Academic journal article Perception and Psychophysics

Deployment of Spatial Attention to Words in Central and Peripheral Vision

Academic journal article Perception and Psychophysics

Deployment of Spatial Attention to Words in Central and Peripheral Vision

Article excerpt

Four perceptual identification experiments examined the influence of spatial cues on the recognition of words presented in central vision (with fixation on either the first or last letter of the target word) and in peripheral vision (displaced left or right of a central fixation point). Stimulus location had a strong effect on word identification accuracy in both central and peripheral vision, showing a strong right visual field superiority that did not depend on eccentricity. Valid spatial cues improved word identification for peripherally presented targets but were largely ineffective for centrally presented targets. Effects of spatial cuing interacted with visual field effects in Experiment 1, with valid cues reducing the right visual field superiority for peripherally located targets, but this interaction was shown to depend on the type of neutral cue. These results provide further support for the role of attentional factors in visual field asymmetries obtained with targets in peripheral vision but not with centrally presented targets.

Reading is a complex process that involves extracting visual information from a currently fixated word while simultaneously preparing to extract information from peripherally located words in the text. Therefore, apart from the basic processes involved in extracting information from foveated visual stimuli, reading also involves managing eye movements and attentional resources in order to optimize information extraction across foveal and parafoveal vision. The present study examines the extent to which the appropriate allocation of spatial attention can facilitate word recognition and whether or not the allocation depends on eccentricity. First we review the main findings from past research involving the key manipulations of the present study: the effects of visual field (VF), viewing position (VP), and spatial cuing on visual word recognition.

VF Effects

A standard finding in the literature on visual word recognition is that words presented to the right visual field (RVF) are easier to recognize than words presented to the left visual field (LVF) (Bouma, 1973; Bradshaw & Nettleton, 1983; Lindell & Nicholls, 2003; Mishkin & Forgays, 1952; Nicholls & Wood, 1998; Orteils, Tudela, Noguera, & Abad, 1998). RVF superiority is observed in experimental conditions whose stimulus exposures are brief enough to prevent eye movements to the stimulus location,1 thus allowing researchers to rule out an explanation in terms of the speed with which a saccade can be planned and executed to the right as opposed to the left of fixation.

The prevailing interpretation of this RW advantage is that it reflects cerebral asymmetries in the processing of written language and, in particular, that written language is processed more efficiently by the left cerebral hemisphere (Bryden & Mondor, 1991). Given the structure of the visual system, RVF presentation provides direct access to the language centers located within the left hemisphere, whereas words presented in the LVF suffer from a processing delay equal to the time required to transmit information from the right to the left hemisphere (Kimura, 1966). Some initial support for this account was provided by the observation that left-lateralized subjects show a reduced RVF advantage (Brysbaert, 1994b; Hellige et al., 1994).

However, a popular alternative interpretation of VF asymmetries, one that is particularly relevant for the present study, is that they result from the manner in which spatial attention can be allocated across the VF (Kinsbourne, 1970; McCann, Folk, & Johnston, 1992; Mondor & Bryden, 1992; Nicholls & Wood, 1998; Orteils et al., 1998). According to this account, the RVF advantage would be caused by an attentional bias in favor of the RVF. This could result from scanning habits developed during the process of learning to read (Mishkin & Forgays, 1952). Key evidence in favor of this account was provided by Mishkin and Forgays, who showed that English words were better perceived in the RVF, whereas Yiddish words were better perceived in the LVF. …

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