The effect of visual perceptual load on auditory awareness in
Autism Spectrum Disorder
Julian Tillmann & Dr John Swettenham
Model of selective attention - Lavie’s perceptual load theory of attention and cognitive
control:
The extent to which task-irrelevant stimuli are processed depends on the
perceptual load of a task (i.e. amount of task-relevant information such as the number
of items in a search display or perceptual requirements of a task)
-
Assumptions:
(1) Perception is a limited-capacity process
(2) Stimuli are automatically processed until perceptual capacity is reached
Tasks of low perceptual load: Any spare capacity after processing task-relevant stimuli
will automatically „spill over‟ into processing of task-irrelevant distractor stimuli
Tasks of high perceptual load: Engage full perceptual capacity, leaving little or no room for
distractor processing
Role of perceptual load in Autism Spectrum Disorder:
Exp. 1: Percentage of typically developing children reporting awareness of the auditory
stimulus according to year group (Y1 vs. Y5)
% of participants reporting awareness
The ability to prioritise certain aspects of the environment and ignore others, which is referred to
as selective attention, seems to operate differently in ASD, with individuals demonstrating both
strengths and weaknesses on some behavioural tasks
80%
Year 1
70%
60%
Year 5
50%
40%
30%
20%
10%
0%
Low Load
High Load
- Children in the year 5 age group were significantly more likely to notice the auditory stimulus
than children in the year 1 age group (p= .003)
- Awareness rates were significantly higher in the low perceptual load version than in the high
perceptual load for year 5 children, (p= .016), but not for year 1 children
- As visual perceptual load increases, adults with ASD continue to process task-irrelevant
visual stimuli whereas control participants do not
Currently not known whether the same applies for contexts involving crossmodal selective attention
In neurotypical adults, some evidence suggests that high visual perceptual load reduces
awareness of an auditory stimulus using an inattentional deafness paradigm (Macdonald &
Lavie, 2011)
Predictions
•
•
Typically developing (TD) children show reduced awareness of an auditory stimulus
in a high perceptual load task compared to a low perceptual load task
Children diagnosed with ASD show greater awareness of an auditory stimulus
compared to controls at high levels of perceptual load
Children in Year 1
Children in Year 5
(6y 1m, N= 44)
(10y 2m, N= 60)
Experiment 2:
Effect of visual perceptual load on
auditory awareness in ASD children
TD children (10y 2m, N= 44)
ASD children (10y 4m, N= 26)
High perceptual load:
Low perceptual load:
TD
70%
60%
ASD
50%
40%
30%
20%
10%
0%
High Load
- As predicted by load theory, TD children were more likely to notice the auditory stimulus in the
low visual load vs. high visual load task, p= . 005
- This was not the case however for children with ASD, who demonstrated similar detection
rates across perceptual load conditions (p= .899), yet reported greater awareness than
controls in the high perceptual load task, p= .004
Development of perceptual capacity in TD children
Stimuli
Participants performed in
either a high-and low
perceptual load version of
a line discrimination task
80%
Low Load
Participants
Experiment 1:
Development of perceptual capacity in
TD children
% of participants reporting awareness
- These findings may reflect an increased perceptual capacity in ASD (Remington et al.,
2009, 2012; Swettenham et al., in press).
Exp. 2: Percentage of children reporting awareness of the auditory stimulus according to
diagnostic group (TD vs. ASD)
The results from experiment 1 extend the findings by Macdonald & Lavie (2011) to children
• Awareness of an unexpected auditory stimulus was modulated by the visual perceptual
load of a primary task
- This implies that attentional resources are shared between sensory modalities and
performing a visual task can result in not noticing an otherwise clearly audible sound
• However, a load-dependent modulation of awareness was only reported in older children,
whereas younger children reported low awareness rates across perceptual load conditions
- Given that perceptual capacity was already exhausted under low levels of perceptual
load in younger children, the findings suggest that perceptual capacity is subject to
developmental changes across the lifespan, i.e. it increases with age
Procedure
Trials 1-6
Trials 7-8 (Critical trial + control)
Effect of visual perceptual load on auditory awareness in ASD children
1500ms
1500ms
96ms
time
96ms
110ms
time
110ms
496ms
496ms
The finding that children with ASD were more likely to notice an auditory stimulus under high
visual perceptual load than controls suggests that they had resources “left over” to attend to the
additional stimulus
• Extends recent findings of an increased perceptual capacity in ASD on visual selective
attention tasks (Remington et al. 2009, 2012; Swettenham et al., in press) to contexts of
cross-modal selective attention
• In particular, ASD is characterised by an increased perceptual capacity that operates
across sensory modalities and allows individuals with ASD to process more information at
any one time
110ms
Participants indicated on each trial which line is longest (line going up vs. line going down). On
the critical trial, an unexpected auditory stimulus (70db) was played concurrently with presenting
the cross and participants were asked: “did you notice anything else?”. On a subsequent control
trial, participants were told to ignore the cross stimulus. Only those participants who
successfully identified the auditory stimulus on the control trial were included in further analyses
• Our findings also indicate that an increased perceptual capacity is present from childhood
and hence might be a core characteristic of this disorder
Key references
Lavie, N. (1995) Perceptual load as a necessary condition for selective attention. Journal of Experimental Psychology: Human Perception and Performance, 21, 451–468.
Macdonald, J. S. P., & Lavie, N. (2011). Visual perceptual load induces inattentional deafness. Attention Perception & Psychophysics, 73(6), 1780-1789.
Remington, A., Swettenham, J., Campbell, R., & Coleman, M. (2009). Selective attention and perceptual load in autism spectrum disorder. Psychological Science, 20(11), 1388-1393.