Cameron et al – SPD Indigenous Children
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Prevalence and Remediation of Spatial Processing Disorder (SPD) in Indigenous Children in
Regional Australia
Sharon Cameron a
Harvey Dillon a
Helen Glyde a
Sujita Kanthan a
Anna Kania a
a
National Acoustic Laboratories
KEY WORDS: spatial processing disorder; chronic otitis media; deficit-specific auditory
training.
Abbreviations:
4FAHL
ACMS
AEO
CANS
CAPD
COM
GLM
HRTF
Leq
LIFE
LiSN-S
NAL-RP
PGA
SNR
SPD
SRT
Four-frequency average hearing level
Aboriginal Corporation Medical Service
Aboriginal Education Officer
Central auditory nervous system
Central auditory processing disorder
Chronic otitis media
General linear model
Head-related transfer function
Equivalent continuous sound pressure level
Listening Inventory for Education
Listening in Spatialized Noise – Sentences Test
National Acoustic Laboratories – Revised Profound
Prescribed gain amplifier
Signal-to-noise ratio
Spatial processing disorder
Speech reception threshold
Corresponding Author:
Sharon Cameron, PhD
Senior Research Scientist
National Acoustic Laboratories
Australian Hearing Hub
16 University Avenue
Macquarie University NSW 2109
Australia
Phone: +61 2 9412 6851
Fax:
+61 2 9412 6769
e-mail: Sharon.Cameron@nal.gov.au
Cameron et al – SPD Indigenous Children
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Objective: This study aimed to determine the prevalence of spatial processing disorder
(SPD) in the Indigenous Australian population and the benefit of and logistical issues arising
from remediation of the disorder.
Design: Participants were assessed for SPD with the Listening in Spatialized Noise –
Sentences test (LiSN-S). Participants diagnosed with SPD were instructed to use the LiSN &
Learn auditory training software until 100 games had been completed.
Study Sample: Participants were 144 Indigenous Australian children (aged between 6;0
[years;months] and 12;2).
Results: Ten participants (6.9 per cent) presented with SPD. Nine took part in the auditory
training study. Post-training LiSN-S performance improved on average by 0.9 population
standard deviations (1.4 dB). There was a significant correlation (r = 0.71, p = 0.031, η2 =
0.51) between total number of LiSN & Learn games played (mean = 65, SD = 27) and
improvement in LiSN-S performance. Teachers rated all participants as improving in their
listening abilities post-intervention.
Conclusions: There is a high prevalence of SPD in the Indigenous Australian population.
LiSN & Learn training is effective in remediating SPD in this population and is considered a
beneficial intervention by teachers, however improvement in spatial processing is dependent
on training program uptake.
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Spatial processing disorder (SPD) is a specific form of central auditory processing disorder
(CAPD) which is characterized by a deficit in the ability to utilize binaural cues to achieve
spatial release from masking. The functional manifestation of SPD is an inability to
understand speech when background noise is present. SPD can occur in children and adults
with normal hearing thresholds (Cameron & Dillon 2008, 2011, in press; Cameron et al,
2012) as well as children and adults with mild to moderately-severe hearing impairment
(Glyde et al, 2011, 2013) and other clinical groups (Rance et al, 2012 a & b). For those with
normal hearing thresholds, SPD is thought to result from an inability to differentiate the
differences in the time and intensity of auditory signals arriving at the two ears from various
locations in the environment (Cameron et al., 2012). As a result, children diagnosed with
SPD need a significantly greater signal-to-noise ratio (SNR) in the classroom in order to
achieve the same speech reception thresholds (SRTs) as normally-hearing children without
the disorder.
SPD can be diagnosed with the Listening in Spatialized Noise – Sentence test (LiSN-S,
Cameron & Dillon, 2009). The LiSN-S is an adaptive, virtual-reality test that measures the
ability of people to use the spatial cues that normally help differentiate a target talker from
distracting speech sounds (Figure 1). The LiSN-S target sentences and distracter speech
materials have been synthesized with head-related transfer functions (HRTFs) to create a
virtual auditory reality effect (Cameron et al, 2009, Cameron & Dillon, 2007). A diagnosis of
SPD is characterized by a pattern of depressed scores on the spatially separated conditions of
the LiSN-S compared to the co-located conditions (Cameron & Dillon, 2011). One-sided
critical difference scores (required to determine whether an individual has improved on the
LiSN-S following remediation) are available for children and adults aged 6 to 60 years
Cameron et al – SPD Indigenous Children
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(Brown et al. 2010; Cameron et al, 2011). In order for the LiSN-S to be used with the
hearing-impaired population the software was modified to incorporate a prescribed gain
amplifier (LiSN-S PGA) that amplifies and shapes the target and distracting stimuli
according to the National Acoustic Laboratories – Revised Profound (NAL-RP) prescription
(Glyde et al, 2013).
SPD has been shown to be reversible in normal-hearing children with deficit-specific
auditory training software (Cameron & Dillon, 2012). The LiSN & Learn software, which
was developed specifically to remediate SPD, produces a virtual reality auditory environment
under headphones and is designed to be used in the home. Full details of the LiSN & Learn
development can be found in Cameron & Dillon, 2011. In summary, the child’s task is to
identify a word or words from a target sentence by selecting a matching image on the
computer screen. The target sentences are presented in spatially separated background noise.
The test configuration is the same as the LiSN-S Same Voice ±90° condition (see “same
voice/different directions” box in Figure 1). This configuration maximizes reliance on use of
spatial processing cues to differentiate the target from the distracters. A weighted up-down
adaptive procedure is used to adjust the signal level of the target based on the child’s
response. The child plays two games per day, five days a week (taking approximately 15
minutes per day) until at least 100 games have been completed. In a preliminary study
(Cameron & Dillon, 2011), nine children who were diagnosed with the LiSN-S as having
SPD trained with the LiSN & Learn software. All the children were within normal limits on
the LiSN-S post training, improving significantly on the conditions of the LiSN-S which
measure spatial processing (p ranging from < 0.003 to 0.0001). Further, in a randomized,
blinded, controlled study, Cameron et al (2012) found that the improvement in spatial
processing following training was specific to the LiSN & Learn software. In both studies, the
Cameron et al – SPD Indigenous Children
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participants’ SRTs on the LiSN & Learn improved by approximately 10 dB over the course
of the training. Improvements on behavioural tests were in line with self-report, parent and
teacher ratings of listening ability post training. For a comprehensive review see Cameron
and Dillon (in press).
The prevalence of CAPD is said to be 2 – 3% (Chermak & Musiek, 1997). However, the
exact proportion of individuals with SPD in the general population is unknown. In an
evaluation report on a trial to assess and remediate CAPD conducted by Australian Hearing
between April 2012 and February 2013, it was reported that 19 per cent of children (69 of
359) referred for assessment due to reported listening difficulties, presented with SPD as
diagnosed with the LiSN-S (unpublished report by Australian Hearing). Further, Dillon et al
(2012) reported that 17.5 per cent of children (32 of 183) referred for assessment for CAPD
in various studies at the National Acoustic Laboratories have been diagnosed with SPD.
Approximately 50 per cent of the children in these studies presented with a history of chronic
otitis media (COM). Kapadia et al. (2012) found significantly poorer spatial processing
ability (p = 0.012), as measured by the LiSN-S, in a group of 17 six year old children with a
history otitis media with effusion requiring ventilation tubes.
It may be hypothesized that fluctuating access to normal binaural cues during bouts of COM
may negatively influence the development of spatial processing mechanisms within the
central auditory nervous system (CANS). To this end, the conductive hearing loss caused by
otitis media decreases the inter-aural cues present in the two cochlea, so the CANS is unable
to develop the processing mechanisms that enable these cues to be used in understanding
speech in noisy places (Cameron & Dillon, in press). That is, the deprivation may lead to a
reduction in the number of synapses available to assist in binaural interaction. It is possible
Cameron et al – SPD Indigenous Children
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that for a proportion of these children, the processing mechanisms do not develop normally
even after hearing sensitivity returns to normal.
Indigenous Australian children have higher rates of middle ear disease than have been
described in any other population in the world. Estimates suggest that Aboriginal children in
Australia experience, on average, 2.6 years of conductive hearing loss. The equivalent figure
for non-Aboriginal children is three months (OATSIH, 2001). Studies conducted over the
years in regional areas of Australia have reported prevalence rates of middle ear
abnormalities in Indigenous children to be between 45-62% (Adams et al, 2004; Thorne,
2003). Given the high prevalence of middle ear disease in Indigenous communities, and the
aforementioned link between an early history of COM and SPD, it is expected that the
prevalence of SPD will be higher in the Indigenous population compared to the nonIndigenous population. The presence of SPD would contribute to listening difficulties in the
classroom and may limit the educational progress of Aboriginal children with the disorder.
Many of these children would have additional disadvantages arising from listening in their
second language (Nicholls, 2005), poor acoustics in the classroom (Massie et al., 2004), and
comorbid conductive hearing loss arising from current or past middle ear disorders (Thorne,
2003). Despite the negative impact that SPD could have on educational outcomes for
Indigenous Australian children there is currently no funding to cover services for children
with CAPD.
The focus of this research was to examine the prevalence of SPD in a sample Indigenous
Australian population. The pilot study additionally aimed to determine the benefit of
auditory training in the school setting in Indigenous Australian children diagnosed with SPD
Cameron et al – SPD Indigenous Children
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and to identify any logistical issues that would need to be resolved if a national program to
diagnose and remediate this disorder were to be mounted.
Methods
Approval for the study discussed in this paper was granted from the Australian Hearing
Human Research Ethics Committee, as well as the Student Engagement and Program
Evaluation Bureau of the NSW Department of Education and Communities. Additional
approvals were obtained from the NSW Aboriginal Education Consultative Group (Lower
North Coast Region) and the Durri Aboriginal Corporate Medical Service.
Participants
Data was collected from a total of 144 children aged between 6;0 [years;months] and 12;2
(mean age 8;10). There were 69 males and 75 females. Participants were recruited from four
government primary schools in Kempsey, NSW, being Kempsey East public school,
Kempsey West public school, Kempsey South public school and Green Hill public school. In
addition to the 144 children who took part in the study, a total of 13 children met the study
exclusion criteria, as follows:
1. Children with a diagnosed intellectual disability or with documented unmedicated
attention deficit or hyperactivity disorder (ADHD) were excluded from the study due to
the impact of such conditions on the validity of diagnostic test results as well as on a
child’s ability to undertake daily auditory training. Six children were excluded based on
these criteria.
2. On the day of testing the children underwent a formal hearing assessment, including
direct diagnostic otoscopy, tympanometry and pure tone audiometry. If otoscopic
Cameron et al – SPD Indigenous Children
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examination revealed ear discharge the child was excluded from the study and referred
for appropriate medical advice. Two children failed the otoscopic examination.
3. Where hearing thresholds exceeded normal limits (>20 dB at 500 Hz, 1, 2 or 4 kHz),
unmasked and masked bone conduction was undertaken to determine the nature of the
hearing loss. Four children with a sensorineural hearing loss were excluded from the
study.
4. Children with a conductive loss were excluded if they had a four-frequency average
hearing level (4FAHL) ≥ 40 dB and/or the 4FAHL between the two ears by more than 20
dB to ensure adequate amplification during testing and LiSN & Learn training. One child
with a 4FAHL which differed between the ears by more than 20 dB was excluded.
Procedures: Pre- and Post-Training
The audiological measurements and the LiSN-S test were administered by three members of
the research team. Testing took approximately 30 minutes per child. Testing was carried out
in a quiet room, such as the school library, in the participating schools between 9 am and 3
pm. The LiSN-S is designed to be delivered in a sound-attenuated environment, such as an
audiological test booth. As such, maximum permissible noise levels for this test were
determined at each frequency (500 Hz, 1, 2, 4, 8 kHz). To ensure that these levels were not
exceeded the equivalent continuous sound pressure level (Leq) in dB at each school was
measured using a Brüel & Kjær type 2231 sound level meter. Measurements were taken
prior to each LiSN-S test session and if intermittent fluctuations in noise levels occurred,
such as if heavy vehicles passed outside. In such cases testing was suspended until acceptable
noise levels were recorded. The procedure used, prior to testing, to calculate the LiSN-S
permissible noise levels is detailed in Appendix A.
Cameron et al – SPD Indigenous Children
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Children who were diagnosed as having SPD were re-tested on the audiological measures and
LiSN-S post-training. Test-retest reliability on the LiSN-S measures ranged from r = 0.2 for
the spatial advantage measure to r = 0.7 for high cue SRT measure, with mean test-retest
differences ranging from a maximum of 0.7 dB on the high cue SRT to only 0.1 dB on the
total advantage measure (Cameron et al, 2011). Following training, teachers of the children
with SPD were requested to complete the Listening Inventory for Education (LIFE) –
‘Teacher Appraisal of Listening Difficulty’ questionnaire (Anderson & Smaldino, 1998) and
to forward these to the research audiologist.
AUDIOLOGICAL TESTING
Following otoscopic examination, audiometric and tympanometry evaluation was undertaken
using an Interacoustics® AA222 Audiotraveller diagnostic audiometer/impedance meter.
The transducers used for pure tone audiometry were E-A-RTone® 3A insert earphones
(unless contraindicated) in combination with MSA Left/Right™ 766243 headband earmuffs,
size “high” (yellow cup) in order to provide greater attenuation of ambient noise. Peltor H7A
supra-aural earphones were used for participants with contraindications, such as large
tympanic membrane perforations or ventilation tubes. Audiometry was conducted using 20
dB HL screening levels at 500 to 4000 Hz. For participants who did not pass the screening
cut-off, both air and bone conduction thresholds were obtained.
LiSN-S
The LiSN-S was administered using a personal computer and Sennheiser HD215 circumaural
headphones. The headphones were connected to the headphone socket of the PC via a Buddy
6G USB soundcard. The sensitivity of the soundcard was automatically set to a predetermined level by the LiSN-S software in order to achieve pre-designated signal levels,
Cameron et al – SPD Indigenous Children
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alleviating the need for daily calibration (Cameron et al, 2009). At this pre-set level, the
combined distracters at 0° had a long-term root mean square (RMS) level of 55 dB SPL as
measured in a Brüel and Kjær type 4153 artificial ear attached to a Brüel and Kjær sound
level meter, model 2231. The LiSN-S software creates a virtual reality auditory environment
under headphones by pre-synthesizing the speech stimuli with HRTFs. Target sentences are
perceived as coming from directly in front of the listener (0° azimuth). The distracter speech,
in the form of looped children’s stories, varies according to either their perceived spatial
location (0° vs + and -90° azimuth), the vocal identity of the speaker/s of the stories (same as,
or different from, the speaker of the target sentences), or both these parameters. The target
sentences are initially presented at a level of 62 dB SPL. The distracter stories are presented
at a constant level of 55 dB SPL (for the combined level of the two competing talkers). The
target and competing signals are presented to both ears simultaneously.
The listener’s task was to repeat back to the examiner the words heard in each target
sentence. If the participant made a grammatical mistake that was considered to be a cultural
norm (such as sawed for seen) the word was scored as correct. Up to 30 sentences were
presented in each of the four conditions of distracter location and voice: same voice at 0º,
same voice at ±90º, different voices at 0º and different voices at ±90º. The SNR was adjusted
adaptively in each condition by varying the target level. The adaptive procedure is performed
automatically by the software when the examiner enters the number of words in each
sentence that is correctly identified by the participant. The SNR was decreased by 2 dB if a
listener scored more than 50 per cent of words in a sentence correct, and increased by 2 dB if
he or she scored less than 50 per cent of words correct. The SNR was not adjusted if a
response of exactly 50 per cent correct was recorded (for example, 3 out of 6 words correctly
identified). A minimum of five sentences were provided as practice, however, practice
Cameron et al – SPD Indigenous Children
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continued until one upward reversal in performance (i.e., the sentence score dropped below
50 per cent of words correct) was recorded.
Testing ceased in a particular condition when the listener had either (i) completed the entire
30 sentences in any one condition; or (ii) completed the practice sentences plus a minimum of
a further 17 scored sentences, and their standard error, calculated automatically in real time
over the scored sentences, was less than 1 dB. A participant’s speech reception threshold was
calculated in each condition as the average SNR recorded for the scored sentences. The
procedure takes approximately 15-20 min to complete. As shown in Figure 1, performance on
the LiSN-S is evaluated on the same voice 0° condition (low cue SRT); the different voices
±90° condition (high cue SRT), as well as on three difference scores - talker, spatial and total
advantage. These advantage measures represent the benefit in decibels (dB) gained when
talker (pitch), spatial, or both talker and spatial cues are incorporated in the maskers,
compared to the baseline (low cue SRT) condition where no talker or spatial cues are present
in the maskers.
As previously mentioned, SPD is characterized by a pattern of depressed scores on the
spatially separated conditions of the LiSN-S compared to the co-located conditions. In this
study a participant was diagnosed as having SPD if his or her LiSN-S pattern score was more
than 1.96 population standard deviations below the mean. An individual’s pattern score,
which is calculated automatically by the LiSN-S software, is a measure of the benefit, in
decibels, of adding spatial information, averaged across the conditions where no talker cues
are available and the condition where there are talker cues available. The formula used to
derive the pattern measure is described in Cameron and Dillon (2011).
Cameron et al – SPD Indigenous Children
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LiSN-S PGA
Children with mild conductive losses as described in the Participants section were assessed
with the LiSN-S in prescribed gain amplifier mode. The participant’s right and left ear air and
bone conduction thresholds were entered and, as discussed in the introduction, the software
amplified and shaped the LiSN-S stimuli according to the child’s NAL-RP prescription
(Glyde et al, 2013).
LIFE QUESTIONNAIRE
The Listening Inventory for Education - Teacher Appraisal of Listening Difficulty (LIFE) is a
measure of improvement in listening ability following intervention. The LIFE has been a
widely used efficacy tool for more than ten years (Anderson, Smaldino, & Spangler, 2011).
The questionnaire is comprised of 16 items, each describing an educational situation. For
example, item 4 asks: Attention has improved when listening to directions presented to whole
class. Item 16 originally read: Based on my knowledge and observations I believe that the
amplification system is beneficial to the student’s overall attention. The words amplification
system were changed to auditory training software for the present study. A five-point
response scale is used from +2 (Agree) to -2 (Disagree). All items are added together to
produce a composite score on an incremental scale from -35 to +35. A score of 35 represents
strong positive change indicating that the intervention was highly beneficial. A score of 0
represents no change, and -35 suggests the intervention was highly unfavourable.
Procedures: Training
LiSN & LEARN
Children who were diagnosed as having SPD undertook auditory training with the LiSN &
Learn. Training took place in a quiet room in the school, such as the library, using a school
Cameron et al – SPD Indigenous Children
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computer and was carried out under the supervision of the participant’s school teacher or
Aboriginal Education Officer (AEO). The software was installed by the research audiologist,
who demonstrated the training program to the participant and his or her supervisor. All the
semantic items used in the development of the LiSN & Learn target sentences are acquired by
children aged 30 months of age (Cameron & Dillon, 2011). However, as English may not be
the first language of the Indigenous Australian children a word and picture flash cards were
used to familiarize the children with the LiSN & Learn target words to ensure that language
factors did not inhibit program usability (National Acoustic Laboratories, 2013). The LiSN
& Learn stimuli (target words and distracter stories) are presented through Sennheiser HD215
headphones. Calibration is undertaken at start up using a reference signal (whooshing sound;
speech-shaped random noise) that is adjusted by the child using a slider bar. The child is
instructed to move the slider bar until he or she can barely hear the whooshing sound. The
reference signal is level normalized so that its rms level is 40 dB less than the rms level of the
combined distracters stories. Thus, when presented, the sensation level of the combined
distracters is at least 40 dB SL. A starting level of 7 dB SNR is utilized. The children were
instructed to play two games per day, five days per week for 50 training sessions (i.e. until
100 games have been played). Training took approximately 15 minutes per day.
Five training games were used - Listening House, Listening Ladder, Answer Alley, Goal
Game and Space Maze. The first four games differ only in respect to the animations (e.g., the
game is set in a bowling alley in Answer Alley and a soccer field for Goal Game) and the
auditory stimuli used to provide feedback and positive reinforcement. The target and
distracter stimuli and the response protocol are identical for all games. In all games the
child’s task was to identify a word from a target sentence presented in background noise
consisting of two looped distracter stories. The target sentences emanated from 0° azimuth
Cameron et al – SPD Indigenous Children
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and the distracter stories emanated from + and - 90º azimuth. All speech stimuli are produced
by the same female speaker so the listener must predominantly rely on processing of spatial
cues to separate the target sentence from the distracter speech. A tone burst is presented
before each sentence to alert the child that a sentence will be presented. Immediately
following the presentation of the sentence four images and a question mark appear at the top
of the screen (Figure 2). In a five-alternative, forced-choice, adaptive method, the child uses
the computer mouse to select one of the images that matches a word from the sentence he or
she had just heard (or make an unsure response by selecting an image of a question mark). A
weighted up-down adaptive procedure is used to adjust the signal level of the target based on
the participant’s response. The target is decreased by 1.5 dB when the child correctly
identifies a target image. It is increased by 2.5 dB if the wrong target is identified, and it is
increased by 1.5 dB if an unsure (question mark) response is made. If the child selects the
unsure response for a particular sentence, that sentence is repeated at the higher SNR.
However if the child selects the unsure response again for that same sentence, a different
sentence is presented at a higher SNR. If the child selects a correct image, a short
congratulatory sound is presented (such as a bell). If the child selects an incorrect or unsure
image a short negative sound is presented (such as a buzzer). Different sounds and
animations are used as feedback for each of the four games. In the Space Maze game the
child hears an instruction (e.g., move up three spaces) and must use the computer mouse to
select a direction (up, down, left, right) and a number (from one to ten) in order to move
around the maze. The direction and number buttons remain on the screen throughout the
game.
A minimum of five sentences is provided as practice; however practice continues until one
upward reversal in performance (that is, the first incorrect or unsure response that occurs after
Cameron et al – SPD Indigenous Children
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a correct response) has been recorded. The SNR decreases in 3 dB steps during the practice
period. There are 40 sentences in any game. The child’s SRT for each game is measured as
the average SNR over all sentences, excluding the practice.
Feedback regarding the child’s performance during the game, positive reinforcement for
correct responses and progress indicators are incorporated into the software. Further, a
personalized avatar or “buddy” that the child designs on install provides positive feedback
throughout the training sessions. Players earn “currency” for completing games which can be
used to purchase items for their buddy in the LiSN & Learn reward shop or to play nontraining games that are incorporated in the software. In addition to the intrinsic rewards built
into the LiSN & Learn software, over the course of the training participants were offered
small, culturally-appropriate rewards (including stationery such as pencils and stickers for
reaching training milestones, and laminated certificates) as an incentive to continue with and
to complete training.
Results were recorded automatically by the software. Progress reports in the form of an Excel
spread sheet were generated by selecting the report generation button in the progress report
area. The participants’ teacher or the AEO were required to email these reports to the research
audiologist on a weekly basis. The research audiologist checked the reports each week to
ensure that the child was using the software as required by the study protocols. The four
participating schools were allocated a five-month period in which to complete the ten-week
training program, ranging from the start of the second NSW public school term on 23 April
2012 to the end of the third school term on 21 September 2012.
Results
Cameron et al – SPD Indigenous Children
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Analyses were performed with Statistica 10.1.
Prevalence of SPD
Fifteen of the 144 participants, or 10.4 per cent of the study sample, presented with a mild
conductive hearing loss (>20 dB at 500 Hz, 1, 2 or 4 kHz and 4FAHL < 40 dB). Performance
on the LiSN-S - as determined by each participant’s pattern measure expressed as a Z-score was normally distributed as determined by the Shapiro-Wilk test of normality (p = 0.232).
However, as shown in Figure 3, performance was negatively skewed, presumably due to the
high incidence of COM in the Indigenous Australian population.
Ten participants, or 6.9 per cent of the study sample, presented with a spatial processing
disorder (SPD) as determined by his or her LiSN-S pattern score. Of the ten children with
SPD, four had a mild conductive hearing loss. Nine of the ten children with SPD (four males
and five females) went on to train with the LiSN & Learn. The other child withdrew from the
study as he was not willing to undertake the training. Details of the hearing thresholds and
middle ear function pre- and post-training of the nine children who undertook the LiSN &
Learn remediation are presented in Table 1.
Results of LiSN & Learn Training
Figure 4 shows the individual participant improvement in SRT in dB on the LiSN & Learn
over time (expressed as a five-day running average) for the nine children who took part in the
training study. None of the children completed the entire training program of 100 games. On
average the participants played 65 games (SD 27) with a range of 25 to 98 games. It can be
seen in Figure 4 that some participants showed a dip in performance during training. The
student learning support officer supervising the training of participants 518, 523 and 524
Cameron et al – SPD Indigenous Children
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advised that ear infections were suspected during this period. Upon further inspection it was
noted that the children were not undertaking the calibration procedure (i.e. they were moving
the slider bar to the same spot without listening to the calibration tone). The supervisor
instructed these participants to “blow their noses” before each test to attempt to equalize the
pressure in their middle ear cavities and also assisted in the calibration process. This resulted
in the return to more linear improvement in SRT on the LiSN & Learn as shown in the graph.
The pre- and post-training LiSN-S pattern Z-scores for each participant - together with
number of games played and LIFE teacher ratings - are documented in Table 2. The mean
pre-training LiSN-S pattern Z-score was -2.6 population SD units from the mean (SD = 0.4).
There was a trend of improvement on the LiSN-S post training, with the mean LiSN-S Zscore improving to -1.7 (SD = 2.4), as shown in Figure 5. Repeated measures Analysis of
Variance (ANOVA) with number of games played as a continuous predictor showed that
there was no significant difference between pre- and post-training performance (F (1, 7) =
3.80, p = 0.092, η2 = 0.35). There was, however, a significant interaction between degree of
improvement and number of LiSN & Learn games completed (F (1, 7) = 7.19, p = 0.031, η2 =
0.51). The correlation between performance improvement and games played was r = 0.71.
Thus children who played more games on the LiSN & Learn improved more on the LiSN-S,
as shown in Figure 6.
Group performance on the various LiSN-S SRT and advantage measures pre- and posttraining is illustrated in Figure 7. Mean scores were calculated from the individual standard
scores (or Z-scores) for each of the nine participants in the LiSN & Learn study. Performance
improved post-training in every LiSN-S condition except for talker advantage, however, as
evidenced by the error bars representing the 95 per cent confidence intervals, there was more
Cameron et al – SPD Indigenous Children
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variation post-training. This degree of variation is consistent with the interaction of amount of
training on LiSN-S performance described above. Thus whereas repeated measures ANOVA
showed that the effect of training was significant when averaged across all measures (F (1, 8)
= 10.34, p = 0.012, η2 = 0.56), Tukey HSD post-hoc multiple comparison test revealed that
post-training improvement of 1.2 population SDs (4.0 dB) was significant only for the high
cue SRT condition (p = 0.027). High cue SRT is the LiSN-S condition that is most similar to
real-life listening in that the distracters are spatially separated and distracter voices are
different to that of the target speaker. The degree of improvement in the high cue SRT
condition is partly due to an improvement in some ability in the participants (such as auditory
vigilance) that applies even when there is no spatial separation, as evidenced by the
improvement in the low cue condition of 1.9 population SDs (2.8 dB), as well as
improvement in spatial processing ability.
Post-Training Teacher Ratings of Listening Ability
The individual participant LIFE –Teacher Appraisal of Listening Difficulty questionnaire
results are provided in Table 2. As described in the methods section, the LIFE is a measure of
real-world improvement in listening ability following some form of intervention, in this case
LiSN & Learn auditory training for SPD, on a scale of -35 to +35. The mean rating was +24
(SD 10). However there was no significant correlation (r = -0.10) between the teacher ratings
and the participants’ post-training improvement in LiSN-S pattern Z-score (F (1, 7) = 0.07, p
= 0.797, η2 = 0.06) or improvement in high cue SRT Z-scores (F (1, 7) = 0.03, p = 0.867, η2 =
0.00).
In order to investigate the study aims of determining the benefit of auditory training in the
Indigenous Australian population and identify any logistic issues that may impact a national
Cameron et al – SPD Indigenous Children
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program to identify and remediate SPD, school principals, class teachers and the
teachers/support staff who supervised the LiSN & Learn training were asked to provide
qualitative feedback on the progress of the LiSN & Learn training. These details are
provided in Appendix B. The qualitative feedback was obtained during and after training, and
before reassessment on the LiSN-S. To protect participant confidentiality, ID numbers have
been removed from these comments and number of games played is noted as a range (< 50 or
> 50). Post-training performance on the LiSN-S is noted as “pass” or “fail” based on the
LiSN-S pattern score.
Discussion
The initial aim of this study was to investigate the prevalence of SPD in the Indigenous
Australian population. As reported in Dillon et al (2012) children with SPD commonly
present with a history of chronic otitis media, and the incidence of COM is particularly high
in the Indigenous Australian population. The prevalence of SPD in the study sample of 144
children drawn randomly from the Indigenous population in a regional town was indeed high
at 6.9 per cent.
The second objective of the study was to determine whether the benefits of auditory training
with the LiSN & Learn software for non-indigenous children with SPD reported by Cameron
& Dillon (2011) and Cameron et al (2012) would be found in the Indigenous Australian
population in this study. In the present study, improvement in spatial processing post training
was measured by LiSN-S performance as well as teacher ratings of improvement in listening
ability following intervention using the LIFE questionnaire. On average, post-training LiSNS performance improved by nearly one population standard deviation. However, LiSN-S
performance was variable and significantly related to the number of LiSN & Learn training
Cameron et al – SPD Indigenous Children
20
games played by the participant (r = 0.71, p = 0.031, η2 = 0.51). Whereas all participants
were requested to complete 100 games over 50 training sessions, actual uptake ranged from
25- 98 games (mean 65 games). This was despite providing children in this study with
rewards - additional to those intrinsic in the software – such as culturally-appropriate
stationery and laminated certificates.
All teachers rated the LiSN & Learn intervention as beneficial for their respective students.
On a scale of -35 to +35, the mean LIFE rating was +24 (range +11 to +35). Interestingly,
however there was no significant correlation between the teacher ratings and the participants’
post-training improvement in LiSN-S pattern Z-score (r = -0.10, p = 0.797, η2 = 0.06). An
inspection of the qualitative feedback from teachers provided in Appendix B showed that
even for children who completed less than half the required number of training games and
whose LiSN-S performance was not within normal limits post-training, teachers felt that the
training was beneficial to the child’s listening performance in the classroom. Feedback
indicated that the confidence of these children had improved, as had their classroom
participation. It could be hypothesized that in the early stages of training the child may learn
aspects of auditory vigilance that may assist in classroom situations. This hypothesis is
supported by the attentional improvements measured post LiSN & Learn training in Cameron
and Dillon (2011). However, the study has confirmed that spatial processing ability improves
proportionately to the number of LiSN & Learn training games completed. To this end it may
be speculated that regardless of whether a child’s confidence improves as a result of
undertaking training, sustained listening performance would still be impacted due to aspects
of auditory fatigue that would occur if the underlying binaural processing deficit remained
unremediated.
Cameron et al – SPD Indigenous Children
21
In respect to specific factors that would need to be addressed should a national program be
launched, an issue identified through teacher feedback was lack of compliance with training
due to disinterest in the LiSN & Learn program with repeated use. Some modifications to the
software to make the games more engaging would help to alleviate this problem.
It was also noted that some target words required additional familiarisation following period
of absence such as school holidays, for example the verbs played, skipped and hopped. These
words could be highlighted on the flash cards and this issue could be noted in training packs
for teachers.
Limitations of the Study and Potential Solutions
As noted in the results section, three children who were suspected of having ear infections
were not undertaking the daily calibration procedure required to adjust LiSN & Learn output
levels. The children simply set the calibration slider bar to the same level each day, rather
than actually listening to, and adjusting the level of the reference tone. Thus it is probable that
the output levels in the headphones were inadequate during the period of infection. In the
case of these children, once the supervisor instructed these participants to “blow their noses”
before each test and also assisted in the calibration process the issue resolved, and
performance on the LiSN & Learn improved linearly. However, this issue highlights the fact
that audiometric and immittance data at the beginning and end of the study offer only limited
information on how a conductive disorder was potentially impacting the children overall and
particularly during training.
The calibration process could be improved by replacing the slider bar measurement with a
procedure whereby the listener selects on an object on the computer screen when he or she
Cameron et al – SPD Indigenous Children
22
perceives a tone. In this adaptive method, the reference signal becomes louder or softer
depending on the child’s response. There is far less possibility of the child faking or ignoring
the daily calibration procedure using this method.
Regardless of upgrading the software to improve the calibration procedure, it is still
imperative that the child’s performance is monitored daily to ensure that unexpectedly poorer
results on the LiSN & Learn is not the result of a pervasive middle ear infection over the
course of training, and that divergence from linear improvements is reported to the researcher
or professional overseeing the training. Following confirmation of a serious ear infection the
training can be suspended until the child is well enough to continue with the program. Of
course, unexpectedly poor performance on the LiSN & Learn on any particular day could be
due to any number of contributing factors in any population, including fatigue or distraction,
although as the incidence of chronic otitis media is so prevalent in the Indigenous Australian
community that researchers and professional and supervising teachers should be particularly
mindful of this factor during training. Effective communication of the results and limitations
of the current study to those involved in future studies or community programs with
Indigenous Australian will be necessary to minimize issues such as those associated with
middle ear infection on performance.
Conclusion
There is a high prevalence of SPD in the Indigenous Australian population. LiSN & Learn
training has the potential to remediate SPD in this population and is considered a beneficial
intervention by teachers, however improvement in spatial processing is dependent on
compliance with the training protocols. In any future program to assess and remediate
Indigenous Australian children for SPD school principals, teachers and supervisors should be
Cameron et al – SPD Indigenous Children
23
provided with the results of this study in respect to the relationship between training and
improvements in spatial processing ability so that realistic expectations of training outcomes
are ensured and game completion encouraged. Additionally, daily monitoring of LiSN &
Learn performance and calibration procedures may ensure that mild temporary hearing
threshold shifts do not impact severely on day-to-day performance and overall outcomes.
Acknowledgements
The authors would like to acknowledge the financial support of the Commonwealth
Department of Health and Ageing. The authors would also like to thank the principals,
teachers and students of the schools in Kempsey NSW who participated in this study. We
would also like to thank Mr Mark Seeto for assistance with statistics.
Declaration of Interest: This research was funded by Australian Hearing. The authors would
like to disclose that the LiSN-S test described in this paper is distributed under license by
Phonak Communications AG. The LiSN & Learn auditory training software described in this
article is distributed by the National Acoustic Laboratories. Financial returns from the sale of
the LiSN-S and the LiSN & Learn benefit the National Acoustic Laboratories and Dr
Cameron. This has in no way influenced the research reported in this article.
Cameron et al – SPD Indigenous Children
24
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Figure Legends
Figure 1. The four subtests of the LiSN-S test, and the three difference scores (advantage
measures) that can be derived from them. The target speech, T, always comes from the front,
whereas the two distracter stories, D1 and D2, come from the front or the sides, in different
conditions. D1 and D2 can be the same voice as T or different voices.
Figure 2. Image of a LiSN & Learn training game.
Figure 3. Histogram showing performance on the LiSN-S as measured by the pattern
measure, expressed as a Z-score, for the 144 participants in the study.
Figure 4. Individual improvement in SRT in dB on LiSN & Learn over time, expressed as a
five-day running average, for each of the nine participants who took part in the auditory
training study.
Figure 5. Pre- and post-training performance on the LiSN-S pattern score, expressed as a Zscore, for the nine participants in the LiSN & Learn auditory training study. Error bars
represent 95 per cent confidence intervals.
Figure 6. Scatterplot of positive relationship between total number of LiSN & Learn games
played and post-training improvement on LiSN-S as measured by the pattern Z-score.
Regression bands, bounded by dotted lines, represent 95 per cent confidence intervals.
Cameron et al – SPD Indigenous Children
30
Figure 7. Performance on the individual LiSN-S SRT and advantage measures pre- and postfor the nine children in the LiSN & Learn study. Performance is expressed in population
standard deviation units from the mean. Error bars represent 95 per cent confidence intervals.