The Effect of Bilateral Visual Fields on Word Recognition

Abstract

Previous research suggests a significant difference in word recognition time between the left and right visual fields, with word recognition and response time of the right visual field significantly faster than the left visual field. The current study investigated bilateral visual fields on word recognition time by means of an online computer program consisting of 55 participants. It was hypothesized that men would respond faster than women, and the right visual field reaction times would be faster than the left. Results indicate that sex had no significant effect on reaction time. However, words presented in the right visual field were responded to significantly faster than words in the left. Supporting previous findings of a right visual (left hemispheric) advantage.

The Effect of Bilateral Visual Fields on Word Recognition

When examining word recognition, there are a variety of factors that come into play. These factors include the role each hemisphere plays in terms of language processing as well as the physiology of the brain. Further, when examining word recognition one must further understand the assortment of variables that come into play when dealing with word recognition. These include, but are not limited to the handedness of participants in word recognition studies, the type of words that are being studies (for example words of differing length, commonly used words versus less commonly used words), the manner by which participants are attending to the stimuli that are being presented, and the manner that words are presented.

Understanding the role that each hemisphere of the brain plays in recognizing words, and the physiology of the brain is fundamental to the understanding of studies of word recognition. A primary tenet of neuropsychology is that the left hemisphere specializes in language, and language processing, while the right hemisphere plays less of a role in the processing of language (Grimshaw, 1998, Nicholls & Wood, 1998). It should also be noted that stimuli presented to the right visual field has direct access to the left hemisphere, while information presented to the left visual field must first go to the right hemisphere, cross the corpus callosum, and then be interpreted in the left hemisphere (Grimshaw, 1998, Nicholls & Wood, 1998). Because each hemisphere of the brain specializes in its own functions, one hypothesis is that the corpus callosum acts as a shield between hemispheres (Grimshaw, 1998). This hypothesis provides formal reasoning for the generally lowered reaction times that is often encountered when stimuli are presented to the left visual field (Nicholls, & Wood, 1998).

Handedness

Previous research has indicating the importance of handedness (which hand individuals prefer to use on typical everyday tasks) in word recognition. Research has indicated that cerebral lateralization plays a contributing factor in the processing of language. Specifically research has suggested that left handed individuals have weaker cerebral lateralization, thus the typical right visual field advantage that is shown in right handed individuals is not as predominant, and occasionally a left visual field advantage is seen in left handed individuals (Nicholls & Wood, 1998).

In a study conducted by Leventhal (1988) the role that cerebral dominance plays on the participant's ability to recognize words were examined. The participants consisted of both left and right handed undergraduate students. The participants were presented words to the left visual field and the right visual field that were either emotionally neutral or emotionally stimulating. Previous word recognition studies have found that prosody is generally influenced by the right hemisphere, while language is processed in the left hemisphere (Grimshaw, 1998).

Leventhal (1988) found that participants who were right-handed recognized more words presented in the right visual field than the left visual field, while left-handed participants recognized more words presented in the left visual field than the right. Overall, right-handed participants recognized more words than left-handed participants. Leventhal (1988) concluded that all participants were equally capable of recognizing words, but that a significant difference was found in reaction time between right-handed and left-handed participants.

Handedness obviously plays an integral role in determining reaction time in word recognition tasks. The primary question that is presented upon reviewing the research available is why this occurs. If the left hemisphere always dictates language processing, why is it that left handed individuals occasionally show more rapid word recognition when stimuli are presented to the left visual field? Research has suggested that left handed individuals experience weaker brain lateralization, which could pose a feasible answer to this dilemma (Nicholls, & Wood, 1998).

Attention

The effect that visual cues play on the role of word recognition is another variable that must be taken into account when examining word recognition. There have been studies that suggest that the right visual field has an advantage over the left visual field because words presented in the right visual field enjoy enhanced retinal attention versus stimuli presented in the left visual field (Batt, Underwood, & Bryden, 1995). As such a variety of studies have been developed to divert attention from the right visual field to the left in order to change the area of retinal attention from what is thought to be the right to the left, in order to determine if this retinal attention may play a role in word recognition.

Nicholls and Wood (1998) conducted a series of experiments to assess the contribution of attentional mechanisms to the right visual field advantage for word recognition. In the experiment the participants were presented with visual cues that were valid, invalid, or neutral. A valid cue was a cue that was shown in the same visual field as the stimulus was presented. Invalid cues were presented in the opposite visual field than the field that words are presented. Cues that were considered neutral were presented to both visual fields at the same time.

Results of the experiments indicated words presented to the right visual field were likely to have lower levels of error in identification, as well as faster reaction times. The cueing effect discussed earlier was stronger for the left visual field than for the right visual field, which indicates that the left hemisphere requires less attention to process words. The right visual field advantage appears to reflect the left hemisphere's enhanced capacity for processing verbal information. The asymmetrical effect