boundaries (boundary extension [BE]; Intraub and Richardson, 1989). Might it be affected by the viewer's plan to shift fixation near a view boundary? When photographs were centrally fixated (500 msec), BE occurred following a 2-sec masked interval (Experiment 1). In Experiments 2-4, a cue during the first fixation signaled viewers to fixate an object near the left or right boundary. The picture was masked before the eyes landed. BE occurred on the cued side and on the top and bottom, but not on the uncued side. This relatively accurate performance on the uncued side suggests that inhibition of a movement to one side (in a competitive task) may also inhibit extrapolation of layout. BE on the to-be-fixated side, however, supports the idea that anticipatory representation of layout is an adaptive error that may aid the spatial integration of successive views.     

The developmental trajectory of children's auditory and visual statistical learning abilities: modality‐based differences in the effect of age

Infants, children and adults are capable of extracting recurring patterns from their environment through statistical learning (SL), an implicit learning mechanism that is considered to have an important role in language acquisition. Research over the past 20 years has shown that SL is present from very early infancy and found in a variety of tasks and across modalities (e.g., auditory, visual), raising questions on the domain generality of SL. However, while SL is well established for infants and adults, only little is known about its developmental trajectory during childhood, leaving two important questions unanswered: (1) Is SL an early‐maturing capacity that is fully developed in infancy, or does it improve with age like other cognitive capacities (e.g., memory)? and (2) Will SL have similar developmental trajectories across modalities? Only few studies have looked at SL across development, with conflicting results: some find age‐related improvements while others do not. Importantly, no study to date has examined auditory SL across childhood, nor compared it to visual SL to see if there are modality‐based differences in the developmental trajectory of SL abilities. We addressed these issues by conducting a large‐scale study of children's performance on matching auditory and visual SL tasks across a wide age range (5–12y). Results show modality‐based differences in the development of SL abilities: while children's learning in the visual domain improved with age, learning in the auditory domain did not change in the tested age range. We examine these findings in light of previous studies and discuss their implications for modality‐based differences in SL and for the role of auditory SL in language acquisition. A video abstract of this article can be viewed at: https://www.youtube.com/watch?v=3kg35hoF0pw .     

Visual mislocalisation induced by translational and radial background motion

Three experiments were conducted to explore how translational and radial background motion affected visual localisation. In experiment 1, subjects were asked to indicate the apparent position of a small spot of light flashing against a background of vertical stripes, at a varying point in time before and after rapid translational motion of the background to the left or right. When the spot was flashed before the background motion, subjects mislocalised it toward the central fixation point. An interesting finding was that this mislocalisation occurred in most cases when the background moved in the direction opposite to the visual half-field in which the spot was flashed. That is to say, a spot flashed on the right side of the fixation point was mislocalised when its background moved to the left, and not when it moved to the right; and the converse was also true. In experiment 2, concentric circles were used as the background, and moved in a contracting or expanding direction. The results indicated that mislocalisation toward the central fixation point occurred when a spot was flashed before contracting motion of the background. The same mislocalisation was observed for the spot flashed in the lower visual field, but not when it was flashed in the upper visual field (experiment 3). It is concluded that the mislocalisation is a visual illusion induced by a transient background motion toward the central fixation point.     

面孔部件在群体注意方向判断中的作用

探讨面孔部件(眼睛和鼻子)在个体和群体注意方向判断中的作用。实验1使用不同数量面孔的图片,要求报告群体或个体的注意方向。结果发现,多面孔条件下对群体注意方向估计的准确性高于单面孔条件。实验2采用眼动技术,探讨眼睛和鼻子在判断其注意方向时注视的空间与时间分布特征。结果发现,基于单张面孔判断时,对鼻子的总注视时间长于眼睛;基于多张面孔判断时,对眼睛和鼻子的总注视时间没有差异。整个研究表明,知觉个体注意主要依赖鼻子,知觉群体注意依赖眼睛和鼻子。     

Ratings of emotion in faces are influenced by the visual field to which stimuli are presented

This experiment was designed to assess the differential impact of initially presenting affective information to the left versus right hemisphere on both the perception of and response to the input. Nineteen right-handed subjects were presented with faces expressing happiness and sadness. Each face was presented twice to each visual field for an 8-sec duration. The electro-oculogram (EOG) was monitored and fed back to subjects to train them to keep their eyes focused on the central fixation point as well as to eliminate trials confounded by eye movement artifact. Following each slide presentation, subjects rated the intensity of the emotional expression depicted in the face and their emotional reaction to the face on a series of 7-point rating scales. Subjects reported perceiving more happiness in response to stimuli initially presented to the left hemisphere (right visual field) compared to presentations of the identical faces to the right hemisphere (left visual field). This effect was predominantly a function of ratings on sad faces. A similar, albeit less robust, effect was found on self-ratings of happiness (the degree to which the face elicited the emotion in the viewer). These data challenge the view that the right hemisphere is uniquely involved in all emotional behavior. The implications of these findings for theories concerning the lateralization of emotional behavior are discussed.