2008 - Dye, Hauser & Bavelier
2008 - Dye, Hauser & Bavelier
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reported no differences between deaf and hearing college students on a Parasnis, Samar, and Berent (2003) administered another version of
range of tests of visuo-motor tasks, including the Rey-Osterrieth Complex CPT-called the Test of Variables of Attention (T.O.V.A., Leark, Dupuy,
Figure Test (Osterrieth, 1944; Rey, 1941) and the Wechsler Memory Scale Greenberg, Corman, & Kindschi, 1999)-to deaf and hearing college stu-
Visual Reproduction subtest (Wechsler, 1997). dents. ln the T.0.V.A., targets and nontargets are randomly presented to
Recently, deficits in continuous performance tasks (CPTs) have been observers in quick succession, and they are asked to respond to the targets
reported in deaf children (Mitchell & Quittner, 1996; Quittner, Smith, Os- only. Their data suggested that deaf observers had increased impulsiv-
berger, Mitchell, & Katz, 1994; Quittner, Leibach, & Mareie!, 2004; Smith, ity when selecting the appropriate response, accompanied by decreased
scien
Quittner, Osberger, & Miyamoto, 1998). Continuous performance tasks are perceptual sensitivity (i.e., they found it harder to distinguish between
inter
computerized measures of attention that typically require children to sus- targets and nontargets). Parasnis et ai. argued that both of these factors
contl
tain their attention to a rapidly changing visual display and make responses contributed to the apparent increased impulsivity in deaf samples, but
ing a that both reflect adaptations to the environment and not attentional pathol-
to targets while withholding responses to nontargets. ln one commonly
unde used CPT, the Gordon Diagnostic System (Gordon & Mettleman, 1987), ogy. Specifically, a less conservative response selection reflects a reliance
in le digits appear one at a time in rapid succession in the center of a display- upon vision for alerting in the absence of auditory input. ln the absence of
on r children are usually required to make a response to a target number when it auditory cues to objects and events in the environment, more reliance is
expe is preceded by a specific number, but not otherwise. For example, children placed upon visual information for bringing such objects and events to the
cogr may be asked to press the response button upon seeing the target number 9 attention ofthe deaf observer. The decreased perceptual sensitivity in cen-
uniq if it has been preceded by the number 1, but not otherwise. ln this case, the tral vision, they argue, results from redistribution of attention away from
learr' sequence 1-9 would require a response to the 9, whereas the sequence 4-9 the center and toward peripheral vision, as initially proposed by Neville
for<· would require the child to withhold a response to the 9 and the sequence and her collaborators (Neville; Schmidt, & Kutas, 1983; Neville & Lawson,
ily ( 1-4 would require the child not to make an impulsive response on the 1978a,b). This possibility was also considered by Mitchell and Quittner
psyc basis of seeing the number 1 alone. (1996) in regard to their findings on distractibility. This idea, that a redis-
ed0t Severa! different versions of this CPT have been used with deaf chil- tribution of attention occurs across visual space in deaf individuais, is the
deaf; dren. ln one version, a delay task, children are required to press a button focus of the next section. However, before considering that hypothesis, it
in e~ and then wait before pressing it again in the absence of any numerical is important to consider other limitations in the work just reviewed, with
stimuli. If they wait long enough, they receive a reward (a point), providing a particular focus upon the selection of appropriate stimuli and careful
fun<'
a measure of the efficiency with which children obtain rewards, taken to consideration of what is meant by a "deaf child" in the context of such
solv
be an índex of impulsivity. ln a second version, a vigilance task, correctly studies.
pressing the button to a 9 preceded by a 1 is an índex of vigilance or sus-
tained attention, whereas pushing the button at any other time (a commis-
sion error) is taken as a measure of impulsivity. A third version of CPT, a The lmportance of Etiology and Communication
distractibility task, involves irrelevant numbers appearing to the ]eft and
right of the central numbers. Poor performance is attributed to the child Lesser and Easser (1972) suggested that the impulsivity that had been re-
being distracted by the flanking numbers. Using these tasks, deaf children ported in early studies of behavior problems in deaf children might have
este have been reported to be more impulsive (Quittner et ai., 1994) and to suf- been a result of a lack of self-regulation stemming from difficulties in
Ce1 fer from increased distractibility (Mitchell & Quittner, 1996). Furthermore, communicatiorr and expressing needs. Thus, early on, the importance of
aise Smith et aL (1998) reported data suggesting that cochlear implants (Cls) language in the development of attentional skills had been acknowledged
of diminish the strength of these deficits, although the children with Cls did (see Hauser, Lukomski, & Hillman, this volume). Furthermore, Meadow
anC not achieve the performance leveis of hearing controls. The authors suggest (1980) cited a study by Chess, Korn, and Fernandez (1971) that showed
of. that their data indicate a deficit in visual selective attention stemming from that maternal rubella was related to hyperactivity, thus establishing the
ind poor multimodal sensory integration as a result of early, profound hearing importance of examining comorbidity in deaf children. That is, many deaf
is i loss. Such a position can be termed a deficiency hypothesis and, generally children have learning and other disabilities, in addition to their hearing
vel stated, it proposes that integration of information from the different senses losses, that are often associated with the sarne etiological cause. Indeed,
rei; is an essential component to the development of normal attentional func- deaf individuais in general vary greatly in the etiology of their deafness, its
tioning within each individual sensory modality. severity, and age of onset.
' 111
Over 20 million people in the United States have been diagnosed demonstrates increased sensitivity to that object. An early study by Loke
with hearing loss, representing a prevalence ~ate of 9% (Ries, 1994). The and Song (1991) demonstrated that deaf observers responded more rapidly
etiology of hearing loss can be hereditary (-50%) or acquired by severa! to targets flashed at locations in the periphery, a finding replicated recently
mechanisms such as prenatal or perinatal infections (cytomegalovirus, ru- by Chen, Zhang, and Zhou (2006). lmportantly, in these studies, the loca-
bella, and herpes simplex), postnatal infections (meningitis). premature tion of the peripheral target is unpredictable (i.e., they do not a!ways ap-
birth, anoxia, trauma, or as a result of ototoxic drugs administered during pear at the sarne peripheral location). and the targets are presented for brief
pregnancy. Many of these causes have been associated with other, some- durations so that the observer cannot make a visual saccade and redirect
times severe, neurological sequelae that affect behavioral, cognitive, and their fixation to the target !ocation. The conclusion, therefore, is that the
psychosocial functioning (Hauser, Wills, & Isquith, 2006; King, Hauser, & deaf observers had allocated more of their attention to the whole of the
Isquith, 2006). Hereditary deafness is associated with over 350 genetic con- peripheral field prior to the onset of the target.
ditions (Martini, Mazzoli, & Kimberling, 1997), and about a third of these Another common technique for analyzing how attention is distributed
genetic conditions are associated with syndromes (Petit, 1996). Although across the visual field is the fl.anker compatibility paradigm. ln this para-
not ali hereditary cases of deafness are nonsyndromic, hereditary-deafened digm, participants are required to identify a target (usually presented at fix-
individuais are more likely to have unremarkable neurological and psychi- ation in the center of a screen). The decision is typically a two-alternative
atric histories. forced choice, using stimuli such as shapes (square or diamond). letters
ln the United States, many individuals who have severe to profound (H or S). or arrows (+- or -t). Accompanying the target are peripheral dis-
hearing loss before the age of 3 years use American Sign Language (ASL) as tractors, located at varying degrees of visual angle (usually to the left and
their first language, and thus may also be less likely to have self-regulatory right ofthe target). These distractors can be congruent with the target (e.g.,
issues resulting from communicative stress and an inability to express square target and square distractors) cir incongruent (e.g., square target
themse!ves. This group relies on visual routes to learning and language and diamond distractors). By measuring how long it takes an observer to
access, and has similar values, beliefs, and behaviors that usually reflect respond accurately to the target and how many mistakes they make, the
Deaf culture. The community of ASL users is often referred to in the litera- degree of processing of the distractors can be measured. Typically, congru-
ture as a linguistic minority community because of the similarities it has ent distractors will speed responses (or have !ittle effect). whereas incon-
with other minority communities in terms of language and culture (Ladd, gruent distractors will slow down responses and lead to more errors. The
2003; Padden & Humphries, 2005). The body of research considered next more attention that an observer allocates to peripheral vision, the greater
has focused largely upon such deaf individuais, often referred to as deaf their sensitivity to the distractors, and the greater the influence of those
native signers, minimizing potential confounds due to comorbid disorders distractors on response times and errors. Although this greater influence
or difficulties and problems stemming from communication problems in can be considered as a sign of greater distractibility, fundamentally it re-
early childhood. flects greater processing resources allocated to the distractors.
ln a task employing a flanker compatibility paradigm, enhanced pro-
cessing of peripheral distractors located at 4.2 degrees of visual angle from
Altered Distribution of Visual Attention a concurrent target has been reported for deaf native signers relative to hear-
in Deaf Individuais: Behavioral Studies ing participants (Proksch & Bavelier, 2002). ln this experiment, participants
were asked to identify shapes positioned in a circular pattern around fixa-
In contrast to studies reporting examples of visual deficits, studies using tion, while ignoring distractors placed peripherally to the circular pattern.
homogenous samples of deaf native signers have demonstrated changes in The proposal that deaf individuais have greater attentional resources in the
visual function that could be considered more adaptive, in that they show periphery predicts that peripherally located distractors will receive more
a compensation in the visual modality for the lack of auditory input. ln attentional resources and thus be more distracting for deaf than for hearing
such individuals, a selective enhancement for stimuli that are peripheral individuais. This peripheral condition was contrasted with a condition in
or in motion and require attentional selection has been demonstrated using which the distractor was presented centrally. Results confirmed the known
a variety of paradigms. finding that, in hearing individuais, central distractors are more distract-
One of the key attributes of attention is that, when allocated to a posi- ing than peripheral distractors. ln contrast, deaf individuals were more
tion in space, an object occupying that space receives enhanced process- distracted by peripheral distractors than were hearing individuais, and,
ing. Put another way, when attention is allocated to an object, an observer interestingly, less so by central distractors.
256 Deaf Cognition Deafness and Visual Attention 257
These findings establish that, whereas in hearing individuais atten- In contrast to these changes invisual attention, in which the onset and
tion is at its peak in the center of the visual field, deaf individuais show location of stimuli are unknown, attempts to demonstrate changes in basic
greater attention at peripheral locations. Subsequently, Sladen et al. (2005) visual skills arnong deaf native signers using psychophysical methods and
confirmed greater processing of peripheral distractors in deaf individuais (where target location and onset are known a priori) have been unsuccess- 1
Ula-
by showing that the responses of deaf individuals were more influenced ful. For exarnple, in a task measuring contrast sensitivity thresholds across >oth
by distractor letters positioned at -1.5 degrees from a letter target than different spatial frequencies, temporal frequencies, and spatial locations,
evi-
were hearing controls. Following the sarne logic, Dye, Baril, and Bavelier Finney, Fine, and Dobkins (2001a) reported no differences between deaf
'.>eaf
(2007) recently showed that nonletter distractors (arrows) positioned at and hearing individuais. An absence of overall population effects has also
·arch
increasing eccentricities (1.0, 2.0, and 3.0 degrees) increasingly affected been found in measures ofvisual flicker (Bross & Sauerwein, 1980), bright-
target performance in deaf individuais as compared with hearing individ- ness discrimination (Bross, 1979), and temporal discrimination (Mills,
uais. Finally, using peripheral kinetic and foveal static perimetry-where 1985; Poizner & Tallal, 1987). Even psychophysical thresholds for motion
observers are asked to respond when they can see a moving or static light processing have been found to be equivalent in deaf and hearing individu- JSY-
point, respectively-deaf individuais were reported to be better than hear- als. Sensitivity for motion direction and for small changes in motion veloc- clies
ing controls at detecting moving lights in the periphery, manifested as a ity was compared in deaf native signers and hearing individuais, and no and
difference in field of view (Stevens & Neville, 2006). No difference was detectable difference was reported (Bosworth & Dobkins, 2002a,b; Brozin- .ical
observed in their sensitivity to static points of light presented in central sky & Bavelier, 2004). This lack of effect stands in contrast to other studies, : of
vision. What all of these "compensation" studies have in common is that such as the kinetic perimetry study mentioned earlier, which document the
they focus upon visual attention skills-how the deaf individuais allocate enhanced processing of motion information in deaf naÜve signers when 1det
limited processing resources to the visual scene--and report enhanced at- presented under conditions of attention. 1ter
tention to the periphery for deaf native signers across a range of visual The sarne dissociation between attentional changes but little to no His
angles (from 1.5 to over 60 degrees). perceptual change has been observed in the domain of touch: deaf indi- Jng
In the previous literature, this greater peripheral processing has often viduais have been shown to have equivalent thresholds for detecting dif- ent.
been interpreted as greater distractibility in deaf individuais. Here, we ferences in vibration frequency, but a superior ability to detecta change in . to
argue that it is better understood as a difference in allocation of atten- vibration frequency under conditions of attention, when the time of onset 1cy,
tional resources between deaf and hearing observers, with enhanced pe- of the change in vibration is unknown (Levanen & Harndorf, 2001). One
ons
ripheral processing in deaf people and enhanced central processing in working hypothesis is that a sensory loss leads to changes in higher-level
eu-
hearing people. This view predicts that deaf individuais should be more attentional processing, especially i:íi) domains in which information .from
distracted by irrelevant peripheral information, but hearing individuais multiple senses is integrated (Bave~er, Dye, & Hauser, 2006; Baveher &
should be more distracted by irrelevant central information. Accordingly, Neville, 2002). It thus appears that early deafness results in a redistribution
in tasks where the target is slightly off-center, deaf individuais are more of attentional r!lsources to the periphery, most commonly observed when
distracted by peripheral distractors but hearing individuais by central input from peripheral and central space competes for privileged access to
distractors (Proksch & Bavelier, 2002). In terms of adaptation to the en- processing resources. 1ers
vironment, the attentional change observed in deaf individuais makes in- ; in
tuitive sense--a redistribution of visual attention to the periphery can mal
·ork
compensate for the lack of peripheral auditory cues provided by the en- Altered Distribution of Visual Attention trai
vironment, such as the sound of an approaching vehicle or the creak of in Deaf Individuais: lmaging Studies ue).
an opening door. ced
Importantly, such enhanced peripheral attention has been observed in Given the observed changes in the distribution of visual attention that 'of
deaf signers, but not in hearing individuais who are native signers (Bavelier have been observed behaviorally arnong deaf native signers, it makes sense ices
et ai., 2001; Neville and Lawson, 1987c; Proksch and Bavelier, 2002). The to ask whether we can observe associated neurological changes. There is sity
lack of a similar effect in hearing native signers demonstrates that using now a substantial body of work looking at compensational changes in brain
a visuo-manual signed language such as ASL is not sufficient to induce activation following early auditory deprivation. One well-studied brain
changes in peripheral attention. Rather, deafness appears to be the leading area is the medial temporal area/medial superior temporal area (MT/
factor in this reorganization of the attentional system. MST], an area of visual cortex involved in the detection and analysis of
258 Deaf Cognition
Deafness and Visual Attention 259
movement. When viewing unattended moving stimuli, deaf and hearing attributions, as opposed to a state of inattentiveness and attentional pa-
individuais do not differ in the amount of activation in MT/MST cortex. thology per se. With respect to attentional allocation, problems may arise
However, when required to attend to peripheral movement and ignore when there is a conflict between the demands of the environment and the
concurrent central motion, enhanced recruitment of MT/MST is observed default allocation of resources. For example, in structured learning envi-
in deaf native signers as compared with hearing contrais (Bavelier et ai., ronments, such as classrooms, a deaf child's attention has to be focused
] 2000, 2001; Fine, Finney, Boynton, & Dobkins, 2005). This pattern echoes a upon an instructor or an interpreter. When sources of visual distraction
general trend in the literature, whereby the greatest population differences occur in the periphery, a deaf child may appear to be inattentive, as their
have been reported for motion stimuli in the visual periphery under condi- attention is constantly being drawn toward those peripheral events. Note,
tions that engage selective attention, such as when the location or time of however, that in other environments such an adaptation in resource allo-
arrival of the stimulus is unknown or when the stimulus has to be selected cation may be beneficial. For example, a research report published by the
i from among distractors (Bavelier et ai., 2006). California Department of Motor Vehicles suggested that deaf drivers had
il There are severa! potential ways in which cross-modal reorganization driving records the sarne as or better than hearing drivers,' and the ability
;I could support the changes observed in the spatial distribution of visual to better process peripheral information may also confer certain advan-
attention in deaf individuais. One possibility is that an expansion occurs tages in team sports (Knudson & Kluka, 1997), al_though reports to date are
in the representation of the peripheral visual field in early visual cortex. only anecdotal.2
However, currently, little data supports this hypothesis (Fine et ai., 2005). The concern, here, is with Iearning environments and how best to con-
Another possibility is that, in deaf individuais, multimodal associative struct Iearning environments in which deaf children are less distracted by
cortex-parts of the brain that combine information from different sen- events in the periphery, allowing them to focus their resources upon the
sory modalities-may display a greater sensitivity to input from remaining task at hand. The behavioral research cited here suggests that deaf individ-
modalities such as vision and touch. Evidence for this hypothesis comes uais cannot help but be distracted by visual information in their peripheral
from studies reporting changes in the posterior parietal cortex of deaf in- vision. This is perhaps unintuitive for the hearing reader, who experiences
dividuais (Bavelier et ai., 2000, 2001), an area known to be involved in the distraction more commonly from visual input in the center of their visual
integration of information from different sensory modalities. Finally, it is field. Imagine your frustration, for example, if every word on this page
possible that in deaf individuais the Jack of input from audition causes were to change calor as soon as you fixated upon it. But for the deaf indi-
the auditory cortex-which is multimodal in nature-to reorganize and vidual, inattention may occur more easily as a result of visual activity that
process visual information. Indeed, there is some evidence that auditory is away from the direction of their overt gaze. It is not that they are being
areas in the superior temporal sulcus show greater recruitment in deaf than inattentive toward what they are looking at directly, but rather that they
in hearing individuais for visual, tactile, and signed input (Bavelier et ai., cannot help but allow peripheral input to draw their covert attention away
2001; Finney, Fine, & Dobkins, 2001b; Finney, Clementz, Hickok, & Dob- from the task at hand, in much the sarne way that hearing individuais can-
kins, 2003; Levanen, Jousmaki, & Hari, 1998; Neville et ai., 1998). not help but be distracted by central distractors.
To conclude, behavioral studies suggest that a redistribution of at- Any modification of the learning environment that aims to counteract
tentional resources occurs in deaf individuais, with an enhancement of these sources of visual distraction must also be sensitive to the psychologi-
peripheral space that can be accompanied by a reduction at competing cal and cultural needs of the deaf child. It appears that the change observed
central locations. These b.ehavioral differences are accompanied by neural in their attentional system is an adaptive change-it allows them to adapt
changes suggesting cross-modal reorganization in areas that integrate infor- to their environment, given the Jack of an auditory sense to inform them
mation from different modalities and possible recruitment of multimodal about the environment and guide the focus of their attention. Thus, po-
cortex in auditory regions for the processing of visual information. sitioning a deaf child at the front of the classroom with their classmates
behind them, or in a position where they cannot see out of windows or
Ladd, N. P. (2003). ln search of deafhood. Clevedon, U.K.: Multilingual Matters. Osterrieth, P. A. (1944). Le test de copie d'une figure complex: Contribution a
Larr, A. L. (1956). Perceptual and conceptual abi!ity ofresidential school deaf l'etude de la perception et de la memoire [The test of copying a complex
children. Exceptiona/ Children, 23, 63-66, 88. figure: A contribution to the study ofperception and memory]. Archives