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BA Thesis English Language and Culture, Utrecht University.
Jolanda van Amstel
Student number: 3767086
Griend 38-09
8225 TR Lelystad
Supervisor: K. Sebregts
Second reader: A. Kerkhoff
Aug. 2014
7410 words
Speech Perception within the Framework of Asperger Syndrome and ASD
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Table of Contents
1. Introduction ………………………………………………………………………3
2. Linguistic background ……………………………………………………………4
2.1. Speech perception ………………………………………………………..4
2.2. Language acquisition …………………………………………………….8
3. Language and perception within the frame of Autism and Asperger syndrome….11
3.1. Early observations and diagnostics ……………………………………...11
3.2. Current theories and research on auditory processing ………………..…13
3.3. Speech perception …………………………………………………….…16
3.4. Sensory Sensitivity ………………………………………………………19
3.5. Language Delay …………………………………………………….……21
4. Conclusion ……………………………………………………………………..…26
Works cited ……………………………………………………………………….28
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1. Introduction
Natural, everyday speech is extremely complex, and yet most people have no problem parsing
long strings of phonemes into meaningful units and understand the message they convey. Within
the field of linguistics, researching speech perception continues to be a challenge. There are
different theories that contribute to the field, though many of these theories continue to be
researched and questioned, which includes research on hearing-impaired and deaf subjects and
what effects their impairment have on their language perception, but also how their impairment
might affect or have affected their language acquisition during infancy (Harley, 2010; Fromkin,
Hyams & Rodman, 2011). Another field to consider for research on speech perception may be
Autism Spectrum Disorders (ASD), and specifically Asperger Syndrome. ASD is not associated
with any hearing deficits, but is characterised by sensory difficulties, which include auditory
perception and processing issues (Attwood, 1998; O’Conner, 2012; DuCharme & Gullotta,
2013). It may prove insightful to attempt to describe and define these perception issues in more
detail from a linguistic point of view, while also considering the potential contribution of these
differences in perception to the field of linguistic research in general.
Language plays a key role within the fields of Autism Spectrum Disorders (ASD) and
Asperger Syndrome (AS). While ASD is strongly characterised by language-specific difficulties
and deviations, AS is a specific label at the higher-functioning end of the autism spectrum and
“characterized by an absence of clinically significant … language delay” (American Psychiatric
Association, cited in Bennett et al., 2008, p. 616). Since many of the language-specific issues are
largely observed through language use within social contexts, most of the research and
diagnostics surrounding AS focus on pragmatics and the social aspects of language (O’Conner,
2012). However, another characteristic associated with AS, and with ASD in general, is sensory
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sensitivity (Asperger, 1944; Attwood, 1998; DuCharme & Gullotta, 2013). Though this sensory
sensitivity was identified as a diagnostic criterion early on, it has been left out of most research
and studies up until very recently (Pellicano, 2013). Considering the complexity of speech and
speech perception, sensory sensitivity may to a degree affect speech perception. In turn,
difficulties with language perception may have larger implications for language acquisition.
Firstly, language and speech perception will be discussed, including multiple theories
which illustrate the complexity of natural speech and how people are able to process it.
Additionally, the role of language perception in language acquisition theories will be described.
This will be followed by a brief summary of the role of language within the framework of ASD
research and diagnostics, followed by current theories on auditory perception in ASD. A more
detailed description of the suggested auditory perception issues will be provided next. The
potential role of perceptual deviation in the delayed language acquisition process of AS and ASD
individuals will also be discussed. Describing these perceptual difficulties in linguistic terms will
highlight the potential issues that individuals with AS and ASD might have with regards to
speech perception. In turn, the perceptual difficulties associated with AS and ASD may illustrate
the complexity of speech perception and processing.
2. Linguistic Background.
2.1.Speech perception
Despite the acoustic complexity of natural speech and the rate at which it is generally
produced, real-time speech processing and comprehension generally happens at an equally
incredible speed. In order to facilitate fast and accurate speech comprehension, people use both
bottom-up and top-down processing. Bottom-up processing refers to the use of input, and word
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recognition is partially based on which phonemes are perceived. Top-down driven processing
refers to speech segmentation based on linguistic knowledge (Ashcraft & Radvansky, 2010, p.
338-339; Fromkin et al., 2011, p. 381-382). People can use their lexical knowledge to facilitate
the quick parsing of strings of phonemes into recognisable words. Additionally, syntactic
knowledge can be used to recognise the grammatical structure of a sentence, and anticipate the
syntactic category of a word based on a word previously perceived (Fromkin et al., 2011, p. 384385). For example, if the word ‘the’ is perceived, this would allow for the assumption that the
following word will be a noun or noun phrase, thus limiting the number of possible lexical
options. Though these processes of speech processing are not entirely fool proof and can
occasionally allow for the misinterpretation of ambiguous words or sentences (Fromkin et al.,
2011, p. 385), they are generally considered to be fast and effective enough to facilitate effective
comprehension and communication.
Next to the fast rate of speech processing, the variable nature of individual phonemes in
natural speech poses a considerable challenge for research regarding speech perception and
processing. In natural speech, phonemes are rarely articulated the same way every time, and can
be affected by individual articulatory differences, which may be caused by voice pitch, accent
and the gender or biological sex of the speaker, as well as contextual, phonological differences.
Co-articulation causes a particular phoneme to be affected by the previous or following
phoneme, and assimilation can cause a phoneme to be reduced or even left unpronounced
entirely. Despite these seemingly challenging circumstances, most people seem perfectly capable
of perceiving speech, and may even be largely unaware of these articulatory variations. The most
commonly accepted theory as to how people manage to perceive phonemes accurately enough to
differentiate between them, and thus deriving their specific meaning, is categorical perception.
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Categorical perception supposes that even though a specific phoneme or syllable may closely
resemble another, e.g. ba- and ga-, these will always be perceived distinctly as ba- or ga-.
Though there may be many variations in the pronunciations of sounds, people’s categorical
perception allows for the labelling of these sounds according to distinct categories (Harley, 2010,
p. 149; Wolfe, Kluender & Levi, 2012, p. 315-316).
However, categorical perception as used in experiments has recently been called into
question as an effective method. Schouten, Gerrits and Van Hessen (2003) considered several
factors which may influence the results of experiments using categorical perception as their
basis. Stimuli used in research can be more or less natural-sounding, making these more or less
suitable as representation of speech perception in real-life settings. More importantly, however, it
appears that there is a difference between classifying phonemes in different categories, as
opposed to actually discriminating between phonemes. Schouten et al. argue that if “… the
nature of the task compels subjects to use a labelling strategy, categorical perception will be
pretty much a foregone conclusion” (p. 77). This suggests that many of the experimental set-ups
used to investigate categorical perception actually encouraged subjects to use categorical
labelling as a strategy, creating a bias. An unbiased experiment designed by Schouten et al.
showed that without asking subjects to label specific stimuli, and to only discriminate one
deviant phoneme from a set of four stimuli, resulted in little to no correlation between the
discrimination of stimulus and the categorical label of the stimuli. Supposedly, if categorical
perception is a largely subconscious process used to parse natural speech, then any task
specifically asking for categorisation is inherently flawed. Thus natural speech perception is
possibly not as clear-cut as some authors would claim. Considering the wide use of and reliance
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on categorical perception in research, this may have severe implications on the reliability of said
research.
In addition to auditory input, part of speech perception may also rely in visual input. One
theory that suggests this is referred to as the motor theory of speech perception (Ashcraft &
Radvansky, 2010). In general, this theory supposes that part of our social perception relies on the
largely subconscious knowledge we have of our own motor functions and movement, which
helps us interpret other people’s movement. Specifically regarding speech perception, the visual
cues provided by the articulation of a speaker should provide additional information as to what is
being said, especially when the sound of a person’s speech is not fully perceived. This can,
however, also lead to misperceptions. A well-known perceptual illusion is the McGurk effect
(Wolfe et al., 2012, p.316), in which the auditory perception is affected by visual input. In a
laboratory set-up, for example, when subjects are presented with the auditory stimulus ‘ba’, and
simultaneously are presented with the visual stimulus of a person saying ‘ga’, the subjects may
report to perceive the auditory stimulus as ‘da’ or ‘ga’, rather than the ‘ba’ it would be perceived
as without the visual input. This suggests that the integration of auditory and visual input can
affect speech perception.
Several theories describing speech perception also consider the top-down process of
using context. People can use the semantic and even pragmatic context of words and sentences to
facilitate speech processing and resolve potential ambiguities or abnormalities in a speech signal.
Many studies have focused on phoneme restoration (Fromkin et al., 2011; Wolfe et al., 2012). In
these experiments, listeners are presented with a spoken sentence with one or several phonemes
have been taken out and replaced by a neutral noise like a cough or buzz, for example: “The *eel
was on the orange”. Though the /p/ is not actually in the sentence, listeners are likely to report
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that they hear ‘peel’, rather than ‘eel’ (Ashcraft, 2010, p. 339). They use their semantic
knowledge to anticipate which words that are more or less likely to appear in a specific context,
and in this context ‘peel’ would be more likely than ‘eel’, ‘feel’, or any similar word. Part of
people’s ability to anticipate the likelihood of specific words and sentences to occur within a
specific context also comes from the general experience people have when it comes to listening
to speech (Wolfe et al., 2012).
Speech processing relies on both bottom-up and top-down processing, both of which
happen on a largely subconscious level. A key point to consider is that people acquire most of
their linguistic knowledge and much of their experience with listening during infancy. Infants
need exposure to language, but perceptual issues may interfere with this process.
2.2. Language acquisition
There are two distinctly different views within linguistics when it comes to language
acquisition. Empiricist views are largely based on a blank slate approach, and suppose that the
acquisition of language is no different from learning other cognitive skills (Harley, 2010, p. 25).
In contrast, nativism views on language acquisition suggest the existence of some innate
knowledge that specifically facilitates children’s language acquisition. A strong argument in
favour of nativist theories is that children cannot be exposed to every variable in their native
language nor are they given explicit instructions regarding syntax, and yet they acquire language
earlier than most other cognitive skills. The innate ability for language acquisition is called
Universal Grammar (UG), and the mechanism that facilitates language acquisition is generally
referred to as a Language Acquisition Device (LAD) (O’Grady, 1997; Fromkin et al., 2011, p.
330). This device is largely associated with syntactic acquisition, specifically considering that
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people continue to learn new lexical entries well after their childhood years. In comparison, if a
child does not receive enough input during the supposed critical period of language acquisition,
his or her syntactic development may be delayed or permanently limited (Harley, 2010, p. 77-81;
Fromkin et al., 2011, p. 22).
When considering language perception theories, the question may be raised as to how
infants can segment incoming speech, as they have yet to acquire the linguistic knowledge
necessary to process natural speech. Children acquire their language in sequential stages, and
most theories consider bootstrapping as a main strategy. Bootstrapping refers to the use of
previously gained knowledge to acquire more knowledge (Harley, 2010, p. 55; Fromkin et al.,
2011, p. 337-338). The first stage for language acquisition focuses on the prosodic characteristics
of the child’s native language, starting with rhythm. Even prenatal infants have been observed,
though heartbeat recordings, to respond to speech signals changing from one language to another
(Harley, 2010, p. 51). After being acquainted with the specific rhythm of a language, a child may
start picking up on other prosodic speech characteristics, such as intonation and word stress
patterns. This includes the acquisition of the specific phonemes of the child’s native language.
The acquisition of the prosodic and phonetic characteristics of a language in turn allow for the
recognition of syllables and word boundaries. At the same time, the LAD facilitates acquisition
of syntactic knowledge based on sentence patterns and word combinations. Once a child acquires
the ability to parse separate words from a speech signal, parsing new words becomes much
easier. This is generally referred to as lexical bootstrapping (Fromkin et al., 2011, p. 343). Early
stages in language acquisitions facilitate later stages, and it is suggested that these sequential
stages are very similar across different languages, and perhaps universal (Fromkin et al., 2011, p.
332).
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Another aspect of language acquisition is the role of mirror neurons. Mirror neurons have
been suggested to play an important role in social behaviour and language learning (Purves,
2013). These neurons, for example, enable people engaged in a conversation to subconsciously
adjust their body language to match that of their conversation partner. Similarly, mirror neurons
may allow people to closely imitate someone’s actions and skills, and thus learn to use such
actions and skills themselves. It is strongly suggested that imitation alone does not play a large
role in the language development of a child (Fromkin et al., 2011, p. 325). However, mirror
neurons allow children to imitate linguistic input they are exposed to, and actually learn the skills
necessary to use their linguistic knowledge. As mirror neurons are connected to learning in a
social context, this supports the notion that language acquisition also requires a social context.
Mere exposure to language is not enough. A direct social context is necessary to properly
facilitate language acquisition (Harley, 2010, p. 81).
It should be noted that language acquisition is not solely dependent on auditory input.
Children born deaf can acquire sign language in the same stages as children acquiring spoken
language (Fromkin et al., 2011, p. 355). However, their language development may be delayed if
a deaf child is not given the appropriate input: “Deaf children of hearing parents who are not
exposed to sign language from birth suffer a great handicap in acquiring language” (Fromkin et
al., 2011, p. 356). This stresses the importance of a child being exposed to the appropriate type
and amount of input. To compare, Autism Spectrum Disorders are generally associated with
sensory perception and processing difficulties, including auditory perception issues. There is
extensive research done to support theories of deviant sensory processing in ASD. These theories
on deviant auditory perception may also provide clues on how these perceptual difficulties may
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relate to the speech perception and language acquisition process of individuals with AS and
ASD.
3. Language and perception within the frame of Autism and Asperger syndrome
3.1. Early observations and diagnostics.
In his original paper in 1944, Hans Asperger set out to describe and document what he
considered to be “a particularly interesting and highly recognizable type of child” (p. 37). By
coining the label ‘autistic psychopathy’, he explicitly set this group of children apart from the
psychotic image observed in schizophrenia, with which autism was closely associated. Asperger
acknowledged that this syndrome, as a developmental disorder, manifests itself in early
childhood and persists throughout adulthood. By identifying children who showed atypical
behaviour and language use, he had the genuine intention to help these individuals to still live a
fulfilling life, despite potential social difficulties. Asperger himself, as well as Frith (1991),
acknowledged that despite clearly recognisable characteristics, there are many individual
differences between the cases described that suggest a strongly heterogeneous nature of this
particular group of people (Frith, 1991, p.3, 67).
Asperger’s initial observations were based on behaviour and social interaction. He
described children’s social behaviour, especially their eye-gaze in conversation. They showed
apparent aversion for eye contact. In conversations, this made it difficult to determine whether
their attention was directed to the speaker, somewhere else, or potentially more inwards to a
child’s own thoughts (p. 69). Additionally, when considering the lack of eye contact in a
conversation, there was uncertainty whether the speech produced by these children was directed
to a listener, or perhaps nowhere in particular (p.70). The research done regarding the social and
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behavioural aspects of AS and ASD and their relation to language is very extensive, but goes
well beyond the scope of this paper. This aspect will only be discussed to a very limited degree.
At the time of Asperger’s paper, the scientific field of linguistics was still in its infancy,
and thus any language-specific observations made by Asperger were also largely based on
behavioural observations. As language is an expressive and social function, the author noted
some abnormalities in the language of these individuals. Their voices may vary greatly in
volume and tone of voice, as well as intonation. Though considerably varied between
individuals, it was apparent that their speech sounded strangely unnatural. Asperger strongly
noted the social implications of atypical speech production, namely that “the language feels
unnatural, often like a caricature, which provokes ridicule in the native listener” (p. 70).
Another observed characteristic for many of these children involved sensory sensitivity.
They showed strong reactions to loud or strange noises and bright lights, but also certain items of
clothing and even smells. This did not appear to be consistent, and some individuals could be
more or less sensitive to stimuli over periods of time, suggesting both hyper- and hyposensitivity
(p.80). As Frith (1991) notes, this aspect has been widely described in autobiographical accounts
(p. 14). She also argues that, although these sensory difficulties were observed in early research,
the extent of these issues have not been included in much research (p. 80). Later studies and
research did provide insight in the deviant sensory processing of individuals with ASD disorders,
including auditory perception and processing.
The first two cases of ‘autistic psychopathy’ that Asperger (1944) described included
reports of some delayed development during infancy, including a delay in speech production.
Interestingly, though these children did not start speaking until the age of 18 to 24 months, their
speech quickly developed to being “exceptionally good [and] like a grown up” (p. 59, 65). As
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Frith (1991) explains, “[i]n almost all cases [of autism] language learning is delayed, and in
some cases language is never acquired at all…Deafness is often suspected but ruled out” (p. 3).
Asperger syndrome, specifically, is characterised by the delayed but eventual full development
of language (Attwood, 1998; DuCharme & Gullotta, 2013). This may be an interesting topic to
consider within language acquisition theories, and will be discussed later.
3.2. Current theories and research on auditory processing.
Autism and Asperger syndrome (AS) are subtypes of the larger spectrum of Autism
Spectrum Disorders. “…ASD is a spectrum of neurodevelopmental disorders characterized by
qualitative impairments in social interaction and communication, engagement in repetitive
behaviours and reliance on routine… The symptomatology of Autism and AS are similar,
however in contrast to autism, individuals with AS typically function at the higher end of the
spectrum” (O’Conner, 2012, p. 837). There is a significant amount of research done regarding
auditory processing in ASD, including studies focussing on speech perception, which will
provide a useful framework to compare and contrast with the linguistic theories previously
discussed.
Most of the research on auditory processing can be divided into two separate categories,
namely theories that focus on the social and communicational impairments and theories that
suggest more general sensory perception and processing issues. The relation of social
impairments to perceptual issues has been called into question, largely due to the evidence that
people with ASD show impaired performance on both social and non-social processing tasks.
Additionally, several studies did not include comparative experiments, making it more difficult
to conclude whether there would be a significant difference between performance on social and
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non-social tasks (O’Conner, 2012, p. 837). As such, theories regarding more general perception
and processing difficulties may be considered more useful. However, the social aspects of
communication and speech perception should not be dismissed entirely, especially considering
that a person is most likely to perceive natural speech within a social context, which could affect
that person’s perception to a certain extent.
Much of the research that focusses on the processing of sensory information has resulted
in the general theory that ASD individuals show enhanced perception and processing of local
information and details, while they also show a reduced performance of global information
processing, including integration of different sensory information (O’Conner, 2012, p. 838). A
well-documented example for auditory perception is pitch discrimination. Individuals diagnosed
with an ASD disorder have an increased ability for pitch discrimination from an early age. This
can however be compromised when the auditory stimuli becomes more complex (O’Conner,
2012, p. 838).
With regards to speech perception, some research done includes speech prosody.
O’Conner (2012) notes that many studies have focused on the prosody in the speech production
of ASD individuals, which is often suggested to sound artificial and inconsistent. In comparison,
less research has been done on how these individuals perceive prosody (p. 840). Studies that did
include prosody perception focussed on the social and emotional meaning of prosody in speech.
These studies found that individuals with ASD show a decreased ability to interpret the complex
voice expressions, and they had difficulty understanding the mental state of other individuals (p.
840). Additionally, a limited number of studies were done that focused on grammatical prosody,
specifically intonation and word stress. A few studies suggest that individuals with ASD can
have difficulty interpreting intonation, resulting in them judging questions as statements.
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However, the results were inconsistent across several studies, as well as between individuals,
suggesting that this topic may need further research (O’Conner, 2012, p. 840).
An important part of the research includes studies that focus on MRI and fMRI scans of
brain activity during auditory processing tasks. These studies show evidence of brain activity in
individuals with ASD that differs from typically-developed individuals. Specifically, ASD
individuals show a “stronger activation of right hemisphere frontal and/or temporal regions in
ASD to verbal information which may or may not be accompanied by weaker activation of left
hemisphere language regions. This pattern may be reflective of a processing difference and/or
compensatory strategy rather than an impairment per se” (O’Conner, 2012, p. 848). The idea of
alternative processing strategies is supported by the evidence that even when deviant brain
activity is observed, this is not always accompanied by impaired behaviour, suggesting that these
strategies may be effective to a certain degree (O’Conner, 2012, p. 848).
O’Conner (2012) points out that, although the auditory discrimination ability of
individuals with ASD is researched, the issue of relative loudness is not included in most studies
(p. 389). This suggests that though there is significant evidence for theories regarding acute
hearing and processing of details, there is less research that focusses on sensory sensitivity in
terms of both hyper- and hypo-sensitivity. This coincides with Pellicano’s (2013) criticism that
so far, few studies include the hyposensitivity also associated with ASD, while this may also
have significant implications for auditory processing, especially for the processing of complex
stimuli, such as speech.
When combined, most research supports the theory that ASD can be associated with
general perception and processing difficulties, including difficulties with complex auditory
information. These difficulties stem from a potential increase in detail-oriented perception
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combined with a reduced ability for more complex input, which may result in “impaired
performance on auditory tasks which require highlevel cognitive operations (i.e. attention,
comprehension) and … enhanced perception of low-level auditory stimuli” (O’Conner, 2012, p.
849). This includes a focus on bottom-op processing, and reduced top-down processing and
integration of different information into a more global context. The following sections will
discuss the topics regarding auditory perception within a linguistic framework to consider
potential implications for speech perception and language acquisition from a linguistic
perspective.
3.3. Speech Perception.
As mentioned previously, linguistic theories concerning speech perception suggest use of
both bottom-up and top-down processing (Ashcraft & Radvansky, 2010; Fromkin et al., 2011).
Considering the general perception and processing deviations associated with AS and ASD
(O’Conner, 2012), this may also relate to how these individuals process speech, specifically.
Increased bottom-up processing might indicate a stronger reliance on input in order to effectively
process speech. The alternate processing strategies may in that case also be a compensatory
strategy to facilitate the processing of the different acoustic characteristics of natural speech.
This strategy may be related to the reduced influence of higher-level functions and top-down
processing. This could mean that individuals with ASD rely more on the speech signal itself, and
make less use of contextual cues, such as semantic and pragmatic context. Overall, it may be the
case that auditory speech perception alone is less of an issue, but the reduced integration of
semantic and pragmatic cues may cause difficulties in resolving ambiguities, reducing effective
communication within specific contexts.
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Categorical perception as a strategy to facilitate speech processing may also be different
for ASD individuals. Perception for people with ASD is less reliant on top-down influence,
which would including reduces use of categories. One study conducted to research categorical
perception in individuals with ASD used visual stimuli as a basis. Participants were asked to
judge thinner and wider ellipses, and label them as either part of the thin or wide category. The
control group showed a discriminatory peek, referring to a longer reaction time when the
stimulus was close to the border between two categories. In comparison, the ASD group showed
no discrimination peek, suggesting they focus more on the stimulus as is, rather than depend on
perceptual categories during processing (Soulières, Mottron, Larochelle & Saumier, D., 2007).
This supports the theory that ASD individuals have an increased or more acute perception of
specific input, while relying less on top-down processing strategies such as categorization.
As previously mentioned, the use of categorical perception in experiments may not be as
reliable of a design as previously though, as many experimental set-ups would create a bias
towards the use of categorization as a strategy (Schouten et al, 2003). The experiment conducted
by Soulières et al. (2007), however, may still hold some value for theories regarding alternative
processing strategies used by AS individuals. The two groups were given the exact same
instructions, and were asked to categorize the stimuli according to specific categories, and yet the
AS group still showed a difference in performance, suggesting that they may rely on alternative
processing strategies even when the instructions would otherwise cause a bias for a
categorization strategy.
Another aspect of speech perception to consider within the framework of ASD perception
is the previously-mentioned integration of visual input. The McGurk effect has been used in an
experiment to investigate the audio-visual speech perception in adults with Asperger syndrome.
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Saalasti et al. (2012) used the previously mentioned set-up of combining auditory and visual
input. The auditory stimulus used was a meaningless vowel-consonant-vowel string, specifically
/aka/, /apa/ and /ata/. The auditory stimuli were combined with the visual image of a female face
articulating either /aka/ or /ata/. The main focus of the experiment was to combine the /apa/
auditory stimulus (Ap) with the visual /aka/ (Vk) and /ata/ (Vt), and to see how this affected the
reported perception of the subjects. The subjects were divided into two groups: adults diagnosed
with AS, and a control group of typically-developed adults. In addition to this set-up, the
experiment included an eye-gaze tracker in order to compare the gaze-movement and fixation of
the subjects when looking at the image of the female speaker. The authors initially predicted that
the group of adults with AS would perceive a weaker McGurk effect due to avoiding socially
relevant stimuli such as eye-contact, but also fixation on the mouth-region of the speaker,
resulting in perceiving less visual information. This did not appear to be the case. The eye-gaze
recordings showed no significant difference in eye-gaze behaviour between the two groups (p.
1611). Instead it appeared that the AS group perceived the McGurk effect differently from the
control group. Specifically when presented with the combination of Ap and Vk, while 95% of
the control group perceived the /apa/ as /aka/, the AS group showed a clear deviation, with 49%
perceiving /apa/ as /aka/, and 46% as /ata/. Additionally, the authors noted the significant
differences between individual performances of the subjects in the AS group, again suggesting
that this group is generally heterogeneous in nature. More specifically, the data did not show a
clear separation between perceptual differences, but a continuum of varying degrees of
perception. This would generally suggest that adults with AS do perceive audio-visual speech
input differently from typically-developed adults.
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A potential explanation for the different result of visual integration may again relate to
the alternative processing strategies associated with ASD (O’Conner, 2012). If they rely less on
the integration of visual input, perhaps this includes a limited facilitation of the visual input into
speech perception when that visual input is available. Instead, the visual input may cause some
disruption in the speech perception, especially considering how the results from Saalasti et al.
(2012) suggest that visual input affects the perception of AS individuals significantly different
from the control group, but also that the audio-visual perception varies much more between AS
individuals, as compared to the relatively homogenous control group.
3.4 Sensory sensitivity
Asperger (1944) included at least a few mentions of the sensory abnormalities
experienced by the children he observed. The observations included both hyper- and hyposensitivity, which suggested that these children might experience the world slightly differently,
more or less intense, but that this also varied individually and interpersonally. As previously
mentioned, Frith (1991) agrees that this was considered a primary observation and characteristic
of Asperger’s syndrome, although the actual significance and implications of the sensory deficit
were not easily integrated in the research and diagnostic framework until much later (p. 80). One
problem to consider is that although the behaviour of children and how it is affected by these
sensory fluctuations can be observed, it may be difficult to obtain accurate descriptions of what
these children actually experienced.
In a recent paper, Pellicano (2013) argues that sensory sensitivity is still not taken into
consideration in most studies. She also suggests that the issue may not be inherently sensory, but
related to the way in which the sensory input is processed and modulated, which results in
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deviant perception of the input. This may be due to the lack of integration of prior knowledge
and experience. Normally-developed individuals can use their prior knowledge, or ‘priors’, to
perceive and interpret sensory input more effectively. In contrast, “[t]he possibility that autistic
people perceive the world as it really is rather than as imbued by prior experiences may explain
the range and idiosyncrasy of their sensory sensitivities and their difficulties dealing with new
experiences“ (p. 143). Pellicano’s idea coincides with potentially reduced top-down processing
of ASD individuals. In the case of speech perception, these individuals may have linguistic
knowledge and experience, but may be unable to appropriately integrate this information during
speech perception, again resulting in limited use of semantic and pragmatic cues and context and
less effective communication.
A good attempt at a concrete account of the sensory sensitivity experienced by an autistic
child was reported by White and White (1987). Their son, Darren White, was diagnosed as
autistic with high intelligence, and the authors requested that he himself would try and describe
the sensory difficulties that he experienced. The account includes visual distortions of spaces and
objects, as well as severe and persistent difficulties with auditory disruptions and speech
perception. The authors considered that these perceptual difficulties are the root of many other
problems experienced by people with autism, and are caused by chemical imbalances in the
brain. This illustrates both the initial difficulties of pinpointing the cause and the larger
implications of this particular trait, specifically how it may affect people’s everyday functioning.
Additional findings were reported by Reynolds, Lovaas and Newsom (1974), who
exposed children with ASD to complex auditory stimuli. While typically developing children
could use different elements of the stimuli to recognize a specific signal, children with ASD do
not show this ability. Instead, they clearly focus on one element of complex stimuli and use that
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to identify it. If that particular element is absent, the child can no longer identify the stimulus.
This overselectivity would suggest a difficulty in integrating a multitude of elements, and an
almost strategic preference for focussing on single elements. Overselectivity may also have some
social and behavioural implications. If the experimental results represent infants’ natural
preference for overly selective hearing, this may explain part of the limited attention they display
towards speech. Natural speech varies greatly across speakers, and is often accompanied by other
background noise, which can potentially obscure immediate recognition.
3.5 Language Delay
As mentioned previously, one of the most prominent characteristics of autism and
Asperger syndrome with regards to language development is the apparent language delay during
early childhood. While some children with more severe cases of autism never develop their
verbal language skills, in other cases the initial delay may be completely resolved around the age
of 5 (Attwood, 1998; DuCharme & Gullotta, 2013). It has even been suggested that the language
delay can be used to differentiate between autism and Asperger Syndrome, specifically because
AS is commonly associated with the lack of a clinically significant language delay (Bennett et
al., 2008, p. 616). Once the potential delay is resolved, some children may be especially
talkative, and yet their social and communicative skills may be lacking. This could suggest a
very close and complicated connection between language acquisition and social development.
However, these two aspects may not be entirely mutually dependent, considering a child with AS
can still fully acquire the phonetic and syntactic system of his or her native language, and yet still
have severe social limitations.
22
Several theories have suggested different causes for the language delay in children with
autism and AS. One of the most prominent theories is based on the close connection between
language development and social behaviour. Dawson et al. (2004) consider several forms of
social attention, namely social orientation, attention to distress and especially joint attention:
“Joint attention refers to the ability to coordinate attention between interactive social partners
with respect to objects or events in order to share an awareness of the objects or events” (p. 237).
Within conversations, joint attention allows multiple participants to focus their attention on the
same person or object, follow each other’s attention, most commonly by eye-gaze, as well as ask
for the others’ attention. In many cases, as Dawson et al. report, there is significant evidence for
the correlation between children’s social attention skills and their language abilities (p. 237).
This theory, based on social attention and interaction, may have its limitations, considering many
children eventually do complete their language development, while still showing socially deviant
behaviour.
There is some neurological evidence that also suggest a link between the social and
linguistic processing of speech, and what implications this connection has for children with
autism and ASD. Kuhl, Coffey-Corina, Dawson and Padden (2005) recorded Event-Related
Potentials (ERP) to combine and compare behavioural observations with brain activity. This
study was carried out with preschool children to explicitly research the delicate connection
between social behaviour and language perception. The experiment was largely based on the,
then re-established, observation that children with autism show a distinct lack of interest for
human speech, and when faced with a choice appear to prefer a non-speech sound signal. Next to
an auditory preference test between child-directed speech and a non-speech analogue, the
experimental trials included an ERP test that measured the children’s brain activity when
23
presented with an auditory stimulus. The stimulus consisted mostly of /wa/, but included a
deviant stimulus of /ba/ 15% of the time. When perceived, this deviant should result in a strong
ERP signal. While the control group did produce the expected ERP signal, the children in the
ASD group showed no strong activity. By assigning children with ASD into subgroups, it
became apparent that the group’s average was not representative of all children’s results, and that
one subgroup showed activity more closely resembling the control group than the second
subgroup. This correlated with the auditory-preference test results where the first ASD subgroup
did show some preference to the speech signal, while the second subgroup preferred the nonspeech signal. Kuhl et al. consider the results strong evidence for the link between social and
linguistic processing, and suggest that the socially deviant behaviour of children with ASD may
play a role in their language acquisition.
The results of this study may have some limitations, as Kuhl et al. (2005) rely on the
suggested role of child-directed speech in language acquisition. Child-directed speech is a
simplified way of speaking, often used by parents to speak to their infants, also referred to as
motherese. The role of child-directed speech in language acquisition is still a point of discussion.
Kuhl et al. suggest that it is beneficial to language development, as “... infant-directed speech
contains particularly good phonetic exemplars – sounds that are clearer, longer, and more distinct
from one another – when compared to adult-directed speech” (p. F2) However, other authors
argue that it is by no means crucial (O’Grady, 1997, p. 249-251). Children may have a social
interest in being spoken to, but this may not necessarily significantly affect their actual language
development to the point where children not exposed to child-directed speech would not properly
develop their language skills. Some evidence of this comes from countries and cultures where
children are rarely spoken to in a direct manner, either in adult speech or child-directed speech,
24
and will only be spoken to once they manage to produce multi-word utterances (Harley, 2010, p.
61). As such, child-directed speech may be more of a social aspect of a child’s development,
rather than an inherent part of language and language learning. The use of motherese may be
considered a part of the social development of a child, and the lack of interest for motherese may
be an important part of the deviant social behaviours of children with autism and AS. However,
considering the likely limited role of motherese in language acquisition, perhaps it should not be
considered an intrinsic element of the language delay in children with autism and AS.
As previously discussed, however, exposure to spoken language, motherese or otherwise,
is most definitely an important element of a child’s language development. Even if not spoken to
directly, a child will still benefit from language spoken in its environment (O’Grady, 1997, p.
251-252; Harley, 2010). Reduced interest for or attention to speech may result in a reduced
amount of input to facilitate language acquisition, which could play a role in the observed
language delay.
Next to research centred on the social aspects of language acquisition, studies have
focussed on children’s phonetic acquisition. Bartolucci, Pierce, Streiner and Tolkin Eppel (1976)
compared the phonetic acquisition of children with autism to that of mentally handicapped
children. Both groups show a similar delay in phonetic acquisition, though neither showed any
deviant order in which phonemes were acquired. Based on the specific errors that autistic
children made, the authors suggested that some part of the language delay in these children may
be due to them using different strategies to acquire their phonetic knowledge. As their research
only weakly supported this idea, Bartolucci et al. strongly suggested continued research on this
particular topic.
25
The evidence provided by Bartolucci et al. (1976) regarding the phonetic acquisition of
children with autism also suggests that, despite the apparent social and behavioural issues during
infancy, linguistic knowledge can still be acquired. Although the acquisition process is delayed,
it does not result in significantly deviant phonetic or syntactic knowledge to suggest a specific
language impairment. The enhanced processing capability for details, combined with less
integration of more global information may require the use of alternative acquisition strategies to
compensate. An infant may be more perceptive of specific characteristics of speech, but may
have difficulty to process the complex speech into useful information. Additionally, Pellicano
(2013) suggestion of limited integration of previously gained knowledge and experience may
play a role in how effective children with ASD can bootstrap new information onto previously
gained knowledge. Most importantly, however, Bartolucci et al. (1976) findings regarding the
stages of language acquisition in children with autism may suggest that although individuals with
ASD have to rely on different processing strategies during auditory perception and language
acquisition, these strategies still follow the general pattern of language acquisition according to
Universal Grammar. This could explain why children with ASD may still fully develop their
phonetic and syntactic acquisition. If this is the case, the connections between social behaviour
and language acquisition may be more related to the semantic and pragmatic aspects of language,
and potentially less with the phonetic and syntactic elements.
A key element that connects language acquisition and social learning during development
is the role of mirror neurons. As previously discussed, mirror neurons facilitate skill learning
based on observing and imitating other people’s behaviour and actions, specifically within a
social context. Within ASD, there is an indication of a deficit of mirror neurons, which may be
the cause of some deviant social behaviour (Purves, 2013, p. 382). Mirror neurons may be what
26
connect the acquisition of linguistic knowledge with acquisition the skills necessary to use this
linguistic knowledge in a social context. A deficit of mirror neurons may thus prevent infants
with ASD to effectively develop the skills and experience necessary to use their linguistic
knowledge effectively, resulting in the developmental delay. The social deficits associated with
ASD may be valuable for researching the role of social behaviour and context for language
acquisition and development. Considering the amount research available regarding social deficits
in Asperger syndrome and ASD, this particular topic is well beyond the scope of this paper.
4. Conclusion.
To summarize, this paper set out to combine the linguistic framework of speech
perception with theories describing the perception and processing difficulties associated with
Autism Spectrum Disorders. This was done in order to illustrate the potential difficulties that
people with ASD may experience during the processing of natural speech, but also how their
processing strategies are different from strategies used by typically-developed individuals.
Theories regarding language acquisition were also discussed, to consider the potential effects of
auditory perception issues on infants’ language development.
Typically-developed adults combine bottom-up and top-down processing strategies to
process natural speech. They can use both the incoming speech signal and their own semantic
and syntactic knowledge to process the signal in order to derive its meaning fast and effectively.
To compare, individuals with ASD have been reported to different processing strategies,
including increased bottom-up processing and a decreased influence of top-down processes,
which may also influence how effectively they process speech. Categorical perception usually
allows people to label specific stimuli as being part of a distinct category. In comparison,
27
individuals with ASD may be faster with processing specific stimuli without relying on distinct
categories (Soulières et al., 2007). Similarly, typically-developed adults can make use of visual
input to facilitate effective speech processing, while adults with ASD may perceive the combined
audio-visual input significantly different (Saalasti et al., 2012).
One particular characteristic associated with AS and ASD in sensory sensitivity.
Pellicano (2013) recently suggested that sensory sensitivity is not strictly a matter of acute
sensory perception and enhanced bottom-up processing, but instead the cause of reduced
integration of prior knowledge and experience to interpret incoming sensory signals. This
supports the general theory of reduced top-down processing in individuals with ASD, which
includes the potentially limited use of semantic and pragmatic knowledge during speech
perception.
ASD is associated with delayed language development. Specifically Asperger Syndrome
poses an interesting challenge for language acquisition theories, as it is characterised by delayed,
but often complete language development, with persistent social and behavioural difficulties.
The language development of children with AS may be delayed, but the stages of acquisition are
not significantly different from typically-developing children (Bartolucci et al., 1976). This
suggests that the alternative processing strategies observed in ASD still rely on UG to complete
children’s phonetic and syntactic acquisition. Instead, the social deficits that also characterise
ASD may affect the acquisition of knowledge and skills to use language effectively within a
social context. The social deficits in ASD may be useful for linguistic research regarding the
importance of social interaction and context during a child’s language acquisition.
28
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