Pupil dilation as a measure of cognitive effort
in the LiSN-S test
Sarosh Kapadia, David Cornish, Sean Fumberger, Joshua Margach, Tobias Loetscher*
Flinders University, Adelaide, Australia; *University of South Australia, Adelaide, Australia
Abstract
Results and conclusions
The measurement of cognitive effort during listening tasks is currently of great
interest within audiology. Pupillometry is experiencing a resurgence as an index of
such effort. Pupillometry may also help address fundamental questions around the
nature of auditory processing and its interaction with cognition. We present data
on pupil dilation during completion of the Listening in Spatialized Noise-Sentences
(LiSN-S) test, demonstrating the capacity of pupillometry to differentiate cognitive
effort in auditory tasks of differing degrees of difficulty.
Figure 2 shows pupil dilation as a function of time for each of the four LiSN-S
conditions, averaged across all 20 participants. The figure shows a trend for
progressively greater dilation as task difficulty increased.
The measurement of cognitive effort during auditory processing (AP) tasks may
help address fundamental questions around the nature of AP and its interaction
with cognition. The use of pupil dilation as a measure of cognitive effort has gained
renewed interest in recent years, due in part to the ready availability of pupillometric
equipment. The bulk of current research in the area involves specialised, inhouse listening tasks (developed by the relevant research laboratory), rather than
commercially available AP tests that are routinely used in the clinic. Ambient
illumination levels are also often carefully controlled, e.g. individualised for each
participant, in conducting such research.
Different voice, 90
Same voice, 90
Different voice, 0
Same voice, 0
0.25
pupil dilation (mm)
Introduction
0.3
0.2
0.15
0.1
Target sentence onset
0.05
0
This study is a preliminary investigation into the use of pupil dilation as a measure of
cognitive effort involved in undertaking a commercially available, widely used AP test,
the Listening in Spatialized Noise-Sentences (LiSN-S) test, in a clinical setting. The LiSN-S
is a “target in competition” speech test. It employs a number of sub-tests that either do
or do not provide talker and spatial cues that assist in target speech discrimination. The
sub-tests therefore present inherently different degrees of task difficulty.
-0.05
0
1
2
3
4
5
time (s)
6
7
8
9
10
Figure 2. Pupil dilation as a function of time for each of the four LiSN-S
conditions, averaged across all 20 participants. Traces have been smoothed
The objectives of the study were:
using a 20-point moving average filter, and dilation is plotted relative to
pupil diameter at target sentence onset. A marked increase in pupil diameter,
• To assess pupil dilation as a measure of cognitive effort during the LiSN-S test
commencing approximately 0.5 s after target onset, is evident, as well as a trend
The result
of by
thismanipulating
condition is called
child’s “high cue speech reception threshold”,
• To investigate the effect of task difficulty
(varied
talkerthe
and
for progressively greater dilation from the easiest (Different voice, 90°) through
or “high cue SRT”.
spatial cues) on any such pupillary changes
to the most difficult (Same voice, 0°) task condition.
• To investigate the effect of ambient lighting levels on the task-evoked pupillary
changes
Figure 3 shows the mean pupil dilation in the five-second window following
stimulus onset, for all four LiSN-S conditions. Repeated measures ANOVA showed a
significant effect of test condition on mean pupil dilation, with polynomial contrasts
demonstrating a significant linear increase in dilation across the four test conditions.
Post-hoc tests indicated significant differences between LiSN-S Conditions 1 and 4
Data
are
presented
from
20
otologically
normal
young
adults
with
no
reported
h cue speech reception threshold”,
and between Conditions 2 and 4.
listening, speech, language, attentional or learning difficulties.
Methods
mean pupil dilation (mm)
Participants undertook the LiSN-S test as per standard administration (see Figure 1),
0.2
with simultaneous recording of pupil diameter using the Senso Motoric Instruments
(SMI) ETG 2.0 system. In each participant, pupil diameter was averaged across 10
sentences (trials) around the speech reception
threshold2:
forSame
eachVoice
test condition.
Ten
16.5.2 Condition
±90°
0.16
participants
undertook
low cue
(15two,
lux),
and
ten under
relatively
high of the same voice as the target speech,
The
result of this
condition testing
is called in
therelatively
child’s
speech
reception
threshold”,
In “high
condition
the
competing
speech
is composed
lux),
levels.
or(46
“high
cueillumination
SRT”.
and again comes from the left and right.
0.12
16.5.4 Condition 4: Same Voice 0° (Low cue SRT)
In condition four, the competing speech uses the same
from in front of the child – the same direction as the t
This fourth condition is the most difficult of the four a
and the target and competing speech is very similar. T
the child’s low cue speech reception threshold or “low
16.5.4 Condition 4: Same Voice 0° (Low cue SRT)
0.08
In condition four, the competing speech uses the same voice as the target speech and comes
from in front of the child – the same direction as the target speech.
the same voice as the target speech,
0.04
This fourth condition is the most difficult of the four as there are no spatial cues available
and the target and competing speech is very similar. The result of this test is referred to as
Same
voice
±90 Condition
Different voices ±90 Condition
Speech
signal
Speech signal
the child’s low
cue
speech
reception
threshold
or “low cue16.5.4
SRT“. Condition
4: Same Voice 0° (Low cue SRT)
0
Noise from same voice
Noise from different voices
2
1
voice, 90 speech
Same
90 voice Diff
voice,
0 speechSame
voice, 0
In condition four, Diff
the competing
usesvoice,
the same
as the
target
and comes
from in front of the child – the same directionLiSN-S
as theCondition
target speech.
16.5.2 Condition 2: Same Voice ±90°
16.5.3 Condition 3: Different Voices 0°
In condition two, the competing speech is composed
the samethree,
This
fourth
condition
isthe
the
most difficult
the16.6
four as
there
are no
spatial
cues
available
voicethe
as the
target speech,
LiSN-S
Advantage
Measures
Withofcondition
competing
speech is composed of
different
target
Figure
3. voices
Meanthan
pupil
dilation
in theoffive-second
window
following
stimulus
the
target
and competing
is very similar.
Thedistracting
result
this
test from
is referred
to asto the sides
and again comes from the left and right.
Moving
voices
the front
speech and comes from the front – the same direction asand
the
target
speech.
onset,
averaged
across allspeech
participants,
for
each
of
theoffour
LiSN-S
conditions.
the
child’s
low
cue speech
reception
threshold
orcues.
“low How
cueThere
SRT“.
muchwere
an individual
child benefits from
Error
bars
indicate
standard
errors
of the
mean.
significant
differences in mean dilation between LiSN-S
Condition
(Different
voice,between
90°) conditi
by measuring
the 1difference
in scores
and Condition 4 (Same voice, 0°) and between Condition 2 (Same voice, 90°) and
Condition 4 (Same voice, 0°).
Same voice 0 Condition
Different voices 0 Condition
Speech signal
Speech signal
This “spatial advantage” is calculated automatically
Noise from same voice
Noise from different voices
4
3
indicator of auditory processing disorder.
Repeated measures ANOVA also showed no significant effect of ambient lighting
Figure 1. The LiSN-S test. Target speech is presented in the presence of competing
d of
different
voices than
the target
16.5.4
Condition
4: Same
Voice 0° (Low cue 16.6
SRT) LiSN-S Advantage Measures
diagnosed with
APD score
very poorly in t
level used (15 or 46 lux) on mean dilation, Children
and no significant
interaction
between
speech in four conditions (as labelled), which either do or do not provide talker and
Moving
distracting
voices
from
the
front
to
the
sides
allows
a
child
to
make
use
of
spatial
asInthe
target
speech.
condition
four,
the
competing
speech
uses
the
same
voice
as
the
target
speech
and
comes
ambient
lighting
level
and
test
condition.
spatial cues that assist in target discrimination. Normative data indicate progressively
HowCondition
much
child 4.benefits
movement is easily calculated,
from
in fronttask
of the
child – the
sameperformance)
direction ascues.
thefrom
target
speech.an 1individual
greater
difficulty
(poorer
to Condition
(Figurefrom thisThese
findings illustrate the potential of pupillometry as a non-intrusive, increasingly
by measuring
the Australia.)
difference in scores between conditions 2 and 4.
used with permission of National Acoustic
Laboratories,
affordable tool for the measurement of cognitive effort in the audiology clinic.
This fourth condition is the most difficult of the four as there are no spatial cues available
34
This The
“spatial
by LiSN-S and is a highly sensitive
and theCondition
target and3:
competing
very similar.
resultadvantage”
of this testisiscalculated
referred toautomatically
as
16.5.3
Differentspeech
Voicesis0°
www.flinders.edu.au
auditoryvoices
processing
disorder.
the child’s
low cue
speech
reception speech
threshold
orindicator
“low cue
16.6 LiSN-S Advantage Measures
With
condition
three,
the competing
is composed
ofofSRT“.
different
than the
target
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