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).
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).
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 of the cue suggests that attention does play an important role in perceptual asymmetries.
A similar study performed by Lindell and Nicholls (2003) which examined the effect of cue position on hemispheric performance. This study also found that cue position had no effect on left hemisphere performance, suggesting that the right visual field enjoys an attentional advantage. Reaction times for word identification were faster and with fewer errors in response to words in the right visual field than the left visual field (Lindell & Nicholls, 2003). Lindell and Nicholls (2003) also found that the right hemisphere showed a faciliatory effect of beginning cue, drawing spatial attention to the initial letter cluster, which enables efficient implementation of the right hemisphere’s sequential strategy.
Proverbio, Zani, and Avella (1997) investigated hemispheric specialization for spatial frequency processing by measuring reaction times to sinusoidal gratings in 12 healthy subjects. Results showed that reaction times were significantly faster in the left visual field than the right visual field for low frequency gratings and faster in the right visual field than the left visual field for high frequency gratings. Proverbio et al. (1997) found overall reaction times were faster to high frequency gratings, and also found a significant interaction between frequency and visual field. Proverbio’s (1997) results show that reaction times to targets in a selective attention task differ as a function of spatial frequency and visual field stimulation. These results indicate a hemispheric specialization for the ability to identify low versus high spatial frequency in a selective attention task (Proverbio et al., 1997).
Research has shown that a visual field difference exists in word recognition, with words presented in the right visual field processed more quickly and accurately than words presented in the left visual field (Eviatar, Ibrahim, & Ganayim, 2004; Iacoboni & Zaidel, 1996; Jordan & Patching, 2000; Leventhal 1988; Lindell & Nicholls, 2003). Words have been found to be processed more quickly when presented in the right visual field rather than the left visual field because for most people visual word recognition is achieved by neural mechanisms situated in the left hemisphere (Farid & Grainger, 1996).
Iacoboni and Zaidel (1996) compared behavioral laterality effect in a lexical decision making task using cued unilateral and bilateral presentations of different stimuli to right-handed undergraduate students. Words were found to be processed more quickly than nonwords in both visual fields, but words produce more accurate responses in the right visual field. Bilateral presentations were found to increase hemispheric independence in word recognition, with a bilateral presentation showing a word advantage in the right visual field and a nonword advantage in the left visual field (Iacoboni & Zaidel, 1996). Unilateral presentations showed a significant word advantage in the right visual field, but no significant differences in the left visual field. Overall, unilateral presentation produced more accurate and faster responses than bilateral presentation. High frequency words were recognized with more accuracy than low frequency words, wordness and word length interaction was found. Iacoboni & Zaidel’s (1996) hypothesis that after an initial similar perceptual process, words and nonwords are processed by independent, parallel processes was supported by the results of their study.
Jordan ; Patching (2000) studied the bilateral presentation of words in the left and right visual field, as well as nonlaterally. Nonlateral words were shown centrally to stimulate participant’s reaction to words presented in the right and left visual field, similar to a fixation point. These nonlateral words were incorporated to alter the perception of the words located in the left and right visual fields. Participants were rated on their accuracy to correctly recognize words that were presented simultaneously as the nonlateral word. These words were given a perceived identity of the actual word being presented in the left or right visual field. For example, “romp” and “ramp” were presented to the participant at the same time, and the participant was asked to recognize the word not presented in the center of the screen. Participants were able to more accurately report words on the right visual field. However, participants responded to words in the left visual field more problematically. Jordan and Patching’s (2000) findings also suggests that right visual field words frequently altered the perceived identity of the left visual field.
Word recognition has been found to be generally superior when the initial fixation point is left rather than right of the center of the word. Farid and Grainger (1996) compared the effects of initial fixation position in prefixed and suffixed words in both French and Arabic. In their study, Farid and Grainger (1996) found that the effects of initial fixation position produced an approximately U-shaped function on percent correct word identification scores, similar to previous research. Initial fixation position and morphological structure interacted significantly, which indicates that the effects of initial fixation position differed for the prefixed and suffixed stimuli (Farid ; Grainger, 1996). Initial fixations left of the center gave higher word identification accuracy than initial fixations right of the center, which supports the right visual field advantage (Farid ; Grainger, 1996).
Eviatar et al. (2004) tested bilingual participants fluent in both Hebrew and Arabic languages. The participants (native Hebrew and Arabic readers, fluent in Hebrew matching letters) were tested on their hemispheric abilities on lateralized versions of a letter-matching task. The task was to recognize these letters in the different visual fields. Eviatar et al. (2004) found that the Arabic readers had significantly more difficulty in recognizing Hebrew letters than did the Hebrew readers. Overall, participants performed slower at recognizing words on the left visual field than the right.
Therefore, words presented to the left visual field suffer a processing delay, because the information is first taken in by the right hemisphere and then must travel to the left hemisphere for processing (Farid ; Grainger, 1996). Bilateral presentation studies have been conducted in a variety of ways, all producing similar results: words presented in the right visual field processed more quickly and accurately than in the left visual field (Eviatar, Ibrahim, ; Ganayim, 2004; Iacoboni ; Zaidel, 1996; Jordan ; Patching, 2000; Leventhal 1988; Lindell ; Nicholls, 2003).
The type of word being studied is another prime factor when dealing with word recognition. A variety of studies have manipulated word length have found that words presented in the right visual field regardless of length tend to be recognized more readily than those in the left visual field (Ellis, Young, ; Anderson, 1988; Lavidor, ; Ellis, 2002; Lavidor, Ellis, ; Pansky, 2002). Other studies that have examined the frequency with which words appear in everyday language have found similar results in that words presented in the right visual field tend to be more readily recognized than those in the left (Bud, ; Lewine, 1988; Ohnesorge, ; Van Lancker, 2001; Voyer, 2003; Weems, ; Reggia, 2004).
Ellis, Young, and Anderson (1988) and Bub ; Lewine (1988) conducted similar studies examining word length on word recognition performance between the left and right visual hemifields. Word length was determined by how many letters were in the word presented. The researchers also manipulated what type of word being used: concrete and abstract nouns. All participants were right-handed adults, as to control for handedness. Ellis (1988) discovered that length affected responsiveness to words presented in the left visual field, but not to words in the right visual field. Results were also conclusive that both concrete and abstract nouns were responded to quicker in the right visual field, than the left. With the additional evidence from the study conducted by Bub (1988), indicates word length’s effect on word recognition in the right and left visual field is influenced by hemispheric specialization. Words that were longer in length took longer to recognize in the left visual field, where in the right visual field indicated a weaker effect demonstrating that participants were quicker to recognize words in the right visual field.
Lavidor and Ellis (2002) reanalyzed previous research to show that previously reported effects of word length affecting word recognition more in the left visual field than in the right visual field were confounded by orthographic neighborhood size. Lavidor and Ellis (2002) then manipulated length and orthographic neighborhood size in lateralized lexical decision tasks, and found that length and visual field interacted even with orthographic neighborhood size controlled, that orthographic neighborhood size affected responses to words in the left visual field but not the right visual field, and that when length and orthographic neighborhood size were combined, only lengths affected performance in the left visual field for words with few neighbors.
Lavidor, Ellis, and Pansky (2002) manipulated word length and letter case in English and Hebrew in order to study the effects of case alternation in two lateralized visual lexical decision experiments. Response times were found to be significantly faster when both English and Hebrew words were presented in the right visual field than the left. Response times were significantly faster and more accurate to 4-letter words than to 5- and 6- letter words. When presenting the stimuli in mixed case, performance was disrupted in the right visual field but not the left. Both the left and right visual fields were affected by word length when the word was presented in mixed case (Lavidor et al., 2002).
In a most interesting study conducted by Ohnesorge and Van Lancker (2001) studied a word recognition task involving common or uncommon proper nouns. Ohnesorge (2001) found that both hemispheres can process common proper nouns. However, the right hemisphere specifically recognized common proper nouns due to personal relevance. In addition, the researcher’s results supported that common proper nouns were recognized more than noncommon proper nouns. Furthermore, greater accuracy in recognizing common and uncommon nouns was found in the right visual field than the left visual field.
Voyer (2003) studied the role of the right hemisphere in word visual word recognition. Different types of words were used during this experiment testing participant’s ability to recognize high and low frequency words. High frequency words are words that occur often, while low frequency words occur not as often. Voyer (2003) found a significant word frequency effect only for left visual field presentation.
Weems and Reggia (2004) tested participants’ ability to recognize words versus non-words. Words were characterized by being neutral, and non-words were defined by being emotionally stimulating words. Weems (2004) found a consistent left hemispheric advantage for word recognition but not non-word recognition. Hemispheric advantages were studied and shown that right visual field recognition was significantly slower than left visual field recognition.
Throughout the literature that has been discussed various factors come into play when dealing with word recognition. Throughout all studies the predominating theme seems to be that words presented in the right visual field are recognized more readily than words in the left visual field. Therefore, the current study proposes that participants will display a lower reaction time to words presented in the right visual field (to the left hemisphere) than to words presented to the left visual field.
A convenient sample of 55 (29 women and 26 men, age range 11 to 60) volunteered to participate in the current study. Six participants were left handed, 47 were right handed, and 2 were ambidextrous, as determined by self report. Participants included Christopher Newport University students, Christopher Newport University alumni, friends, and relatives of the experimenters. Participants were not compensated for their participation. All participants were treated in accordance with the “Ethical Principles of Psychologists and Code of Conduct” (American Psychological Association, 1992).
Participants used their own computer that was connected to the internet in order to participate in the study. To begin this study, participants must download the necessary plug-in indicated as to have the appropriate system requirements: http://www.macromedia.com/shockwave/download/download.cgi?P1_Prod_Version=ShockwaveAuthorware;P5_Language=English. The website used to run the experiment is located at: http://psychexps.olemiss.edu/Exps/Word_Recognition/startwr.htm PsychExperiments is an online social and cognitive psychology laboratory, developed by funding from the U.S. Department of Education’s FIPSE program. The site consists of a variety of interactive experiments, a collective data archive, and downloadable support for materials that both participants and experimenters can use to gather data. Both sites can only be visited by a computer that is connected to the internet. In the current experiment, all data was collected using the PsychExperiments website.
Each participant accessed the website featuring the current experiment individually at a time convenient for them. Participants were given sufficient instructions (in either the form of email or printed out directions) about how to access the experiment. The experiment was accessed at psychexps.olemiss.edu. Participants were instructed to click on “participate in experiments,” located on the top left portion of the page. From there, participants were instructed to download the plug-in (located on the left side of the screen) necessary to install the program experiment on the participant’s computer. Then participants clicked on “Lab Experiments,” also located on the left side of the page. After that, participants were told to choose “Word Recognition Study,” and then to “Run Word Recognition Study.” Once the experiment was accessed, a description about the experiment and instructions on how to proceed were given by the program to participants. Participants were then given the option of participating. Participants who chose to participate then selected the appropriate region and project affiliationin the current study, participants were instructed to select the region including Virginia for their region, and “Velkey’s Project One” as their affiliation. After this, demographical data (including age, sex, and hand preference) was collected before the actual experiment began.
Once the experiment began, a total of 16 words were presented to each participant, with an indeterminate amount of trials because the experiment continued until the participant correctly identified all 16 words. To start each trial, the participant was prompted to press any key. To assure central fixation, a pulsating plus sign appeared in the beginning of the screen at the beginning of each trial. The pulsating plus sign stayed on the screen for 3-5 seconds and then a word was presented in either the left or right visual field, and then removed. The length of the time the word was presented depended on the number of times the word had been presented before. The participant was then prompted to type the word they saw flash on the screen. Once a word was correctly identified, it was removed from the words being presented. If the word was incorrectly identified, it was randomly presented again later in the experiment for a longer period of time. The experiment continued until all words had been correctly identified.
The position of words presented on the screen had a statistically significant effect on reaction time, F(1,53) = 17.654, p ; .001, h = .25. Participants’ mean recognition time for words presented on the left side of the screen .119 s, (SEM = .003). The mean recognition time for words presented on the right side of the screen was .108 s, (SEM = .002) (see figure 1). These results supported the experimenters’ hypothesis that words presented in the right visual field would be recognized more quickly than words in the left visual field.
There was no statistical significance found to suggest an interaction between position of words presented on sex of participants, F(1, 53) = 1.552, p = .218, h = .028. Further, no statistical significance was found to suggest that sex had an effect, F(1, 53) = .271, p = .605, h = .005. These results failed to support the hypothesis of the experimenters that males would display a mean recognition time that was more quickly than females.
Results of the current study support the researcher’s hypothesis that words presented in the right visual field were recognized more quickly than words presented in the left visual field. These findings are consistent with previous research indicating a right visual field advantage.
Several limitations were present in the current study. The convenient sample used in the current study was not representative of the population. In addition, not enough left-handed participants were included to study a handedness effect on word recognition. Previous research indicates that handedness has a significant effect on word recognition. Studies have shown that right-handed individuals have a stronger right visual field advantage than left-handed individuals because of weaker cerebral lateralization (Nicholls & Wood, 1998); some studies have even found left handed individuals exhibiting a left visual field advantage (Leventhal, 1988; Nicholls & Wood, 1998). Another problem which arose in the current study was accessing the project website. Many participants had problems downloading the required software plug-in in order to complete the experiment affecting the sample.
The current study expands upon existing literature in the field of cerebral lateralization by reproducing previous findings indicating a right visual field advantage in word recognition (Batt et al., 1995; Iacoboni & Zaidel, 1996; Leventhal, 1988; Jordan & Patching, 2000; Nicholls & Wood, 1998). Words presented in the right visual field were recognized more quickly overall than words presented in the left visual field.
Future research in the word recognition and hemispheric specialization could examine the affects of handedness on word recognition by sampling equal amounts of left and right handed individuals. The contradictory findings of an overall right visual field advantage on word recognition for both left and right-handed individuals can be further examined in this way.
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