Jiye Shen

Distractor Ratio Influences Patterns of Eye Movements during Visual Search

We examined the flexibility of guidance in a conjunctive search task by manipulating the ratios between different types of distractors. Participants were asked to decide whether a target was present or absent among distractors sharing either colour or shape. Results indicated a strong effect of distractor ratio on search performance. Shorter latency to move, faster manual response, and fewer fixations per trial were observed at extreme distractor ratios. The distribution of saccadic endpoints also varied flexibly as a function of distractor ratio. When there were very few same-colour distractors, the saccadic selectivity was biased towards the colour dimension. In contrast, when most of the distractors shared colour with the target, the saccadic selectivity was biased towards the shape dimension. Results are discussed within the framework of the guided search model.

Visual search asymmetry: The influence of stimulus familiarity and low-level features

Wang, Cavanagh, and Green (1994) demonstrated a pop-out effect in searching for an unfamiliar target among familiar distractors (U—F search) and argued for the importance of a familiarity difference between the target and the distractors in determining search efficiency. In four experiments, we explored the generality of that finding. Experiment 1 compared search efficiency across a variety of target-distractor pairs. In Experiments 2, 3, and 4, we used Chinese characters and their transforms as targets and distractors and compared search performance between Chinese and non-Chinese participants. We demonstrated that search asymmetry and search efficiency in the U—F condition are influenced by the presence of low-level feature differences between the familiar and the unfamiliar stimuli. Our findings suggest that the familiarity of the distractors, rather than the familiarity difference between the target and the distractors, determines search efficiency. We also documented a counterintuitive familiarity-inferiority effect, suggesting that knowledge of search stimuli may, sometimes, be detrimental to search performance.

Peripheral and parafoveal cueing and masking effects on saccadic selectivity in a gaze-contingent window paradigm

The present study employed the gaze-contingent window paradigm to investigate parafoveal and peripheral cueing and masking effects on saccadic selectivity in a triple-conjunction visual search task. In the cueing conditions, the information shown outside the gaze-contingent window was restricted to the feature or feature pair shared between the target and a particular distractor type. In the masking conditions, no stimulus features were shown outside the window. Significant cueing and masking effects on saccadic selectivity were observed for saccades directed at items within the window, where all features were visible across experimental conditions. Cueing a particular feature or feature pair biased saccadic selectivity towards this feature or feature pair, while masking generally reduced saccadic selectivity. These findings support the concept of visual guidance being a preattentive process that operates in parallel across the display.

Saccadic Selectivity During Visual Search: The Influence of Central Processing Difficulty

Publisher Summary This chapter examines the robustness of guidance of eye movements during visual search. Visual search is one of the dominant paradigms used for investigating visual attention. In a typical visual search task, participants have to decide whether a search display contains a designated target among distractors (nontarget elements). Consistent with major visual search theories, experiments discussed in the chapter demonstrate that participants direct their saccades selectively during the search process, revealing a strong correspondence between target-distractor similarity and saccadic frequency toward the respective distractors. While the duration of current fixations increased with increasing target-distractor similarity, there was no evidence that saccadic selectivity was influenced by the target-distractor similarity of the previously fixated display item or the duration of the previous fixation. These findings are inconsistent with the predictions by the waiting-room model. The chapter manipulates the difficulty of the central discrimination by introducing a concurrent visual task and presenting a gaze-contingent moving foveal mask. Although manipulations substantially degraded the overall visual search performance, the magnitude of peripheral selection was not affected. This is not consistent with the notion that the central discrimination and the peripheral analysis share the same pool of attentional resources as suggested by the foveal load model. Thus, these experiments provide convergent evidence that peripheral selection is a robust process, largely independent of the central processing difficulty.

EFFECTS OF CONTEXT AND INSTRUCTION ON THE GUIDANCE OF EYE MOVEMENTS DURING A CONJUNCTIVE VISUAL SEARCH TASK

Publisher Summary This chapter explores the effects of contextual and instructional manipulations on visual search behavior in a conjunctive search task with a distracter-ratio manipulation. Participants eye movements were monitored when they performed the task. Results from the investigation demonstrated that block context modulates the temporal dynamics of visual search by shortening fixation durations, reducing the number of fixations, enhancing task-relevant subset selection, and as a result, yielding faster manual responses in those trials that were congruent with the block context than in incongruent trials. This chapter suggests that the presence of top-down influences associated with an instructional manipulation operates over and above any influences of context.

Modulation of distraction in ageing

A cueing paradigm was employed to examine modulation of distraction due to a visual singleton. Subjects were required to make a saccade to a shape-singleton target. A predictive location cue indicated the hemifield where a target would appear. Older adults made more anticipatory saccades than younger adults, and were less accurate for making an eye movement in the vicinity of a target. However, younger and older adults likewise benefited from the cue; distraction was reduced when the distractor singleton appeared in an uncued hemisphere. The ability to compensate for problems with distraction in older and younger adults through use of the precue suggests that attention to a general region of space, rather than a specific location, may be enough to modulate distraction.

Saccadic Selectivity During Visual Search

Publisher Summary This chapter examines the robustness of guidance of eye movements during visual search. Visual search is one of the dominant paradigms used for investigating visual attention. In a typical visual search task, participants have to decide whether a search display contains a designated target among distractors (nontarget elements). Consistent with major visual search theories, experiments discussed in the chapter demonstrate that participants direct their saccades selectively during the search process, revealing a strong correspondence between target-distractor similarity and saccadic frequency toward the respective distractors. While the duration of current fixations increased with increasing target-distractor similarity, there was no evidence that saccadic selectivity was influenced by the target-distractor similarity of the previously fixated display item or the duration of the previous fixation. These findings are inconsistent with the predictions by the waiting-room model. The chapter manipulates the difficulty of the central discrimination by introducing a concurrent visual task and presenting a gaze-contingent moving foveal mask. Although manipulations substantially degraded the overall visual search performance, the magnitude of peripheral selection was not affected. This is not consistent with the notion that the central discrimination and the peripheral analysis share the same pool of attentional resources as suggested by the foveal load model. Thus, these experiments provide convergent evidence that peripheral selection is a robust process, largely independent of the central processing difficulty.

Chapter 4 – Saccadic Selectivity During Visual Search: The Influence of Central Processing Difficulty

Publisher Summary This chapter examines the robustness of guidance of eye movements during visual search. Visual search is one of the dominant paradigms used for investigating visual attention. In a typical visual search task, participants have to decide whether a search display contains a designated target among distractors (nontarget elements). Consistent with major visual search theories, experiments discussed in the chapter demonstrate that participants direct their saccades selectively during the search process, revealing a strong correspondence between target-distractor similarity and saccadic frequency toward the respective distractors. While the duration of current fixations increased with increasing target-distractor similarity, there was no evidence that saccadic selectivity was influenced by the target-distractor similarity of the previously fixated display item or the duration of the previous fixation. These findings are inconsistent with the predictions by the waiting-room model. The chapter manipulates the difficulty of the central discrimination by introducing a concurrent visual task and presenting a gaze-contingent moving foveal mask. Although manipulations substantially degraded the overall visual search performance, the magnitude of peripheral selection was not affected. This is not consistent with the notion that the central discrimination and the peripheral analysis share the same pool of attentional resources as suggested by the foveal load model. Thus, these experiments provide convergent evidence that peripheral selection is a robust process, largely independent of the central processing difficulty.