The central fixation bias in scene viewing: Selecting an optimal viewing position independently of motor biases and image feature distributions

Abstract

Observers show a marked tendency to fixate the center of the screen when viewing scenes on computer monitors. This is often assumed to arise because image features tend to be biased toward the center of natural images and fixations are correlated with image features. A common alternative explanation is that experiments typically use a central pre-trial fixation marker, and observers tend to make small amplitude saccades. In the present study, the central bias was explored by dividing images post hoc according to biases in their image feature distributions. Central biases could not be explained by motor biases for making small saccades and were found irrespective of the distribution of image features. When the scene appeared, the initial response was to orient to the center of the screen. Following this, fixation distributions did not vary with image feature distributions when freely viewing scenes. When searching the scenes, fixation distributions shifted slightly toward the distribution of features in the image, primarily during the first few fixations after the initial orienting response. The endurance of the central fixation bias irrespective of the distribution of image features, or the observer's task, implies one of three possible explanations: First, the center of the screen may be an optimal location for early information processing of the scene. Second, it may simply be that the center of the screen is a convenient location from which to start oculomotor exploration of the scene. Third, it may be that the central bias reflects a tendency to re-center the eye in its orbit.

Women gaze behaviour in assessing female bodies: the effects of clothing, body size, own body composition and body satisfaction

“…After the calibration procedure, the participant pressed the response box to initiate a trial. The trial was started with an FP displayed 10° left or right to the screen centre to minimize central fixation bias (Tatler, 2007). If the participant maintained fixation for 1 s, the FP disappeared and a testing image was presented at the centre of the screen.…”

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“…Provided the tight link between gaze and covert attention [10,20], tracking eye movements and measuring gaze allocation present one of the most promising paradigms for studying attentional processes in real-world vision. For a long time, experiments in this area were restricted to constrained laboratory settings, introducing biases [55], often neglecting head and body movements, and providing limited information for realworld situations [56]. Only recently, with the advent of powerful wearable eye trackers and virtual reality technology, real-world tasks and stimuli could be combined with less and less constrained settings.…”

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