Academic journal article Attention, Perception and Psychophysics

Effects of Direct and Averted Gaze on the Subsequent Saccadic Response

Academic journal article Attention, Perception and Psychophysics

Effects of Direct and Averted Gaze on the Subsequent Saccadic Response

Article excerpt

Published online: 14 March 2014

© Psychonomic Society, Inc. 2014

Abstract The saccadic latency to visual targets is susceptible to the properties of the currently fixated objects. For example, the disappearance of a fixation stimulus prior to presentation of a peripheral target shortens saccadic latencies (the gap effect). In the present study, we investigated the influences of a social signal from a facial fixation stimulus (i.e., gaze direction) on subsequent saccadic responses in the gap paradigm. In Experiment 1, a cartoon face with a direct or averted gaze was used as a fixation stimulus. The pupils of the face were unchanged (overlap), disappeared (gap), or were translated vertically to make or break eye contact (gaze shift). Participants were required to make a saccade toward a target to the left or the right of the fixation stimulus as quickly as possible. The results showed that the gaze direction influenced saccadic latencies only in the gaze shift condition, but not in the gap or overlap condition; the direct-to-averted gaze shift (i.e., breaking eye contact) yielded shorter saccadic latencies than did the averted-to-direct gaze shift (i.e., making eye contact). Further experiments revealed that this effect was eye contact specific (Exp. 2) and that the appearance of an eye gaze immediately before the saccade initiation also influenced the saccadic latency, depending on the gaze direction (Exp. 3). These results suggest that the latency of target-elicited saccades can be modulated not only by physical changes of the fixation stimulus, as has been seen in the conventional gap effect, but also by a social signal from the attended fixation stimulus.

Keywords Eye contact . Gap effect . Gaze perception . Saccade

High visual acuity in the human eye is restricted to a small region in the central retina (the fovea); hence, people need to continually make saccades in order to grasp a visual scene. Thus, one critical factor to efficiently scan the visual field is how quickly we can move fixations from one location to another. The efficiency of saccadic travel has been examined by a target-elicited saccade paradigm, in which participants are asked to fixate one location initially and then to make a saccade toward a target that appears at another location.

Studies with the target-elicited saccade paradigm have suggested that various factors influence the saccadic latency. For instance, a bright target stimulus leads to a faster saccadic reaction than does a dim target (Boch, Fischer, & Ramsperger, 1984; Kalesnykas & Hallett, 1994; Reuter-Lorenz, Hughes, & Fendrich, 1991), suggesting that high-intensity stimuli reach one's perceptual threshold faster (Bell, Meredith, Van Opstal, &Munoz,2006). Target locations also matter: The distance (i.e., retinal eccentricity) and relative direction of a target from the initially fixated location affect saccadic latency. The sac- cadic latency is shorter when a target eccentricity is between approximately 1° and 10°, and it increases with smaller or larger eccentricities (Kalesnykas & Hallett, 1994). The sac- cadic latency also tends to be shorter when a target is present- ed in a horizontal direction than when it is presented in a vertical direction (Vernet, Yang, Gruselle, Trams, & Kapoula, 2009).

The influence of the target properties on the saccadic latency seems intuitive. However, the properties of the initial- ly fixated stimuli also influence the subsequent saccadic la- tency (Reuter-Lorenz et al., 1991; Vernet et al., 2009). In particular, if a fixation stimulus disappears shortly (approxi- mately 200 ms) before the presentation of a peripheral target (gap condition), the saccadic latency to the target is shorter than if the fixation stimulus had remained present (overlap condition). This phenomenon was first reported by Saslow (1967) and is termed the gap effect (e.g., Dorris & Munoz, 1995; Fischer & Ramsperger, 1984; Kalesnykas & Hallett, 1987; Kingstone & Klein, 1993; Reuter-Lorenz et al. …

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