Humour Comprehension and Use of Mental State Language in Williams Syndrome and Down Syndrome-Juniper Publishers
Global Journal of Intellectual & Developmental Disabilities (GJIDD)
Good humor comprehension and mental state language
use is reported to be associated with good theory of mind (ToM)
capabilities. There is limited research on humor comprehension in
Williams Syndrome (WS) and Down Syndrome (DS), but related research in
non-literal language and humour comprehension in people with
intellectual disabilities suggest humor comprehension may be impaired in
these populations. Furthermore, there is mixed evidence for ToM in WS
and DS and limited research exists on the use of mental state language
in either WS or DS. So far, the literature suggests that people with WS
have are good at inferring emotions, however both WS and DS individuals
have difficulties with producing cognitive language (e.g., thinks,
believes). The current study sought to examine humour comprehension and
use of mental state language in WS and DS relative to one another and
relative to neuro typical controls, as well as the relationship between
humour comprehension and mental state language use. Participants (30 WS;
18 DS; 27 CA; 30 MA controls-17 MA matched to WS; 13 MA matched to DS)
were shown 23 cartoon jokes and were asked to explain what was funny.
The results revealed poor humour comprehension in WS and DS relative to
CA matched controls, but WS and DS individuals showed a comparable
performance to each other and to MA matched controls. Furthermore, the
groups only differed on the use of physical emotion words (e.g.,
laughing, crying, screaming) and cognition words (e.g. thinks). WS used
fewer physical emotion words than DS and CA matched controls, but their
frequency of use was equal to MA matched controls. The DS group did not
differ relative to either CA or MA matched controls. Regarding use of
cognition words, both WS and DS groups used fewer than CA controls, but
performed similarly to each other and to their relative MA matched
controls. Lastly, humour comprehension was not associated with humour
comprehension for WS or DS individuals, only CA and DS MA matched
controls. The study provides unique findings and evidence for humour
comprehension in WS and DS that is similar to MA levels, but below CA
levels. Results highlight the importance of intellectual ability in
processing humour. Social implications and avenues for future research
are discussed.
Humour is an important aspect of daily human life
across the world. Laughter is a pattern of vocalizations in response to a
humorous stimulus, and is one of the first social vocalizations
produced by an infant, after crying McGhee [1].
We encounter humour in many different forms in our day to day lives,
including interpersonal joking and banter, comedy films and TV shows and
cartoons in newspapers, books, or on the internet Martin [2]. Humour is considered an essential phenomenon for successful social interaction Yip & Martin [3], as it aids in communicating ideas, feelings and opinions Nezlek & Derks [4].
To produce humour, one needs to be able to process
information from the environment or from memory and manipulate ideas,
words and actions to generate a funny action or comment. Understanding
humour involves processing the meaning of the humorous stimuli that has
been heard or viewed, and appraising it as humorous and non-serious
Martin [2].
Although there are many theories of humour
comprehension, one of the most widely accepted is the
incongruity-resolution theory Suls [5].The
theory states that in order to understand humour, one first needs to
detect an incongruity, which is usually an outcome that does not conform
to the prediction the recipient made. Then the next step is to resolve
the incongruity by finding a rule that makes the ending follow from the
rest of the joke. Accordingly, understanding humour is viewed as a
problem solving task.
Keywords: Theory of mind; Emotion Development of Humour
HumourChildren and adults laugh at objects and events
that do not conform to their existing schemas or perception of the
world. That is, they laugh at incongruity. Schemas are constantly
building as children develop, thus the things that may have been funny
at an earlier age often become non-humorous at a later age, and other
things that may not have been funny at a younger age, are humorous when
older due to more sophisticated schemas allowing newer incongruities to
be more comprehensible Martin [2].
McGhee [1]
proposed a four-stage model of humour development. In stage 1 (18-24
months) children deliberately play with objects in ways that are
incongruous to their normal functional use. For example, using a bucket
as hat. In stage 2 (24–36 months), children alter the relationship
between verbal labels and objects, that is, incongruous labelling of
objects and events such as inventing nonsense words and using wrong
names for objects or body parts. Stage 3, conceptual incongruity (3-7
years) involves children deliberately altering one or more properties or
attributes of events, objects or words instead of just mislabeling it.
An example of jokes that children may find funny at this stage is a
picture of a cat with two heads saying moo instead of meow. In stage 4,
multiple meanings (7-11 years), children develop awareness of ambiguity
and words with multiple meanings and that is regarded as the onset of
adult humour
Humour and Theory of Mind
Theory of Mind (ToM) is the ability to recognize and
attribute mental states such as beliefs, intentions, knowledge, desires
and emotions, to self and others in order to predict behavior and
outcome Premack & Woodruff [6].
ToM starts developing from infancy and early childhood (ages 2-3
years), when children develop skills such as joint attention,
recognizing and displaying emotions, imitating expressions, pretending
to be someone else (e.g. pretend play), recognizing that different
people have different desires and that their actions are determined by
these Westby & Robinson [7].
Between the age of 4 and 5 years, children are able to predict what
others are thinking and, in turn, predict other people's actions based
on their beliefs and thoughts (first order ToM) Westby & Robinson [7].
By ages 6-8 years, children can predict what someone is thinking (or
believes) about what someone else is thinking (or believes) (second
order ToM) Westby & Robinson [7].
Around 8-10 years, children develop higher order ToM, that is, they are
able to understand, detect and use deception, lies and figurative
language Westby & Robinson [7].
Studies investigating humour comprehension in neuro
developmental populations that have reported ToM deficits, such as
autism spectrum disorder or schizophrenia, have provided evidence that
ToM deficits impact on humour comprehension abilities Emerich et al. [8] and Wu et al. [9].
Studies have shown that both ToM and humour comprehension are related
to activation in the prefrontal cortex, which is known to mediate
abstraction, reasoning and problem solving (executive function)
Aboulafia-Brakha et a. [10], Samson et al. [11].
A recent study by Wu et al. [9]
investigated humour comprehension and appreciation of
incongruity-resolution jokes and nonsense jokes in high school students
with ASD. The results showed that the individuals with ASD understood
fewer of the incongruity-resolution jokes compared to typical age, sex
and intelligence matched controls and they also found nonsense jokes
funnier than incongruity resolution jokes compared to typically
developing peers. The authors suggest that the lack of ToM may interfere
with understanding the punch line. However, the authors measured
comprehension of jokes by asking participants to rate how funny each
joke was on a 9-point scale. This is problematic, because how funny a
joke seems is subjective and depends on one's sense of humour. That is,
even if the individual comprehends the joke, they may rate it as not
being funny, because they did not find it humorous, thus the
comprehension measure may have poor construct validity. Furthermore, the
study utilized purposive sampling, that is, ASD participants were
selected by the researcher based on notable impairments in communication
and social interaction, as well as an overall IQ greater than 70. This
may limit the generalisibity of the results, especially because ASD is a
very heterogeneous disorder Lenroot et al. [12].
Another study examined humour in ASD Emerich et al. [8]
asked participants to select the correct ending to a selection of
cartoon jokes and found that clinical groups made more errors in
selecting the correct ending compared to typically developing controls.
However, the study had a small sample which consisted of only eight ASD
participants and eight typically developing children, thus
generalizability of results to the clinical population may be low.
Additionally, although the control subjects were age matched and sex
matched to the clinical subjects, IQ was not controlled, which may be a
confounding variable to humour comprehension Greengross & Miller [13].
Schizophrenia is also a disorder with known deficits in ToM abilities Brüne [14]. Varga et al. [15]
investigated verbal humour comprehension in adults with schizophrenia.
They presented all participants with story form verbal jokes and
semantic scenarios to measure literal interpretation abilities. They
also measured ToM abilities using first order (knowledge about
characters' beliefs) and second order ToM tasks(what one character
thinks about another character's thoughts). The results showed that
individuals with schizophrenia performed significantly lower on the
humour task compared to healthy controls, which involved participants
rating a humorous scenario as funny and justifying their response.
Individuals with schizophrenia in their study also performed lower on
second order ToM tasks compared to healthy controls, but no group
differences were obtained on first order ToM tasks. Varga et al. [15] did not find any significant associations of comprehension of verbal humour with ToM abilities.
Similarly, Marjoram et al. [16]
conducted a study investigating appreciation of picture jokes in
schizophrenia patients. The participants were presented with63 single
image cartoons of which 31 were ToM cartoons, that is, they required
attribution of ignorance, false beliefs or deception of one character
and mental state analysis to understand the jokes. Marjoram et al. also
used 32 physical cartoon jokes that were behaviorally based and did not
require ToM for correct interpretation, for example a man pushing swings
like a pendulum. The results showed that individuals with schizophrenia
had significantly lower scores for both joke types compared to
controls, but the schizophrenia patients also performed significantly
lower on ToM jokes compared to physical jokes relative to healthy
controls.
Studies on people with right hemisphere brain damage
also suggest that the humour comprehension difficulties they exhibit are
partly due to ToM deficits, which have been found following right
hemisphere brain damage Bihrle et al. [17], Winneret al. [18].
Humour in williams syndrome
William's syndrome (WS) is a rare neuro developmental
disorder involving a deletion on chromosome 7, which, in turn, affects
26 to 28 genes Schubert [19].
It is characterized by cardiac defects, atypical facial features and
mild to moderated intellectual disability (IQ usually ranges from 60-70,
on average). Individuals with WS tend to have good receptive
vocabularies, but poor performance on measures of nonverbal ability,
such as drawing, visuospatial, planning and number processing Bellugi et
al. [20], Brock [21]. Individuals with WS are typically extremely friendly and outgoing Doyle et al. [22], however, even with excessive desire for social contact, they have difficulty maintaining friendships Laws & Bishop [23].
Individuals with WS often have difficulties with pragmatics, such as
turn taking during conversations, conversational coherence and
appreciation of conversational context Laws & Bishop [23].
No studies to date have examined comprehension of
picture jokes in WS. There are, however, studies that have looked into
non-literal language comprehension in this population. Verbal humour can
be considered a non-literal form of language, that is, its
understanding requires pragmatic competence, such as drawing inferences
about the speaker's utterance Varga et al. [15]. Sullivan et al. [24]
investigated whether adolescents with WS, Prader-Willi syndrome and
individuals' with non-specific intellectual deficits were able to
distinguish between lies and jokes. Prader-Willi Syndrome is another
neuro developmental disorder associated with intellectual disability
Cassidy et al. [25]. Sullivan et al. [24]
presented individuals with short stories that ended with either a lie
or a joke and asked them to classify the story as a lie or a joke and
give a reason for their response. The results indicated no differences
between the groups, with all participants finding it difficult to
identify ironic jokes and classified them as lies, as they did not
correspond to reality. These errors are similar to errors made by
younger typically developing children. The study did not employ a
healthy control group and it is, therefore, difficult to judge the
degree of impairment relative to typical humour performance by age
matched typically developing children.
Moreover, a study by Godbee & Porter [26]
explored comprehension ofsarcasm, metaphor and simile in WS. The
results showed that the WS children were poorer at comprehending
non-literal language compared to chronologically age matched typically
developing children, but performance of WS was not significantly
different to mental age matched control children.
Humour in Down Syndrome (DS)
Down Syndrome (DS) is a genetically based disorder
caused by the presence of an extra chromosome 21. Apart from the
physical characteristics, it is most commonly associated with varying
degrees of intellectual disability and delayed language ability Abbeduto
et al. [27]. There's been limited research on humour comprehension in Reddy V et al. [28]
conducted a cross sectional study on humour and laughter of DS and ASD
children matched on nonverbal IQ. They asked parents to video record or
report/recall instances of humorous interactions (eliciting laughter,
clowning, teasing) of their children. Results indicated that DS children
tended to laugh more at or with other's laughter, had more instances of
clowning (making others laugh) and engaged in teasing more than ASD
children. St James and Tager- Flusberg [29]
conducted a similar observational study in age and language matched DS
and ASD groups, in which they observed and recorded incidences of
laughter during mother-child play interactions over the course of one
year Results indicated that the DS group overall had more incidences of
laughter than the ASD group. However, it is difficult to judge if humour
in DS is impaired relative to typically developing children from these
results and instances of laughter do not necessarily reflect humour
comprehension.
Evidence from other intellectual disorders
Several studies on humour have been conducted with children with non-specific intellectual disabilities. Bruno et al. [30]
conducted a study on verbal humour comparing children with learning
(academic) disabilities, children with intellectual disabilities and
typically developing children. Children were asked to complete the jokes
by selecting the correct joke ending. They were then asked to also
explain the joke. The authors had 3 categories of jokes corresponding to
McGhee's proposed stages of humour development. The three categories
were phonological (humour due to changes in sounds, thus creating
multiple meanings), lexical humour (same word used in different
meanings) and incongruity based humour (based on illogical resolution).
They found that typically developing children scored higher than the
other two groups overall and that children with an intellectual
disability found it harder to explain phonological humour than lexical
or cognitive humour.
Similarly, Degabriele & Walsh [31]
conducted a study exploring humour comprehension in children with mild
to moderate intellectual disabilities using an appreciation task, as
well as a comprehension task. In the appreciation task children watched
episodes of SpongeBob Square pants and assigned ratings of funniness
after each scene. They were also presented with 12 question and answer
type jokes/riddles, with or without visual aids (pictures, gestures,
acting), and then given a multiple choice question about why the joke
was funny.
Results showed that the participants rated physical
jokes (funny action) and visual jokes (something looks funny) as the
funniest compared to the verbal jokes (funny spoken comment or joke).
They also found that when a joke is told with supporting gestures or
pictures, comprehension of the joke is higher in children with
intellectual disabilities compared to when the jokes are not supported.
It is important to note that the study had a very small sample size of
nine, which limits the generalizability and did not include a typically
developing control group.
Theory of mind and williams syndrome
Karmiloff Smith et al. [32] conducted one of the first studies on ToM in WS. Karmiloff-Smith et al. [32]
gave participants ToM tasks measuring first and second order abilities.
The authors found that individuals with WS performed similar to
typically developing children and performance was significantly better
than individuals with ASD. However, the authors only used ToM measures
that were language based, which is a potential confound since verbal
abilities in WS are a relative strength and could have aided their
performance on the ToM measures. Another study assessed ToM in WS adults
using a visual task in which participants were presented with
photographs of eyes and asked to name the mental state Tager-Flusberg et
al. [33].
Results showed that individuals with WS performed better than those
with Prader-Willi Syndrome, but that only 50% of the WS participants
performed as well as CA matched typical adults. This suggests that there
are some potential ToM difficulties in WS. However, the authors did not
match for IQ, which was significantly different in WS and Prader-Willi
participants compared to typical adults.
Furthermore, Porter, Coltheart & Langdon [34]
conducted a ToM investigation in WS individuals using a nonverbal
picture sequencing task and found that individuals with WS performed
significantly lower than CA matched typically developing participants on
false belief tasks, but performance was similar on other aspects of ToM
(intention, pretence, social script knowledge, cause and effect
reasoning).
Santos & Deruelle [35]
conducted a study examining attribution of intentions in WS compared to
typically developing children via a visual measure, as well as a verbal
measure(designed to be equivalent) of attributing intentions. They
found that there was no difference across the groups in task performance
when material was presented verbally, however, the WS individuals
tended to make more errors in selecting the correct response for the
visual task compared to the controls. Furthermore, the WS participants
made more errors in attributing intentions than controls in the visual
condition. The two studies mentioned above both individually matched WS
participants to MA matched controls.
Tager-Flusberg & Sullivan [36]
proposed that there are two components of ToM and that WS individuals
have relatively more impairments in one of these components. The two
components outlined are the social-cognitive component and a social-
perceptual component. The social-cognitive component refers to the
traditional ToM definition. That is, being able to represent mental
states (false beliefs, intentions), typically accessed via traditional
false belief ToM tasks (e.g. Sally-Anne). The social perceptual
component, on the other hand, is the ability to distinguish between
people and objects and also make implicit judgments about mental states
through facial expressions and body language. Tager-Flusberg and
Sullivan suggest that WS individuals have relatively less difficulty
with social-perceptual ToM, but more difficulties with social-cognitive
ToM Tager- Flusberg & Sullivan [36].
Theory of mind and Down Syndrome
ToM research in DS is limited, but generally suggests
that ToM capabilities are commensurate with IQ-levels in DS.
Baron–Cohen et al. [37],
for example, were one of the first to investigate ToM in DS and
compared performance on false belief tasks (Sally-Anne task) in ASD, DS
and typically developing controls. The results indicated that DS and
typically developing children performed equally well on the false belief
tasks. However, the authors did not match participants on MA or CA,
both of which could potentially confound ToM results due to the
different developmental trajectories Abbeduto et al. [38]. Some studies do not suggest intact ToM in DS, for example, Giaouri et al. [39]
compared ToM performance in DS individuals, children with Intellectual
disabilities (IQ ranged from 55-70)and typically developing controls,
with all participants being matched on overall MA, but not CA
(intellectual disabilities group had higher CA). The results signified
the DS group performed significantly lower on the false belief tasks
than typically developing and intellectual disability groups, implying
that ToM is not intact in DS of relevance in this context is that most
of the literature on ToM in DS assesses traditional false belief tasks.
Mental state language in WS and DS
Mental state language is the term given to the
linguistic expression of a person's thoughts, emotions and beliefs and
some suggest is an indicator of ToM abilities Longobardi et al. [40].
Indeed, Mental State language use and ToM abilities are reported to be
associated in typically developing children Dunn et al. [41].
There is limited research on mental state language use in WS and DS populations. Tager-Flusberg & Sullivan [36]
explored the ability to explain an action through the use of mental
states in children with WS and Prader-Willi Syndrome. Tager-Flusberg and
Sullivan presented stories to children who were asked to explain the
actions of the main character e.g. "why did Sally run when the dog gets
up? The results indicated that there was no significant difference
between WS and Prader-Willi Syndrome in the number of mental state
explanations, but overall both groups used more desire words (e.g.,
want) relative to emotion (e.g., sad, angry) and cognition words (e.g.,
know, forgot).
A few studies have explored mental state langue use in WS and/or DS populations using a narrative task Jones et al. [42], Van Herwegen et al. [43]. Van Herwegen et al. [43],
for example, examined the use of emotions in narratives in WS compared
to CA matched typically developing children. Results revealed that both
WS and CA controls produced similar proportions of emotion words, but WS
produced more emotion words related to sadness than CA controls. A
similar study employing narratives found contradictory evidence Jones et
al. [42], Reilly et al. [44]. The Jones et al. [42]
study revealed typically developing controls used more cognitive
inferences (motivation, causality and mental states) than WS group, but
WS used more social engagement language (character speech, sound
effects) than age matched normal controls.
Reilly et al. [44]
examined the use of mental state language in WS, DS and MA matched
controls. Reilly et al. coded each participant's narrative in response
to a picture for affective enhancers (affective states, character
speech, sound effects) and social cognitive enhancers (mental states,
inferences, causality and negation). Results indicated that WS used
significantly more affective language relative to DS and MA matched
controls. WS group also used more cognitive language than DS, but did
not differ from MA controls. Furthermore, DS group used less of each
category relative to MA controls. There are no studies examining the
relationship between mental state language use and humour comprehension
in WS and DS, perhaps surprising given both mental state language use
and humour comprehension are reported to be associated with ToM Varga et
al. [15], Marjoram et al. [16], Bihrle et al. [17], Dunn et al. [41].
Aims
The first aim of the study was to examine humour
comprehension (understanding of picture jokes) in WS and DS both
relative to one another and relative to typically developing CA and MA
matched controls. The second aim was to compare use of mental state
language across the four groups. The final aim was to investigate how
use of mental state language related to the understanding of humour.
Hypotheses
It was hypothesized that once IQ was controlled WS
and DS groups would display similar levels of humour understanding and
significantly lower humour comprehension scores than the CA matched
control group. No significant difference in performance was expected
between WS, DS and their MA matched controls.
Regarding the use of mental state language, it was
expected that: WS participants would not differ significantly from CA
matched or MA matched controls in their use of mental state language; WS
would produce moremental state language compared to DS participants; DS
participants would provide less mental state language compared to CA
and MA matched controls. Thirdly, it was predicted that a higher score
on humour comprehension would be associated with higher usage of mental
state words in the explanation.
Method
Participants
5.1.1. Williams Syndrome: Twenty-seven English
speaking Williams Syndrome (WS) individuals (16 males) aged 5-31 years
(M=14.89, SD=6.96) were recruited from Williams Syndrome Australia
Limited to participate in the study All participants had a formal
clinical diagnosis of WS confirmed genetically using a FISH
(Fluorescence in situ hybridization) test to look for the elastin gene
deletion. Mental age (MA) ranged from 3.58–9.33 years (M=5.57, SD=1.35)
as assessed using the Woodcock Johnson psycho-educational Battery,
Revised (WJ-R).
5.1.2. Down Syndrome: Sixteen English speaking
individuals with Down Syndrome (10 males) aged 6 to 31 years (M=14.46,
SD=6.36) were recruited through the NSW Departments of Community
Services and Ageing, Disability and Home Care and the Down Syndrome
Association NSW. Mental age was assessed via the WJ-R, ranged from 4-
6.16 years (M=4.87, SD=0.75).
Neuro typical Controls
All controls were screened for intellectual disability Woodcock Johnson [45], neurological and psychological impairment, learning difficulties and developmental disability.
Chronological age matched controls
Participants were 27 (13 females) English speaking
neuro typical adults. Thirteen participants were first year psychology
students recruited from Macquarie University and 14 were children
recruited from Neuronauts, a children's science club at Macquarie
University. Their chronological age ranged from 5 to 31 years and mean
age was 15.15 (SD=6.81).
Mental age matched controls
Thirty MA control subjects were recruited through
Neuronauts. Seventeen (9 females) participants were individually matched
to WS participants on mentally age using the WJ-R, which formed the MA
comparison group for WS (MAWS). The mean MA of this group was 6.11
(SD=1.46), ranging from 3.67 to 9.5. An additional 13(5 males)
participants were individually matched to 16 DS participants on MA to
form the MA control group for DS (MADS). MA of the latter group ranged
from 4 to 6, with a mean MA of 5.17(SD=0.61).
Materials and Apparatus
Picture jokes
A total of 23 humorous cartoons, selected from
children's picture books, were used to measure humour comprehension
Durkin & Ferguson [46], Factor & Marshall [47,48], Factor & Viska [49,50], Rosenbloom & Hoffman [51].
The jokes also measured ToM indirectly, as the jokes often required the
individual to be able infer beliefs, emotions or desires of the
characters in the cartoons and thus could be explained using mental
state terms, similar to those used in Marjoram et al. [16] and Bihrle et al. [17]. For example, in Figure 1,
to understand the first joke, individuals would need to know that the
bird hunter thinks it's a real bird, a false belief that the explorer
character holds. To understand the second, participants could interpret
the joke by inferring that the character is happy and un ware of the dog
licking her because she thinks it's the boy kissing her. The joke
responses were scored on a scale of 0 to 2. A score of 0 reflected an
irrelevant or incorrect understanding of the joke, a score of 1 was
awarded if the response was partially correct and was identifying parts
of the humorous aspects and a score of 2 for a response if it was
comprehensively identifying the core humorous aspects. Each joke had
specific scoring criteria (available from the third author on request) Figure 1.
Woodcock-Johnson Psycho-educational Battery-Revised Woodcock & Mather [52] the Woodcock Johnson psycho- educational battery revised (WJ-R) Woodcock & Johnson [52],
a test of cognitive ability, is a revised version of the test first
published in 1977. It is based on the Horn-Catell theory of
intelligence. The standard battery of tests 1-7 (memory for names,
memory for sentences, visual matching, incomplete words, visual closure,
and picture vocabulary and analysis synthesis) was administered to each
participant to measure their cognitive ability and calculate MA. The
subtests measured each of the different abilities that compromise
intellectual ability outlined by Horn-Catell theory including: long term
retrieval; short term memory; processing speed; auditory processing;
visual processing; comprehension and fluid reasoning. The WJ-R has sound
psychometric properties, including reliability and validity Woodcock
& Mather [52].
Procedure
The cartoon jokes were presented to the participants
in a randomised order and participants were asked to explain what was
funny/what the joke was for each. Participants were prompted if they
gave no or vague response or said "I don't know” The responses of each
participant were recorded verbatim. All participants were then
administered the WJ-Rto calculate their MA.
Analysis/scoring
All the jokes were scored by two independent raters
and the correlation between the sores yielded 95% agreement. The
remaining 5% with disagreement were scored by a third blind rater to get
a final joke score. The final score given to each participant per joke
was the majority score among the 3 raters, and if there was no majority
agreement, the three scores were averaged (three joke responses overall
had no majority agreement). Total joke score (sum of score on all 2 3
jokes) was calculated for each participant and was used to measure
humour comprehension.
Use of mental state language was analyzed by counting
the number of mental state words or phrases the participants used in
their response. Mental state words were categorized as: emotion words
(e.g., sad); physical emotion words (e.g., laughing, crying); desires
(e.g., wants); cognition words (e.g., thinks); pain (e.g., hurt) and
character speech (Full list of words under each category is available
from the third author on request).These categories were similar to those
employed in Tager-Flusberg & Sullivan [36] and Reilly et al. [44],
encapsulating both affective and cognitive language. The proportion of
each category words to total number of words used (for all 23 jokes) was
calculated before prompt and after prompt.
Results
Demographics
Note: CA is in years and MA was measured via the WJ-R
is also in years; MAWS= MA matched controls to WS; MADS= MA matched
controls
Refer to Table 1
for means and standard deviations of CA and MA for each group. WS, DS
and CA matched controls did not differ significantly on chronological
age (F (2,67)=.05, p=.95). There was no significant difference in mental
age between the WS and the corresponding MA matched control group
(MAWS) (t(45)=-1.04, p=.304) or between the DS and their MA matched
control group (MADS) (t(29)=-1.47, p=.154) Table 1.
Humour Comprehension
7.2.1. WS vs DS vs CA controls: Correlation analysis
revealed that MA was significantly related to joke scores both before
prompt (r=.63, p<0.001) and after prompt (r=.66, p<0.001) (Prompts
were given if participants did not give an adequate response to the
jokes). Therefore, MA was entered as a covariate in all following
analysis on humour comprehension.
Repeated measures univariate analysis of covariance
(ANCOVA) with group as a between subjects' factor (three levels: NCA, WS
and DS), prompt as a within subjects' factor (two levels: before prompt
and after prompt) and mental age as a covariate was conducted to test
for any differences between the groups on the joke task. The results
revealed a significant main effect for group (F (2,66) =16.86,
p<0.001). However, there was no significant difference overall in
scores before or after prompt (F(1,66)=.52, p=473) and no significant
prompt by group interaction (F (2, 66) =2.93, p=0.061), thus there were
no differences in scores before prompt and after prompt across the three
groups.
Follow up pair wise comparisons for the significant
main effect for group revealed that the WS group scored significantly
lower on the jokes task than the CA control group (F(1, 66)=21.62,
p<0.001) and that the DS group scored significantly lower than the
NCA control group (F(1,66)=32.24, p<.001). However, there was no
significant difference in joke scores between the WS and DS groups
(F(1,66)=3.75, p=0.172) (See Table 2 for mean score differences). All p values were Bonferroni adjusted Table 2.
Note: Mean (SD); MAWS= MA matched controls to WS; MADS= MA matched controls to DS
Clinical groups vs MA matched groups
See Table 1 and Table 2
for means and standard deviations for MA and humour comprehension,
respectively. Correlation analysis revealed that MA was significantly
associated with jokes score before prompt (r=.52, p<.005) and joke
score after prompts (r=0.51, p<0.005) for WS group. Similarly, MA was
significantly and positively associated before prompt joke score
(r=0.56, p<0.05) and after prompt joke score (r=.59, p<.05) for
the DS group and the WSMA controls (before prompt r=0.64, p<0.05;
after prompt r=0.64, p<0.05) but not for DSMA controls before prompt
(r=0.14, p=0.645) or after prompts (r=0.05, p=0.862).
WS vs MA controls
The mean and standard deviations for WS and MA matched controls are presented in Table 2.
A repeated measures ANCOVA comparing the WS group to the WSMA control
group revealed no significant main effect for prompt (F (1, 44)=1.85,
p=0.181) and no significant prompt by group interaction (F(1,44)=1.80,
p=0.187). There was also no significant difference in joke score between
the WS group and the WSMA matched control group (F (1,44) =0.33,
p=0.567.
DS vs MA controls
The results were similar for the DS group compared to
their DSMA matched controls. There was no significant main effect for
prompt (F(1,28)=1.22, p=0.279) and no significant prompt by group
interaction (F(1, 28) =0.83, p=0.316). Furthermore, there were no
significant difference in total joke score between the DS group and the
DSMA matched control group (F (1,28) =0.27, p=0.607). Table 2 for means and standard deviations,
Use of mental state language
A repeated measures ANCOVA with group as a between
subjects' factor (five levels; WS, DS, CA controls, MAWS and MADS) and
prompt as a within subjects' factor (two levels; before prompt and after
prompt) revealed no significant differences in total use of mental
state language see Figure 2
between groups before and after prompt (F (1, 26) =0.46, p=0.503).
Therefore, only the before prompt data was used for the subsequent
analyses Figure 2.
WS vs DS vs CA Controls
Multivariate analysis of covariance (MANCOVA) with
the six different categories of mental state language (emotion, physical
emotion, desire, cognition, pain and character speech) as the dependent
variables and MA as a covariate was conducted to determine if there
were any differences in the proportion of mental state words used by the
three groups (WS, DS and CA matched controls) (Table 3
for descriptive information for each group for each category). The
overall test revealed a significant difference between groups in the use
of mental state language (F(12,122) =2.13, p<0.05). Further
univariate analysis revealed a significant difference between the three
groups in the use of physical emotion words (F (2,66) =6.02, p<0.005)
and cognition words (F(2, 66) =5.28, p<0.005). There were no
significant differences between the three groups in the use of desire
words (F(2,66) =0.55, p=0.581), total emotion words (F(2,66)=.38,
p=0.689), pain related words (F(2,66)=1.59, p=0.211) or character speech
phrases (F(2,66)=0.29, p=0.749). All p values for the uni variate
analysis were compared to the critical a=0.01, adjusted for the multiple
dependent variables.
Follow up pair wise comparisons of the three groups
for physical emotion words revealed that there was a significant
difference in use of physical emotion words between the WS and DS groups
(F(1,66)=11.79, p<0.005), with the WS group using significantly
fewer physical emotion words compared to DS. There were no significant
differences in the use of physical emotion words between the WS and CA
matched control groups (F(1,66)=2.27, p=.411) or between the DS and CA
matched control groups (F (1,66)= 1.87, p=.528). Comparisons for the
cognition words indicated that WS used significantly fewer cognition
words compared to the CA control group (F(1,66)=6.46, p<0.05). The DS
group also used significantly fewer cognition words compared to the CA
control group (F (1,66)=10.21, p<0.05). However, there was no
significant differences in number of cognition words used by the DS and
WS groups (F (1,66)=1.38, p=.735). All p values for the pair wise
comparisons were bonferroni adjusted. Refer to Table 3 for descriptive statistics of mental state language for each group.
WS vs MA matched controls
The MANCOVA revealed a significant difference between
the WS and MA matched control groups on the use of mental state
language (F(6, 39)= 3.79, p<0.05). However, further analysis revealed
that there was no significant difference between groups for desire
words (F (1, 44)=1.46, p=0.233), pain (F (1,44)=1.94, p=0.170), emotion
words (F (1,44)=0.01, p=0.918), physical emotion words (F(1,44)=2.56,
p=0.117) cognition words (F(1,44) = 2.15, p=0.150) or character speech
phrases (F (1,44) = 3.29, p=0.077). All p values for univariate analysis
compared to critical alpha of 0.01, adjusted for multiple dependent
variables. See Table 3 for means and standard deviations.
DS vs MA matched controls
A similar analysis was conducted to compare the DS
and their MA control group. No significant differences were observed in
overall mental state language use between the two groups (F (5,
24)=0.722, p =0.614). See Table 3 means and standard deviations of mental state language use Table 3.
Note: Mean (SD); MAWS: MA Matched Controls to WS; MADS: MA Matched Controls to DS.
Mental State language and humour comprehension
Since there were no significant differences between
groups on either humour comprehension or total mental state language
use, before prompt or after prompt (see above), the following
correlation analysis was also conducted using only the before prompt
data. Correlation analysis was conducted to examine whether any
associations existed in the total use of mental state language and the
score on the picture joke task for each group. There was a significant,
positive correlation between total mental state language use and joke
scores for CA matched controls(r=0.44, p<0.05) and MADS controls
(r=0.58, p<0.05). No significant associations between total mental
state language use and scores on the joke task were found for the DS
group (r=0.13, p=0.628), WS group (r= -0.19, p=0.356) or MAWS group
(r=0.35, p=0.163).
Discussion
The aim of the present study was to examine
differences in humour comprehension and the use of mental state language
in individuals with WS, DS and typically developing CA and MA matched
controls and to explore whether humour comprehension and mental state
language use was related.
Humour comprehension
It was hypothesized that the WS and DS groups would
have lower humour comprehension than CA matched controls, but that no
such differences would exist relative to the MA matched controls. In
accordance with these predictions, WS and DS groups scored significantly
lower than the CA matched control group on the joke task, but there
were no significant differences in humour comprehension between the WS
or DS and MA matched control groups. These findings may be interpreted
to suggest that WS and DS groups understand humour at a level
commensurate with their mental age, but below the level of their
chronological age.
Findings are consistent with Godbee & Porter [26],
which showed that WS children had more difficulty than CA matched
controls, but performed similarly to MA matched children in
understanding non literal language, such as sarcasm, metaphors and
simile. Although, Godbee & Porter [26]
did not directly examine visual humour comprehension, some similar
processes are likely to underlie the comprehension of visual humorous
stimuli.
Both WS and DS are associated with intellectual disability Wang & Bellugi [53], and these conditions are also both associated with executive functioning impairments Carney et al. [54], Zelazo et al. [55], Lew et al. [56].
A possible next step for future research is to explore the relationship
between humour comprehension and executive functions in these
populations.
Use of mental state language
Results revealed no significant difference in the use
of mental state words (in any category) between WS and CA matched
controls; except for the use of cognition words (WS produced fewer).
Results also revealed that the WS group did not differ significantly in
their use of mental state language compared to MA matched controls,
which was in accordance with predictions. These findings suggest that WS
are able to infer mental states from cartoons at the level of CA and MA
matched controls, but had more difficulties with producing cognition
words. Furthermore, there were no significant differences in the use of
mental state language between WS and DS groups, apart from on physical
emotion words (e.g., laughing, crying, screaming). WS used fewer
physical emotion words than DS, which was not predicted.
The DS group also used fewer cognition words than CA
matched controls, which is in accordance with expectations. On the other
hand, the DS group did not differ significantly from MA matched
controls. These findings were consistent with Reilly et al. [44]
who showed that DS used fewer emotional and cognitive language
enhancers whilst telling a story. This finding is also consistent with
Baron-Cohen et al. [37]
who found DS individuals performed at the level of typical controls on
false belief tasks. However, it is not consistent with another study
looking at ToM in DS, which also controlled for MA, and found that DS
performed lower than MA matched typically developing children Giaouri et
al. [57]. The discrepancy is likely due to the type of task used, as Tager-Flusberg & Sullivan [36]
used traditional false belief tasks, where they are explicitly asked
what character thinking is. The present task measured implicit ability
to infer mental state and may have been more subtle.
Humour and mental state language use
Total use of mental state language only significantly
correlated with joke score for CA matched and DSMA matched controls
(for DS), suggesting that humour comprehension was not associated with
ToM abilities in WS or DS. This finding is inconsistent with suggestions
that ToM and humour appreciation are necessarily related. Some jokes in
our set could be described as physical (e.g., girl sitting on a tack),
which may, at least partially account for our findings. Further research
is warranted.
Strengths and Limitations
No previous studies have specifically explored humour
comprehension (in the form of understanding picture jokes) in WS or
DS.A particular strength of this study was that each control participant
was individually matched to either WS or DS individuals on the basis of
mental age. DS and WS participants were also matched on chronological
age (albeit at a group level). That allowed us to control for the
influence of intellectual level and the amount of social experience
gained with age on joke task performance. However, due to WS and DS
often having an uneven cognitive profile, with strengths in some
intellectual domains and weaknesses in others, it is possible that there
still may be differences in some aspects of cognitive ability Jarrold
& Brock [58].
In the present study, there was too much inter-subtest scatter (in the
WJ-R) to be able to individually match on all the different subtests of
the WJ-R and, in turn, the different aspects of intellectual ability
(e.g., verbal comprehension, working memory, and reasoning) were not
controlled. Finally, the sample size of each group was small (albeit
relatively large relative to other studies in the area), so caution
needs to be exercised when generalizing the results to the wider
population [59-65].
Implications and Future research
The results of the current research contribute to the
limited literature on humour comprehension in WS and DS. Humour is
essential for successful social interactions and is considered a
positive attribute Martin [2].
An impairment in humour could lead to poor peer relationships and in
turn, social isolation. Techniques to enhance humour comprehension in
people with WS and DS may be able to aid them in using humour more
effectively during socialization and, in turn, enhance social
interactions. Furthermore, these findings also provide an insight into
the mental processes involved in humour processing and comprehension,
and the results suggest that intellectual ability plays a role.
The results also contribute to the expanding
literature on ToM abilities in WS and DS, specifically about use of
mental state language in WS and DS and the relationship between ToM and
humour understanding. Since WS and DS had more difficulties with
cognition words (e.g., thinks), perhaps these findings could be used to
form a training or therapy program to enhance their ability of inferring
these mental states, for example, via more exposure to this vocabulary
during early childhood, when ToM is still developing. This may also
enhance WS and DS individuals' conversation and social skills.
However, there are still questions about the topic at
hand. Future research should be conducted with a greater number of
participants in each group, with the aim of matching participants on
each dimension of cognitive ability. That would allow use of regression
analyses to examine the main cognitive contributors to the understanding
of humour and, in particular, the role of language and executive
functioning in humour comprehension. Related to this, future research
should include independent measures of language and executive function,
specifically measures of expressive and receptive language, working
memory, reasoning and problem solving abilities.
Future research should also try and examine whether
mode of presentation of humour (e.g. verbally or visually) affects
humour comprehension in these (and other) clinical groups. Furthermore,
data on humour comprehension could be gathered from multiple sources,
such as measuring latencies of time taken to respond, which would reveal
if there are any differences in WS, DS and CA and MA matched controls
in time taken to process the stimuli and the jokes. Additionally, more
research is required to examine how humour comprehension relates to
mental state language in WS and DS, or perhaps whether WS and DS use
different mechanisms to neuro typical individuals for humour
comprehension [66-69].
Conclusion
In conclusion, the results reveal impaired humour
comprehension relative to chronological age matched controls in both WS
and DS, but both clinical groups seem to understand humour equally well
to one another and to typically developing mental-age matched peers.
Furthermore, WS and DS were found to use similar levels of mental state
language, except for cognition words and physical emotion words (e.g.,
laughing). Findings highlight the importance of intellectual ability in
humour comprehension and have implications relating to quality of life
and social experience in WS and DS. Impairments in humour comprehension
can cause difficulties in socializing and, thus, awareness of this
deficit in WS and DS can help enhance their social interactions and
conversational skills. Further research needs to be conducted with
stricter controlling and matching on potentially confounding variables,
such as verbal language abilities and executive functioning to yield a
further understanding.
Acknowledgement
Thank you to participants and to Williams Syndrome Australia Limited and Australian Rotary Health who funded this work.
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