The Effect Of Visual Function Compensation In Deaf People On Their Reading Processing

People can perceive the world through a multitude of sensory pathways.The information collected through various sensory pathways is crucial for successful exploration of the surrounding world.Will the development of additional sensory channels be influenced if one sensory channel of an individual is blocked? Deaf individuals,as a special group,cannot receive sound information from the outside world,hence they rely more on visual information to assure their everyday lives.What will happen to the deaf’s visual function in the long run?Regarding the impact of hearing loss on deaf people’s visual function,researchers have conducted numerous studies and proposed several theoretical hypotheses.Visual function compensation of deaf individuals means that,the deaf’s visual function will experience compensatory modifications to compensate for the lack of auditory information,resulting in improved visual performance.In terms of behavioral results,compared with age–matched hearing subjects,deaf people can detect visual stimuli from a wider range of vision（perceptual enhancement hypothesis）or react to them faster（reactivity enhancement hypothesis）,exhibiting spatial or temporal enhancement.Some researchers have also investigated the phenomenon from the standpoint of physiological mechanisms,discovering that it mostly occurs in supramodal functions,which can be completed by a variety of sensory channels（supramodal function hypothesis）,or visual functions represented by the dorsal visual pathway（dorsal route hypothesis）.Therefore,based on findings from visual perception tasks,the theory of deaf persons’ visual compensation may be summarized into four hypotheses from the perspectives of behavioral outcomes and physiological mechanisms.All four hypotheses agree that the vast majority of visual compensation emerges in parafoveal and peripheral areas.Reading,as a cognitive activity that is heavily reliant on visual information,is also impacted by compensation.Valid/irrelevant words in the parafoveal visual field will promote/interfere with the processing of foveal target words.The deaf’s parafoveal visual compensation allows them to have stronger promotion and interference effects,manifesting as a "double–edged sword" compensation consequence.During sentence reading,deaf readers extract parafoveal preview information more efficiently than hearing readers with equivalent reading ability,and they can also receive information from further texts.Researchers tend to believe that deaf readers’ visual function compensation in reading tasks may be accompanied by the redistribution of visual attention resources,that is,compared with hearing readers,deaf people allocate more visual attention resources to parafoveal visual field,and/or assign them to a further position.However,present hypotheses of deaf persons’ visual function compensation are drawn from findings of visual perception experiments,and the interpretation of reading tasks is still limited.Thus,this research aims to systematically explore the deaf readers’ visual function compensation in reading and then supplement the theory.Specifically,this paper investigated the effects of visual function compensation on deaf readers’ visual attention span,word recognition,and sentence reading by eye–tracking technology,in order to address three issues:（1）Whether deaf people’s visual function compensation will reveal a redistribution of visual attention resources.（2）What is the scope of the occurrence of deaf persons’ visual compensation?（3）Whether the parafoveal visual function compensation observed in deaf persons’ sentence reading can facilitate their foveal word recognition.In addition,referring to previous reading studies,two hearing control groups were used to minimize the impact of subjects’ reading skills and developmental characteristics: a chronological age matching group and a reading ability matching group.In the first study,three visual attention span experiments were conducted to determine whether deaf readers’ visual compensation was accompanied by the redistribution of visual attention resources.All three experiments adopted the visual 1–back paradigm,with symbols（Experiment 1）,numbers（Experiment 2）,and Chinese characters of varying complexity（Experiment 3）serving as experimental materials.Subjects were asked to determine whether the target stimulus in the center of the screen appeared in the preceding stimuli array,which was made up of five horizontally arranged stimuli.Throughout the experiment,subjects should keep their eyes fixated on the center of the screen,and the eye tracker was applied to record their gaze location.The capacity of participants to process several stimuli at the same time,known as visual attention span skill,could characterize the attentional distribution of deaf readers in foveal and parafoveal regions.In Experiment 1 and Experiment 3 high–complexity Chinese characters condition,there was no difference in the three groups’ visual attention span skills.In Experiment 2 and Experiment 3low–complexity Chinese characters condition,the ability of deaf persons to discriminate foveal stimuli was no different from that of the age–matched group but stronger than that of the reading ability–matched group;when it came to stimuli in the parafoveal area,there was no difference between deaf and reading–level matched readers.In conclusion,deaf people demonstrated visual function compensation in the foveal area of visual attention span when compared to reading ability–matched hearing readers.In the second study,three word–recognition experiments were carried out to explore the spatial scope in which deaf readers’ visual compensation could occur.Experiments 4 and 5combined the parafoveal priming paradigm and Flanker paradigm with the lexical decision task,respectively,and manipulated the distance between parafoveal repeated priming words/irrelevant distractor words and foveal target words（1.5°,3°,4.5°）,to investigate the influence of the parafoveal visual function compensation on foveal word recognition process from two sides of the "double–edged sword." Following that,in Experiment 6,eye–tracking technology was used to more precisely manipulate viewing angles;moreover,unrelated word priming,repeated word priming,and no priming conditions were established,allowing Experiment 6 to analyze the facilitation and interference effects of parafoveal stimulation at the same time.In other words,comparing the size of parafoveal repeated priming effect and interference effect at different visual angles to estimate the spatial scope of deaf readers’ visual compensation.Results of priming effects: In Experiments 4 and 6,there was no difference between deaf and hearing readers,and visual angles had little effect on group comparisons.Results of distract effect:Experiment 5 discovered that the distract effect size of deaf readers was greater than that of the age–matched group,but not different from that of the reading ability–matched group.What’s more,differences between deaf and the age–matched groups were most noticeable at 3° and 4.5°.However,Experiment 6 found that after controlling the location and duration of irrelevant words,the distract effect size of deaf readers was smaller than that of the reading ability–matched group and had no difference with the age–matched group.Furthermore,visual angles had little impact on differences between groups.As a result,the second study found no evidence of parafoveal visual function compensation in deaf readers during word recognition.The third study employed a sentence reading task to see if deaf readers’ parafoveal visual function compensation may improve their foveal word processing.Experiment 7 adopted the boundary paradigm and manipulated the relationship between the foveal target word N and the parafoveal preview word N+1.Target word N and preview word N+1 might be the same（repeated word preview）or irrelevant（unrelated word preview）.The parafoveal–on–foveal repetition effect refers to the difference in fixation duration of target word N between repeated and unrelated word preview conditions.During Chinese sentence reading,the parafoveal–on–foveal repetition effect was observed in deaf and reading ability–matched hearing readers.And the effect was observed in early eye movement measure（gaze duration）in deaf readers,but it emerged in late eye movement measure（total reading time）in reading ability–matched hearing readers.Consequently,the parafoveal–on–foveal repetition effect occurred earlier in deaf readers than in hearing readers with comparable reading skills,implying the existence of parafoveal visual function compensation in deaf individuals.To summarize the three studies mentioned above,this paper draws the following conclusions:（1）When processing multiple different visual stimuli at the same time,deaf people’s ability to distinguish foveal stimuli（numbers and low–complexity Chinese characters）was no different from that of age–matched hearing readers but higher than that of hearing readers with comparable reading levels.Thus,deaf readers’ visual compensation was found in the foveal region of visual attention span.（2）Repeated words in the parafoveal visual field could facilitate the recognition of foveal target words,but unrelated words in the parafoveal visual field could distract the judgment of target words.Parafoveal repetition priming effects did not differ between deaf and hearing readers,while parafoveal distract effects were smaller in deaf people than in the reading ability–matched group and no different from the age–matched group.Hence,there was no evidence of visual function compensation in deaf readers’ word recognition.（3）During Chinese sentence reading,the parafoveal–on–foveal repetition effect was found in deaf and reading ability–matched hearing readers.And the effect appeared earlier in deaf individuals than in the reading ability–matched group,indicating that parafoveal visual function compensation in deaf people could accelerate their foveal word identification.To summarize,deaf individuals can allocate more visual attention resources to the foveal or parafoveal visual fields according to the requirements of visual tasks.This enables deaf persons’ visual function compensation may occur in the fovea or parafovea.