(Cameron et al 2014) IJA - National Acoustic Laboratories

International Journal of Audiology 2014; Early Online: 1–10
Original Article
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Prevalence and remediation of spatial processing disorder (SPD)
in Indigenous children in regional Australia
Sharon Cameron, Harvey Dillon, Helen Glyde, Sujita Kanthan & Anna Kania
National Acoustic Laboratories, Sydney, Australia
Abstract
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%) 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 postintervention. 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.
Key Words: Spatial processing disorder; chronic otitis media; deficit-specific auditory training
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, 2013; 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 signalto-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 –
Sentences 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 (Brown et al, 2010; Cameron
et al, 2011). In order for the LiSN-S to be used with the hearingimpaired 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
Correspondence: Sharon Cameron, National Acoustic Laboratories, Australian Hearing Hub, 16 University Avenue, Macquarie University, Sydney, NSW 2109, Australia.
E-mail: [email protected]
(Received 6 June 2013; accepted 26 November 2013)
ISSN 1499-2027 print/ISSN 1708-8186 online © 2014 British Society of Audiology, International Society of Audiology, and Nordic Audiological Society
DOI: 10.3109/14992027.2013.871388
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S. Cameron et al.
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Abbreviations
4FAHL
ACMS
AEO
CANS
CAPD
COM
GLM
HRTF
Leq
LIFE
LiSN-S
NAL-RP
NSW
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
New South Wales
Prescribed gain amplifier
Signal-to-noise ratio
Spatial processing disorder
Speech reception threshold
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
participants’ SRTs on the LiSN & Learn improved by approximately
10 dB over the course of the training. Improvements on behavioural
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.
tests were in line with self-report, parent and teacher ratings of listening ability post training. For a comprehensive review see Cameron
and Dillon (2013).
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% 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% 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%
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 of 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, 2013). That is, the deprivation
may lead to a reduction in the number of synapses available to assist
in binaural interaction. It is possible 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 non-Indigenous 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
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.
SPD Indigenous Children
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.
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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, New South Wales, 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 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
0.5, 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) ⱖ 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 (0.5, 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
3
levels were recorded. The procedure used, prior to testing, to calculate the LiSN-S permissible noise levels is detailed in Supplementary
Appendix A to be found online at http://informahealthcare.com/
doi/abs/10.3109/14992027.2013.871388.
Children who were diagnosed as having SPD were retested 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 the 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 0.5 to 4 kHz. 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 pre-determined level by the LiSN-S software in order to achieve
pre-designated signal levels, 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. ⫹90° 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 0°, same voice at ⫾90°, different voices at 0°
and different voices at ⫾90°. The SNR was adjusted adaptively in
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S. Cameron et al.
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% of words in a sentence correct, and increased
by 2 dB if he or she scored less than 50% of words correct. The SNR
was not adjusted if a response of exactly 50% correct was recorded
(for example, 3 out of 6 words correctly identified). A minimum
of five sentences were provided as practice, however, practice continued until one upward reversal in performance (i.e. the sentence
score dropped below 50% of words correct) was recorded.
Testing ceased in a particular condition when the listener had
either (1) completed the entire 30 sentences in any one condition;
or (2) 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 minutes 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).
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 et al, 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 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 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 and
the distracter stories emanated from ⫹90° and ⫺90° 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, forcedchoice, 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
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SPD Indigenous Children
5
Figure 2. Image of a LiSN & Learn training game.
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 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 non-training
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
Analyses were performed with Statistica 10.1.
Prevalence of SPD
Fifteen of the 144 participants, or 10.4% of the study sample, presented with a mild conductive hearing loss (⬎ 20 dB at 0.5, 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 ShapiroWilk 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% 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
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S. Cameron et al.
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.
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 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
Table 1. Pre- and post-training audiological profiles and LiSN-S
results for the nine children who took part in the LiSN & Learn
auditory training study. Note that bilateral hearing was screened
screened to 20 dB HL, as reflected in the LE and RE 4FAHL.
Pre-training
Tympanogram
type
Post-training
4FAHL
ID
Age
LE
RE
LE
326
408
409
418
518
523
524
609
622
8.6
6.3
7.9
6.1
8.7
6.7
6.4
7.5
6.3
B
B
B
Cs
As
A
A
A
B
B
Ad
B
C
B
C
A
A
B
29
21
ⱕ 20
ⱕ 20
ⱕ 20
ⱕ 20
ⱕ 20
ⱕ 20
33
RE
Tympanogram
type
4FAHL
LE
RE
LE
RE
33 A
18 Ad
ⱕ 20 B
ⱕ 20 C
ⱕ 20 A
ⱕ 20 B
ⱕ 20 A
ⱕ 20 A
34 A
C
B
As
As
A
C
A
A
A
ⱕ 20
ⱕ 20
ⱕ 20
ⱕ 20
ⱕ 20
16
ⱕ 20
ⱕ 20
ⱕ 20
21
ⱕ 20
ⱕ 20
ⱕ 20
ⱕ 20
23
ⱕ 20
ⱕ 20
ⱕ 20
Note: LE ⫽ left ear; RE ⫽ right ear; 4FAHL ⫽ four frequency average
hearing loss.
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 Z-score 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 post-training 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% confidence intervals, there was more
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 posthoc 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.
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SPD Indigenous Children
7
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.
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 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 Supplementary
Appendix B to be found online at http://informa healthcare.com/doi/
abs/10.3109/14992027.2013.871388. 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
Table 2. Pre- and post-training performance on the LiSN-S pattern score, expressed as a Z-score, for the nine participants in the LiSN &
Learn auditory training study, together with number of LiSN & Learn games played, and LIFE - ‘Teacher Appraisal of Listening Difficulty’
questionnaire results. LiSN-S pattern Z-scores marked with an asterisk are still outside normal limits (i.e. ⬍ ⫺1.96 SD) post-training. Note
for the LIFE a total appraisal score of 35 represents strong positive change and that the intervention was highly beneficial, 0 represents no
change, and ⫺35 suggests the intervention was highly unfavourable.
ID
Age
LiSN & Learn
Games played
Pre-training
LiSN-S pattern
Z-score
SD
326
408
409
418
518
523
524
609
622
8.6
6.3
7.9
6.1
8.7
6.7
6.4
7.5
6.3
98
42
25
32
82
90
90
59
63
⫺2.2
⫺2.7
⫺2.6
⫺2.4
⫺2.2
⫺3.0
⫺3.2
⫺2.5
⫺2.2
Post-training
LiSN-S pattern
Z-score
SD
⫺0.5
⫺3.4∗
⫺4.6∗
⫺5.6∗
⫺0.8
⫺2.3∗
0.9
0.9
0.5
Improvement in
LiSN-S pattern
Z-score
SD
1.7
⫺0.7
⫺1.9
⫺3.2
1.4
0.7
4.1
3.4
2.6
LIFE Teacher
appraisal
Total
score
11
35
35
13
25
31
33
13
20
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8
S. Cameron et al.
Figure 5. Pre- and post-training performance on the LiSN-S pattern score, expressed as a Z-score, for the nine participants in the LiSN &
Learn auditory training study. Error bars represent 95% confidence intervals.
(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%.
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 LiSN-S performance improved by nearly one
population standard deviation. However, LiSN-S performance was
variable and significantly related to the number of LiSN & Learn
training 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
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% confidence intervals.
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SPD Indigenous Children
9
Figure 7. Performance on the individual LiSN-S SRT and advantage measures pre- and post- for the nine children in the LiSN & Learn
study. Performance is expressed in population standard deviation units from the mean. Error bars represent 95% confidence intervals.
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 Supplementary Appendix B to
be found online at http://informahealthcare.com/doi/abs/10.3109/
14992027.2013.871388 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 posttraining, 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.
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
familiarization following a 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 training session 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 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 are 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
10
S. Cameron et al.
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.
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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 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 dayto-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.
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