The Association Between Visual,
Nonverbal Cognitive Abilities and Speech,
Phonological Processing, Vocabulary and Reading
Outcomes in Children With Cochlear Implants
Lindsey Edwards and Sara Anderson
Objective: The aim of this study was to explore the possibility that
specific nonverbal, visual cognitive abilities may be associated with
outcomes after pediatric cochlear implantation. The study therefore
examined the relationship between visual sequential memory span and
visual sequential reasoning ability, and a range of speech, phonological
processing, vocabulary knowledge, and reading outcomes in children
with cochlear implants.
deafness, including global developmental delay, cerebral palsy
or autistic spectrum disorder, which may be known preimplantation (e.g., Meinzen-Derr et al. 2010). However, many additional
difficulties that are not apparent before the child has received
cochlear implants, are more subtle, or emerge gradually as the
child matures. For example, specific learning disabilities such
as language disorders or dyslexia cannot be identified in very
young deaf children; their diagnosis is typically not achieved
until much later than in hearing children. To add to the complexity, some children make poor progress in developing speech,
language and literacy skills after cochlear implantation for no
readily identifiable reason. In this case factors such as the nature
of the child’s language-learning environment and parent/carer
interactions with the child are likely to be contributory factors.
Thus there is a pressing need to improve our knowledge and
understanding of the factors that are predictive of outcome or
benefit, and translate these into individualized assessment and
intervention strategies to achieve optimal cognitive and linguistic development.
One area of research that is showing considerable promise
in meeting this need has focused on describing, understanding,
and explaining the neurocognitive or information-processing
variables that contribute to individual differences in outcomes
and benefit (e.g., Fagan et al. 2007; Pisoni, et al. 2010). Furthermore, as Pisoni et al. (2008) state “while some proportion of the
variance in performance is associated with peripheral factors
related to the audibility and the initial sensory encoding of the
speech signal into information-bearing sensory channels in the
auditory nerve, several additional sources of variance are associated with more central cognitive and linguistic factors that are
related to perception, attention, learning, memory and cognitive
control.”
Some further clues as to the cognitive processes that may be
relevant in accounting for the variability in speech, language,
and literacy outcomes can be drawn from a range of related
lines of research, which will now be briefly considered.
Design: A cross-sectional, correlational design was used. Sixty-six children aged 5 to 12 years completed tests of visual memory span and
visual sequential reasoning, along with tests of speech intelligibility, phonological processing, vocabulary knowledge, and word reading ability
(the outcome variables). Auditory memory span was also assessed, and
its relationship with the other variables examined.
Results: Significant, positive correlations were found between the visual
memory and reasoning tests, and each of the outcome variables. A series
of regression analyses then revealed that for all the outcome variables,
after variance attributable to the age at implantation was accounted for,
visual memory span and visual sequential reasoning ability together
accounted for significantly more variance (up to 25%) in each outcome
measure.
Conclusions: These findings have both clinical and theoretical implications. Clinically, the findings may help improve the identification of children at risk of poor progress after implantation earlier than has been
possible to date as the nonverbal tests can be administered to children
as young as 2 years of age. The results may also contribute to the identification of children with specific learning or language difficulties as well
as improve our ability to develop intervention strategies for individual
children based on their specific cognitive processing strengths or difficulties. Theoretically, these results contribute to the growing body
of knowledge about learning and development in deaf children with
cochlear implants.
Key words: Children, Cochlear implant, Nonverbal, cognitive, Outcomes.
(Ear & Hearing 2014;XX;00–00)
INTRODUCTION
All parents who choose cochlear implantation for their deaf
child are informed that the degree of benefit cannot be precisely
predicted. Although some factors have been reliably associated
with speech and language outcomes and literacy achievements,
for example, age at implantation, length of auditory deprivation,
and early linguistic experience (auditory–oral versus total communication), there remains a large degree of variability in outcome (e.g., Marschark et al. 2007; Archbold et al. 2008; Geers
et al. 2008; Lyxell et al. 2009). Some of this variability can be
accounted for by factors such as disabilities in addition to the
Phonological Processing, Verbal Memory Capacity, and
Reading in Hearing Children
First, in hearing children, strong associations are found
between verbal (working) memory capacity and phonological processing skills, and specific reading difficulties. Verbal
memory capacity refers to the amount of information that can
be stored and “manipulated” in some way, over a short period
of time (i.e., seconds). Verbal memory capacity is typically
assessed using a digit span task giving a measure of auditory
memory span, and deficits on this and other tests of verbal
Great Ormond Street Hospital for Children, London, England, United
Kingdom.
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EDWARDS AND ANDERSON / EAR & HEARING, VOL. XX, NO. X, XXX–XXX
short-term memory have consistently been found in children
with specific reading disorders (e.g., Gottardo et al. 1996; de
Jong 1998; Helland & Asbjørnsen 2004; Kibby et al. 2004).
One task commonly used to assess phonological processing
skills is the nonword repetition task, which tests the ability to
assemble, rehearse, and produce novel phonological sequences
from short-term memory. A number of studies have found a
strong association between deficits in nonword repetition and
both specific language impairment and reading difficulties (e.g.,
Bishop et al. 1996; Catts et al. 2005; Conti-Ramsden & Durkin
2007; Rispens & Parigger 2010).
Phonological Processing and Reading in Deaf Children
Second, in children with a hearing loss, with or without
cochlear implants, phonological processing skills are typically
weak compared with those of hearing peers. These skills have
been associated with a range of speech, language, and literacy
outcomes. For example, Dillon and Pisoni (2006) tested nonword repetition in 76 children with cochlear implants aged
7 to 9 years. They found strong associations between nonword
repetition and three measures of reading outcome (nonword
reading, single word reading, and reading comprehension).
These correlations remained significant when age at onset of
deafness, communication mode, and performance intelligence
quotient (IQ) were controlled for. Carter et al. (2002) also used
a nonword repetition task to examine prosodic representations
of words. They found that 8- to 10-year olds, who had been
using their cochlear implant for a mean of 5 years, only correctly
imitated 5% of the nonwords. However, 64% of the imitations
contained the correct number of syllables. They also found that
the syllable score was significantly positively correlated with
language comprehension and speech intelligibility. Recently,
Casserly and Pisoni (2013) demonstrated that the performance
of 8- to 10-year old cochlear implant users on a nonword repetition task was predictive of measures of speech and language at
the age of 16 to 18 years, including speech intelligibility, receptive vocabulary, and reading ability.
In another early study Dyer et al. (2003) assessed phonological awareness and decoding skills along with rapid automatized
naming of visual material, in 49 deaf students with a mean age
of 13 years but whose mean reading age was 7 years. Phonological awareness and decoding skills were poorer in these deaf
children compared with hearing children matched for reading
(not chronological) age and correlated significantly with reading delay on the rhyme-awareness task. In addition two recent
studies have also examined phonological awareness or processing skills and reading in children and adolescents with cochlear
implants. Geers and Hayes (2010) reported that phonological
processing skills accounted for an additional 19% of the variance in literacy achievement after factors such as sex, duration
of deafness, performance IQ, and family characteristics were
taken into account. Similarly, Johnson and Goswami (2010)
found that reading attainment was significantly correlated with
phonological awareness in 5- to 15-year olds with cochlear
implants, when age and nonverbal IQ were controlled for.
Memory and Reading in Deaf Children
In a third line of research (but sometimes within the same
studies as described earlier in the article), the relationships
between memory capacity, working memory and speech,
language and reading skills have been explored, again both
in deaf children with cochlear implants and those using conventional hearing aids. Johnson and Goswami (2010) used
a forward digit span task to assess auditory memory, and the
Leiter-R (Roid & Miller 1997) memory screen to assess visual
memory in implanted children. They found that visual memory
was not correlated with the phonological awareness tasks, but
was with reading comprehension. Auditory memory was linked
to phonological awareness, receptive and expressive vocabulary
knowledge, reading accuracy and comprehension, along with
speech intelligibility. In a longitudinal analysis with a large
sample of cochlear implant users, Pisoni et al. (2011) examined
the predictive relationships between auditory memory capacity (digit span) at age 8 to 9 years, and speech intelligibility,
vocabulary knowledge, language ability, and reading ability
at around 16 years of age. They found strong positive correlations between longest digit span at age 8 to 9 years and all
the speech and language outcome measures in adolescence.
However, interestingly from a theoretical perspective, backward
digit span, which is considered a measure of auditory working memory (verbal memory capacity when concurrent mental
processing is required) rather than simply auditory immediate
memory capacity (rote sequential serial item memory), correlated significantly with tests of higher-order language functioning, but not speech perception or recognition measures. Pisoni
et al. suggested that this dissociation between the forward and
backward digit span results may indicate that rapid phonological encoding and immediate verbal-sequential phonological
memory are essential building blocks for the development of
good speech perception and speech-language skills. In addition, good verbal-sequential memory abilities are needed for
all higher language processing tasks involving encoding, storing, and maintaining representations of speech sounds, spoken
words, and sentence meanings in working memory.
Visual–Spatial Memory and Reading in
Hearing Children
While it makes intuitive sense that normal auditory–verbal
memory skills are important for the effective development of
spoken language and later literacy skills, it is less clear whether
visual memory abilities would also be expected to play a significant role, either in hearing children or those with a hearing loss.
Therefore it is perhaps unsurprising that there is considerably
less research exploring this question. Thus the next piece in this
puzzle is the observation that it is not only the verbal memory
span that is reduced in hearing children with specific reading
disability; there is evidence that their visual–spatial memory
capacity or visual memory span and working memory are also
poorer. The findings are less consistent than for verbal memory
deficits, but the contradictory findings could be accounted for
by differences in participant inclusion criteria and the nature
of the memory tasks used (e.g., Olson & Datta 2002; Jeffries
& Everatt 2004; Kibby et al. 2004; Smith-Spark &Fisk 2007).
Menghini et al. (2011) attempted to resolve this issue by testing
children with developmental dyslexia, but no other concomitant disorders and normal intelligence, and used memory tasks
minimally demanding on attentional and executive cognitive
resources. They concluded that children with specific reading
deficits do have deficits in visual–spatial memory span, in addition to verbal memory span.
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EDWARDS AND ANDERSON / EAR & HEARING, VOL. XX, NO. X, XXX–XXX
Visual Memory and Reading in Deaf Children
There is some evidence that short-term memory span for
visually presented stimuli is poorer in deaf children, including
those with cochlear implants, than in their hearing peers. Khan
et al. (2005) found a significant difference between deaf and
hearing children in visual memory span for pictures of common
objects presented in an array, where the child had to point to the
pictures in the same order as that given by the examiner (Forward
Memory subtest from the Leiter-R). However, there was no difference between the hearing children and children who had been
using their cochlear implant for 1 year. A novel visual memory
span task was developed by Cleary and colleagues based on the
Simon memory game, where the task is for the child to reproduce sequences of presentations of colored lights. The authors
conducted a series of experiments with children with cochlear
implants and found that these children had shorter memory
spans and poorer sequence learning when the same patterns were
repeated, again in comparison with hearing peers (Cleary et al.
2001, 2000; Pisoni & Cleary 2004). These authors suggest that
individual differences in outcome in deaf children who receive
cochlear implants “may reflect fundamental learning processes
that affect the encoding and retention of temporal information in
both short- and long-term memory” (Pisoni et al. 2008, p. 77).
Studies that report findings on visual memory span and reading ability in deaf children are equally scarce. However, two
studies provide some relevant results. Harris and Moreno (2004)
used pictures of objects that were visually similar, had similar
sounding names, and were formed with similar hand shapes in
British Sign Language or dissimilar in these three respects. Pictures were presented in increasingly long sequences, and the
child had to name the objects in the order in which they had
appeared. In deaf children aged 14 years (but not in the group
aged 8 years), visual memory span was a significant predictor of reading performance when age and nonverbal IQ were
accounted for. It is interesting to note that in these older children recall span was not affected by the similarity of the sounds
of the objects’ names, suggesting the children were not using
phonological coding when remembering items. Clearly, in this
task although the stimuli are presented visually they are verbally encoded (as the child had to name each object), and the
response mode is also verbal.
Using essentially the same type of task, but with pictures of
words varying in number of syllables, Kyle and Harris (2006)
found no correlation between visual memory span and a number
of measures including expressive vocabulary, reading, or spelling. However, these children were younger (aged 7 to 8 years),
suggesting that there may be a developmental progression
involved in the relative contributions of auditory compared with
visual information processing in the acquisition of reading skills.
Visual Sequential Reasoning Abilities in Deaf Children
The next question is whether the difficulty with auditory
memory span, which relies on the processing of sequentially
presented auditory information, is reflective of a wider difficulty in processing or understanding sequential information,
that is, do hearing children with reading difficulties and deaf
children also have problems with reasoning or problem solving
with nonverbal or visual information that is sequential? To our
knowledge no studies have addressed this directly in hearing
or deaf children. However, Khan et al. (2005) did report that
a group of very young (aged 2 to 5 years) deaf children performed significantly worse on the Sequential Order subtest of
the Leiter-R compared with their hearing peers.
To summarize, previous research has suggested that reading
competence (or conversely reading deficit) is dependent on phonological processing skills, which in turn is strongly associated
with verbal memory capacity, and possibly also visual memory
capacity. Deaf children are at risk of experiencing significant
difficulties in developing phonological awareness and processing skills, and have deficits in verbal and visual memory, as
well as possibly visual reasoning problems. However, to date,
no empirical studies have examined the relationships between
the combination of visual memory span, visual, nonverbal
reasoning skills, speech intelligibility, phonological processing, language and reading outcomes in children with a hearing
loss or deaf children with cochlear implants. Given the studies
described earlier in this article, it seems plausible that such a
relationship may exist.
The Present Study—Aims and Rationale
As outlined at the beginning of the Introduction, one of the
major challenges for clinicians working with children with
cochlear implants is identifying those at risk of poor progress,
or those who have specific learning difficulties in addition to
those arising from their deafness, as early as possible. However,
most tests conventionally used to assess specific learning disorders require a minimum level of spoken language production or
comprehension for their administration. This typically excludes
those very children for whom the need to establish what is preventing progress is greatest. It would be of immense value if
there were reliable and valid visual, nonverbal tests of neurocognitive processes that were predictive of speech, phonological processing, reading and language outcomes in children with
cochlear implants, particularly if they could be administered to
very young deaf children.
Thus the primary aim of this study is to establish whether
there are links between visual (sequential) memory span, visual
sequential reasoning ability, and speech intelligibility, phonological processing, reading and vocabulary knowledge in children with cochlear implants. In this study we used phonological
processing as an outcome (dependent) variable, along with
reading and vocabulary knowledge (as an indicator of language
TABLE 1. Participant characteristics
Male: Female
Mean age at testing (SD; range)
Mean age at (1st) implant (SD; range)
Duration of (1st) implant use (SD; range)
Etiology of deafness
Unknown
Genetic (nonsyndromal)
Syndromal
Meningitis
Rubella/cytomegalovirus infection
Meningitis
Communication mode
Speech
Speech and sign
Sign
32: 34
8.5 yrs (1.9; 5.4–11.7)
3.7 yrs (1.5; 1.2–8.9)
5.13 yrs (2.0; 1.0–10.1)
39%
21%
15%
17%
6%
2%
80%
14%
6%
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EDWARDS AND ANDERSON / EAR & HEARING, VOL. XX, NO. X, XXX–XXX
development) rather than as an explanatory (independent) variable. We have focused on sequential visual cognitive processes
or abilities because language is essentially sequentially based
(phonemes need to be produced in the correct sequence in
words, words in the right order in sentences to be grammatically correct). Therefore the ability to process sequential visual
information may be hypothesized to be associated with the ability to process auditory sequential information, and thus with the
development of phonological, language, and literacy abilities.
There are a number of possible models of the relationships
between all these factors that could be tested, for example, hierarchical models where variables are included incrementally
in several steps. However, we sought to test the most simple
models, and include as few variables as possible as to account
for the variability in outcomes after cochlear implantation, specifically focusing on nonverbal, visual measures. This was in an
attempt to maximize the clinical interpretability and value of
the results. In particular, we wanted to use those tests that can
potentially be administered to children before the emergence of
assessable spoken language skills. However, auditory memory
capacity (digit span) was also assessed and used as an explanatory variable because this test is probably the simplest auditory/
verbal one for deaf children to tackle, as it only requires the
ability to articulate the numbers one to nine in a sufficiently
clear manner for the examiner to be able to recognize them.
Furthermore, digit span has received the most attention in previous research and it is highly established as a predictor of speech
intelligibility, phonological processing ability, reading and language in implanted children. This study will therefore allow us
to explore (nonstatistically) the relative strength of associations
between auditory and visual memory capacities and outcomes
after pediatric cochlear implantation, and consider our findings
in the context of previous research.
Hypothesis • Visual sequential reasoning and visual memory
span are significantly positively associated with speech intelligibility, phonological processing, vocabulary knowledge, and
reading outcomes in deaf children after cochlear implantation.
PARTICIPANTS AND METHODS
Design
The study used a cross-sectional, correlational design. The
main explanatory variables were visual memory span and visual
sequential reasoning ability. Six outcome variables were a range
of speech intelligibility, phonological processing, reading, and
vocabulary knowledge measures.
Participants
All the children aged between 5 and 12 years during a
6-month period, currently patients on our cochlear implant program, were invited to participate in the study. This was with
the exception of children with known significant developmental delay or neuro-developmental disorders such as autistic
spectrum disorder. The characteristics of the resulting sample
are summarized in Table 1. The participants were 66 children,
with approximately equal numbers of girls and boys. The cause
of deafness was unknown for around 40% of the children,
genetic (nonsyndromal) for approximately 20% and syndromal
(Waardenburgs, Pendreds, CHARGE Association, Ushers syndrome and Brachio-oto-renal syndrome) in 15%, and congenital infections or meningitis in 25%. There were no significant
differences in scores on any of the visual memory, visual reasoning, auditory memory, speech intelligibility, phonological
processing, and vocabulary or reading tests when the children
were divided into three groups according to etiology (unknown,
genetic, or syndromic/infection/prematurity).
All but 1 child was congenitally deaf or deafened before
their second birthday. The preimplant pure-tone average aided
loss for 2 and 4 kHz in the worse ear was greater than 90 dBHL.
Seven children had bilateral implants: 2 simultaneously and the
remainder sequentially. The majority of the children used spoken English as their main mode of communication, with some
also using signs to support their communication (receptively,
expressively, or in both ways). Four children had a preference
for using sign expressively, but had sufficient spoken language
skills to enable them to understand the instructions for the tests
administered for this study. English was not the first language
for the parents of 7% of the children.
Measures
Memory • Forward Memory Subtest: Leiter International Performance Scale—Revised (Leiter-R; Roid & Miller 1997). This
test assesses visual memory span by testing the child’s ability
to reproduce the sequence in which the examiner has pointed to
pictures of objects in a grid, presented at a rate of one picture
TABLE 2. Descriptive statistics for the visual sequential memory and reasoning, auditory memory, speech, phonological processing,
vocabulary and reading variables
Normalization Sample
Variable (Test)
Auditory Memory Span (CMS Numbers)
Fluid Reasoning composite (Leiter-R)
Visual Memory Span (Leiter-R)
Children’s Speech Intelligibility Measure
Phonological Processing (NEPSY II)
Repetition of NonWords (NEPSY II)
Receptive Vocabulary (TOWK)
Expressive Vocabulary (TOWK)
Word Reading (WIAT-II)
Cochlear Implant Sample
Mean (SD)
Mean (SD)
Range
% of Cochlear Implant
Children Lower Than 1 SD
Below Norm
10 (3)
100 (15)
10 (3)
N/A
10 (3)
10 (3)
10 (3)
10 (3)
100 (15)
7.17 (3.4)
104.3 (15.3)
11.9 (3.4)
69.3 (29.8)
7.61 (4.3)
10.0 (4.5)
6.8 (3.4)
7.4 (3.7)
86.5 (22.9)
1–15
67–137
2–18
0–100
1–15
1–18
3–15
3–19
40–128
56%
9%
7%
N/A
34%
22%
54%
49%
43%
CMS, Children’s Memory Scale; TOWK, Test of Word Knowledge; WIAT-II, Wechsler Individual Achievement Test–II.
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EDWARDS AND ANDERSON / EAR & HEARING, VOL. XX, NO. X, XXX–XXX
per second. Again the sequences start at two stimuli in length,
and become increasingly long. Testing is stopped after the child
has made six errors. The number of correct sequences is converted to a scaled score (mean 10, SD 3) based on hearing children norms. The test is intended for children between 2 and 16
years of age.
Numbers Forward Subtest: Children’s Memory Scale
(Cohen 1997). This is a standard digit span test of verbal memory capacity, where the child repeats back increasingly long
series of numbers presented one digit per second, starting with
two digits. There are two trials for each sequence length, and
testing is stopped once the child has failed both trials for a particular length. The number of correctly reproduced sequences is
converted to an age-based scaled score. The mean and standard
deviation of the hearing standardization sample are 10 and 3,
respectively. The test can be used for children aged between 5
and 16 years.
Visual Sequential Reasoning • Fluid Reasoning Composite:
Leiter-R. Individual subtests from the Visualization and Reasoning battery of the Leiter-R can be combined into two separate
composites labeled Fundamental Visualization and Fluid Reasoning. In this study the latter composite was used, which comprises two subtests—Sequential Order and Repeated Patterns.
Sequential Order includes items such as a cat increasing in size
where the child has to identify the correct next-sized cat from
two possibilities. In the Repeated Patterns subtest the child has
to complete patterns such as red-yellow-blue-red-yellow-?-?.
Testing is stopped after seven errors for Sequential Reasoning
and six errors for Repeated Patterns. Here, each subtest score
is converted to a scaled score, which in turn are combined and
converted to a scaled score, where the norms based on hearing children have a mean of 100 and standard deviation of 15.
Children between 2 and 16 years of age can be administered this
test. In the statistical analyses the Fluid Reasoning composite is
referred to as the “visual sequential reasoning” variable.
Speech • Children’s Speech Intelligibility Measure (Wilcox &
Morris 1999). In this test 50 words are modeled verbally by the
examiner, and the child repeats each word, which is digitally
recorded. After administration of the test a judge listens to the
recording and identifies the word he or she believes the child
had said from a list of 12 phonetically similar possibilities. For
example, for the target word “learn” the 12 possible choices
are burn, churn, firm, first, germ, hurt, jerk, learn, purse, stern,
term, and turn. An intelligibility rating is calculated by multiplying by 2 the total number of words the judge correctly identifies, giving a possible range of 0 to 100. This test was developed
for children aged 3 years to 10 years 11 months, so some of
our sample participants were older than the upper limit. However, given that the test scores are not converted to age-based
standard scores, and that many of our participants might be
expected to have poorer speech intelligibility than their hearing
age-matched peers, it was considered acceptable to extend the
age range by 1 year. The Children’s Speech Intelligibility Measure has good test–retest reliability, and inter-rater reliability on
22 randomly selected participants was found to be 0.93.
Phonological Processing • Repetition of Nonwords Subtest:
NEPSY second edition (NEPSY II; Korkman et al. 2007).
This subtest is for children aged 5 to 12 years. The child listens to a series of increasingly complex nonwords (e.g., “crumsee” through “indobtreelob” to “splinkdellblee”). The child
5
repeats back each word, and scores one point for each correct
­syllable. Testing is stopped after four consecutive item scores
of zero. The total score is converted to a scaled score where
the mean is 10 and standard deviation is 3, based on hearing
children norms.
Phonological Processing Subtest: NEPSY II. This subtest
comprises two tasks that assess phonemic awareness. The first,
the word segment recognition requires identification of words
from word segments, for example, three pictures are named by
the examiner—“pencil,” “window,” and “ice cream,” then the
child is given the cue “indow” and asked to point to the correct
picture. The second, the phonological segmentation is a test of
elision where the child is asked to repeat a word and then create
a new word either by omitting a syllable or a phoneme, or by
substituting one phoneme in a word for another (e.g., “say ‘mistaken,’ now say it again but don’t say ‘mis’”). The child scores
one for each correct response and testing is stopped after six
consecutive incorrect responses. The test is for children aged 5
to 16 years and yields scaled scores where the mean is 10 and
standard deviation is 3.
Vocabulary Knowledge • Expressive Vocabulary: Test of
Word Knowledge (Wiig & Secord 1992). Children are shown
a series of pictures and asked to either name them (if a noun
such as a kangaroo) or tell the examiner what is happening (if
a verb such as melting). Many of the items have more than one
possible correct response. Each correct answer is given one
point, testing is stopped after five consecutive errors and the
total number of correct responses is converted to a scaled score
(mean 10, SD 3, based on norms for hearing children). The test
is for children aged between 5 and 17 years.
Receptive Vocabulary: Test of Word Knowledge. Here the
task is for the child to point to one picture from four possible
options, which best represents the word spoken by the examiner.
The words include nouns, verbs, and adjectives. Other details
are the same as for the expressive vocabulary test.
Reading • Word Reading Subtest: Wechsler Individual Achievement Test-II UK (WIAT-II UK). This test for children aged
between 4 to 16 years, starts with assessing the child’s knowledge
of letter names and sounds and progresses through to reading
individual words of increasing difficulty. Testing is stopped after
seven consecutive errors. The number of correct responses is converted to a standard score (again, mean 100, SD 15).
Procedure
Ethical approval for the study was received from the National
Research Ethics Service and the project complied with institution research regulatory board procedures.
Parents and children were provided with written information describing the study and any questions they had regarding it were addressed before obtaining written consent from the
parents. The children also gave verbal assent to participation,
having been assured that their participation was voluntary and
they could stop at any time should they wish. However, no child
asked to stop before completion of all the tests they were able to
undertake. Children implanted bilaterally were tested wearing
both implants, and those who usually wore a conventional hearing aid contralaterally to their implant were tested while using it
together with their cochlear implant.
The children were tested individually in a clinic room at
the hospital, at their school in a quiet room, or in their home,
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EDWARDS AND ANDERSON / EAR & HEARING, VOL. XX, NO. X, XXX–XXX
according to parental preference. Testing lasted a maximum of
90 min and the children were offered a break part of the way
through the session.
Tests were administered in the same order for each child,
according to the standard procedures provided in the test
manuals.
RESULTS
Descriptive statistics for each of the variables (visual memory, visual reasoning, auditory memory, speech intelligibility,
phonological processing, vocabulary, and reading) are presented in Table 2. These results indicate that our sample of children with cochlear implants are, on average, performing within
the normal range compared with hearing children on most, but
not all, of the tests. The notable exceptions, where the mean
score for the sample was around 1 SD or more below the norm
for hearing children, were auditory memory span, phonological
processing (NEPSY II), receptive and expressive vocabulary,
and word reading (WIAT-II). The percentage of children scoring 1 SD or more below the standardized mean ranged from 7
to 56% across the variables.
Table 3 gives the first order, Pearson correlations between
each of the variables. All the correlations were positive and statistically significant, the majority at the p < 0.001 level.
To further test the associations between the visual memory
span and visual sequential reasoning predictor variables and
the speech intelligibility, phonological processing, vocabulary
and reading composite outcome variables, a series of multiple
regression analyses was performed. Three variables required
logarithmic transformation to make the data normally distributed; these were receptive vocabulary, expressive vocabulary,
and speech intelligibility. Two sets of analyses were then conducted, the results of which are presented in Tables 4 and 5. In
both sets of analyses, in the first model only the child’s age at
implantation was entered as the independent variable. Age at
implantation was chosen because previous research has found
it to be the most robustly significant predictor of speech and
language outcomes after pediatric implantation. It accounted
for between 7 and 15% of the variance across the outcome variables. For each outcome variable, the younger the child was
when they received their implant, the better their performance.
In the first analysis, in the second model age at implantation
was entered as the first step and then auditory memory span was
added in the second step. This analysis showed that auditory
memory span is highly significantly associated with outcomes
after accounting for age at implantation. In the case of nonword
repetition, this model accounted for 73% of the variability in
scores.
In the second analysis, in the first model age at implantation was again entered as the first step. In the second step,
visual sequential reasoning and visual memory span were
added simultaneously. Table 5 indicates that for every outcome variable, visual sequential reasoning and visual memory
span together substantially increased the amount of variance
accounted for, after that attributed to the child’s age at implantation. Visual sequential reasoning and visual memory span
together accounted for between 16 and 25% of additional variance. In each case the increase was statistically significant at the
p = 0.01 level or less. Inspection of the β coefficients reveals
that for the phonological processing subtest of the NEPSY
II, visual sequential reasoning was the statistically significant
explanatory variable. For each of the other outcome variables,
visual memory span made the significant contribution to the
variance accounted for by the model.
DISCUSSION
Understanding and explaining the considerable variability between individuals in outcomes after pediatric cochlear
TABLE 3. Correlations between the visual memory, visual sequential reasoning, auditory memory, phonological processing, vocabulary
and reading variables
Visual
Sequential
Reasoning*
(Leiter-R)
Visual Memory Span
(Leiter-R)
Auditory Memory Span
(CMS)
Children’s Speech
Intelligibility Measure
Phonological Processing
(NEPSY II)
Repetition of Nonwords
(NEPSY II)
Receptive Vocabulary
(TOWK)
Expressive Vocabulary
(TOWK)
Word Reading
(WIAT-II)
Visual
Memory
Span
(Leiter-R)
Auditory
Memory
Span
(CMS)
Children’s
Speech
Intelligibility
Measure
Phonological
Processing
(NEPSY II)
Repetition of
Nonwords
(NEPSY II)
Receptive
Vocabulary
(TOWK)
Expressive
Vocabulary
(TOWK)
0.532
0.320
0.397
0.356
0.390
0.653
0.474
0.370
0.624
0.730
0.374
0.426
0.836
0.736
0.754
0.388
0.442
0.544
0.500
0.666
0.566
0.309
0.381
0.636
0.593
0.592
0.659
0.693
0.443
0.417
0.638
0.703
0.812
0.777
0.732
0.723
Figures in italics are significant at p = 0.05 (two-tailed).
Figures in bold are significant at p = 0.01 or less (two-tailed).
*Fluid Reasoning composite of the Leiter-R comprising the Sequential Order and Repeated Patterns subtests.
CMS, Children’s Memory Scale; TOWK, Test of Word Knowledge; WIAT–II, Wechsler Individual Achievement Test–II.
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
7
EDWARDS AND ANDERSON / EAR & HEARING, VOL. XX, NO. X, XXX–XXX
TABLE 4. Regression analyses of age at implant and auditory memory span on measures of speech, phonological
processing, vocabulary knowledge, and reading outcomes
Phonological
Processing
(NEPSY II)
n = 64
p
β coeff.
Model 1
Age at implant
R2
Model 2
Age at implant
Auditory Memory Span
R2
Nonword
Repetition
(NEPSY II)
n = 65
−1.093
β coeff.
0.463†
p
Expressive
Vocabulary
(TOWK)
n = 66
p
β coeff.
p
β coeff.
Children’s
Speech
Intelligibility
Measure
n = 65
Word
Reading
(WIAT-II)
n = 65
p
β coeff.
β coeff.
p
0.002
−0.941
0.010
0.101
−0.041
0.026
0.076
−0.046
0.011
0.097
−5.260
0.005
0.120
−0.072
0.109
0.040
0.005
0.000
−0.521
0.011
1.048
0.000
0.729†
−0.028
0.083
0.034
0.000
0.330†
−0.029
0.037
0.041
0.000
0.482†
−3.664
0.013
3.978
0.000
0.464†
−0.037
0.338
0.084
0.000
0.315†
0.148
−0.788
0.717
Receptive
Vocabulary
(TOWK)
n = 65
Significance of the change in R2 between model 1 and model 2:
*p < 0.01;
†p < 0.001.
TOWK, Test of Word Knowledge; WIAT–II, Wechsler Individual Achievement Test–II.
implantation is increasingly the focus of research in this field.
Deaf children who receive cochlear implants, even if early in
life, remain at risk of delays in developing language and literacy
skills, although many do achieve these at a level comparable
with that of their hearing peers. Previous research has sought
to identify cognitive or information-processing factors that are
associated with outcomes, but has typically focused on verbal
measures such as nonword repetition, auditory–verbal memory,
and verbal rehearsal speed (e.g., Dillon & Pisoni 2006; Pisoni
et al. 2010; Casserly & Pisoni 2013), rather than nonverbal
visual cognitive predictors. Unfortunately, many of the tests
that assess these abilities cannot be undertaken by young deaf
children, especially those children with specific language or
learning difficulties, as the tests rely on a basic level of spoken
language understanding and production for their administration.
Therefore, the primary aim of this study was to explore
whether certain visual cognitive processing abilities, which can
be assessed in very young deaf children before spoken language
skills emerge, are also associated with a range of speech, language, and literacy outcomes after cochlear implantation.
However, before testing the primary hypothesis, it is useful
to consider the context for our findings in terms of the actual
outcomes achieved in our sample, and whether the associations
between the speech, phonological processing, language and literacy outcomes are consistent with previous research on this
issue. In our group of children aged between 5 and 12 years,
who had been using a cochlear implant for between 1 and 10
years, around half of the children achieved below the normal
range for hearing children (i.e., 1 SD), in their auditory memory
span, and receptive and expressive vocabulary knowledge. One
third or more of the children scored below the normal range
on tests of word reading and phonological processing. Together
these results suggest that a substantial proportion of the children have auditory–verbal memory capacity deficits and are
experiencing difficulties developing the phonological processing skills that underpin the development of a wide vocabulary
TABLE 5. Regression analyses of age at implant, visual memory span and visual sequential reasoning on measures of
speech, phonological processing, vocabulary knowledge, and reading outcomes.
Phonological
Processing
(NEPSY II)
n = 64
β coeff.
p
Model 1
Age at Implant
−1.093
0.002
R2
0.148
Model 2
Age at Implant
−0.920
0.004
Visual Sequential
0.088
0.017
Reasoning†
Visual Memory Span† 0.254
0.109
R2
0.345†
Nonword
Repetition
(NEPSY II)
n = 64
β coeff.
−0.950
p
0.010
0.102
−0.848
0.044
0.013
0.260
0.454 0.010
0.293*
Receptive
Vocabulary
(TOWK)
n = 64
β coeff.
p
Expressive
Vocabulary
(TOWK)
n = 65
β coeff.
−0.043
0.083
0.021
−0.048
−0.038
0.002
0.021
0.320
−0.044
0.002
0.028 0.001
0.327†
p
0.008
0.107
0.010
0.407
0.022 0.014
0.266*
Children’s
Speech
Intelligibility
Measure
n = 64
Word
Reading
(WIAT-II)
n = 64
β coeff.
−5.460
p
0.003
0.130
−4.749
0.337
0.005
0.085
1.988 0.021
0.332†
β coeff.
p
−0.074
0.103
0.042
−0.075
−0.003
0.081
0.613
0.072 0.002
0.215*
†These variables were entered into the regression model simultaneously.
Significance of the change in R2 between model 1 and model 2:
*p < 0.01;
†p < 0.001.
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
8
EDWARDS AND ANDERSON / EAR & HEARING, VOL. XX, NO. X, XXX–XXX
and good reading skills. Few of the children demonstrated substantial difficulty with the visual sequential reasoning or visual
memory span tasks. It is not surprising that these children experienced much less difficulty with these tasks compared with the
language or literacy tasks, but more surprising that the percentage of children scoring more than 1 SD below the mean was less
than that based on normative data. The most likely explanation
for this is sampling bias, as the group was self-selected.
Consistent with previous research, we found auditory memory span (as a measure of auditory memory capacity) to be very
strongly related to all outcomes, from phonological processing
skills through to reading of single words. In particular, auditory
memory span was a highly significant predictor of nonword repetition ability, accounting for 62% of the variance after taking
account of the age at which the child was implanted. Poor performance on nonword repetition tasks is thought to reflect weak
or underspecified phonological representations of words in the
mental lexicon (Dillon & Pisoni 2006), which could occur as
the result of the degraded auditory representation of speech provided by a cochlear implant. Nonword repetition deficits have
been associated with poorer vocabulary knowledge and reading
skills, and our results are consistent with this.
The main purpose of this study was to explore the possibility that nonverbal visual cognitive processing factors may be
useful in accounting for the variability in phonological processes, language and literacy abilities in children with cochlear
implants. The measures of visual memory and reasoning ability
were chosen based on a combination of theoretical and clinical
rationale. In particular, the tests are clinically useful because
they can be administered to very young deaf children who have
not yet developed the spoken language skills needed to undertake the tests previously identified as associated with outcome
(e.g., digit span, nonword repetition, or phonological processing). The results of this study suggest that these visual, nonverbal tests may indeed provide useful information for identifying
children at risk of poor progress after cochlear implantation.
The combination of visual memory span and visual sequential
reasoning measures increased the amount of variation explained
in the speech and language outcomes by around 20%, over
that accounted for by age at implantation. For the majority of
the outcome measures, visual memory span made the significant contribution to the variance accounted for by the regression models. It is interesting to note that the exception was the
Phonological Processing subtest from the NESPY II where
the visual sequential reasoning variable (the Fluid Reasoning
composite from the Leiter-R) accounted for the significant proportion of variance. The NEPSY II Phonological Processing
subtest may be considered to place greater processing demands
on sequential processing skills, as the more difficult items in
this test require the child to manipulate phonemes within words
and produce them in the correct order.
The relationship between visual memory span and outcomes
is particularly interesting given that overall, as a group, these
children with cochlear implants were performing well within the
normal average range on the test of visual memory span, (only
7% of the sample scored 1 SD or more below the mean for the
normalization sample). This suggests that clinically, if a child
achieves a poor score on this test, further investigation of their
information-processing abilities should be undertaken to assess
specific areas of difficulty. In a clinical setting therefore, before
the child has well-established spoken language capabilities,
assessing his or her visual memory span and visual sequential
reasoning abilities may provide useful information in deciding
whether he or she is at risk of making poor progress in developing phonological processing skills, language and later on literacy
skills. Similarly, when presented with a child who is making
unexpectedly poor progress after implantation, and who may
as yet be unable to tackle the more traditional, ­language-based
assessments of specific learning difficulties, assessing these
visual information-processing skills may be informative. If the
child has some ability to produce spoken words, specifically
the numbers one to nine, the results of this study suggest that
administering a standardized test of auditory digit span such as
that from the Children’s Memory Scale or Wechsler Intelligence
Scale for Children IV, will provide further useful information.
Clearly there are a number of other potential factors that contribute to the variance in outcomes, which would also need to be
explored in a clinical assessment, such as the presence of a family history of dyslexia or specific language disorder, the degree of
parental involvement in the child’s rehabilitation, any brain abnormalities evidenced on magnetic resonance imaging scans (for
example after meningitis), or the child’s exposure to more than
one spoken language in the home. All of these are likely to have
an impact on progress in developing speech, language and literacy
skills, but could not be quantified or accounted for in this study.
Theoretically, as Pisoni et al. (2008, p. 61) note, the absence
of auditory stimulation may disturb the development of neural
systems and circuits other than those primarily involved in auditory processing (i.e., motor and visual systems), before implantation takes place. Delays in language acquisition during early
development is likely to produce effects on processes not necessarily related to the early sensory processes of audition, for example, executive functions such as problem solving, attention and
memory, particularly, memory for sequences and temporal order
information. Therefore, in terms of our findings it is plausible that
nonverbal, visual cognitive processes such as visual sequential
memory, and visual sequential reasoning are affected by the early
distortion or absence of auditory stimulation of the brain.
As with much research in this area, one limitation of this
study is the sample size, which while respectable in comparison
with other published studies on pediatric cochlear implantation
of this nature, is modest in view of the statistical analyses used.
A second possible limitation is the range of measures used as
either explanatory and outcome variables. In particular there are
a relatively limited number of standardized visual tests available
assessing reasoning or memory abilities, and even fewer that can
be administered to young children. In contrast there are many
potential tests of language and literacy and it was necessary to
choose a selection that would hopefully cover a range of speech,
phonological processing, language and literacy outcomes.
In this study we examined the association between nonverbal cognitive abilities and outcomes in children aged between
5 and 12 years, some of whom had been using their cochlear
implant for more than 8 years. Therefore for these children,
valuable time has elapsed when specific information-processing
deficits may have been identified and remedial intervention provided, for them to maximize the benefit to be derived from the
implant(s). The advantage of the tests of visual sequential reasoning and memory used in this study is that they can be administered to deaf children as young as 2 years of age. For some
children, this could be before they have actually received their
cochlear implant(s). Therefore, for the first time, we have been
Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
EDWARDS AND ANDERSON / EAR & HEARING, VOL. XX, NO. X, XXX–XXX
able to identify potential early information-processing indicators of children at risk of difficulties in developing speech, language and literacy skills after cochlear implantation. However,
it is recognized that observing an association between nonverbal cognitive abilities and outcomes at one time point postimplantation does not necessarily mean that these same cognitive
abilities, if measured in younger deaf children, are predictive of
future difficulties: this needs to be the focus of further research.
ACKNOWLEDGMENTS
The authors declare no conflict of interest.
Address for correspondence: Lindsey Edwards, Great Ormond Street
Hospital for Children, Cochlear Implant Programme, Great Ormond
Street, London WC1N 3JH, England, United Kingdom. E-mail: Lindsey.
[email protected]
Received 13 September, 2012; accepted 13 October, 2013.
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