Another advanced test of theory of mind: evidence from very high functioning adults with autism or Asperger Syndrome

Baron-Cohen et al (1997) (Summary)

Abstract

The study investigated theory of mind in adults with autism and Asperger Syndrome.

In previous studies these people passed second-order theory of mind tests, although the tests were designed for those with a mental age of up to 6 years. Therefore the task used in this study was designed for very high functioning adults and required them to identify the mental state of a person based on photographs of the person's eyes.

Participants were matched on age and completed the eyes test and Happé's strange stories task (both second-order theory of mind tests), along with two control tasks: recognising gender from the eyes and recognising basic emotions from the whole face.

Participants with autism or Asperger Syndrome performed significantly worse than controls on the theory of mind tests, but were not impaired on the control tasks, suggesting there are subtle mind reading deficits (lack of theory of mind) in high functioning adults with autism or Asperger Syndrome.

Background

Previous research has shown that most children with autism have impairments in developing a theory of mind and are unable to pass second-order theory of mind tests: these ask the participant to identify what one person thinks about another person's thoughts. This may be the underlying cause of the social, communicative and imaginative difficulties that are part of the diagnostic criteria for autism (autistic spectrum disorder, DSM-IV, APA, 1994).

However, Bowler (1992) found that adults with Asperger Syndrome are able to pass second-order theory of mind tests. Individuals with Asperger Syndrome have the same social and communicative symptoms of autism but without the language delay. Ozonoff et al (1991) also found that adults with 'high-functioning autism' or Asperger Syndrome could pass second-order theory of mind tests.

As these tests were all developed to assess second-order theory of mind based on the expected level for a 'normal' 6 year old child (or first-order theory of mind in a 'normal' 4 year old) it is impossible to conclude that adults who pass the tests have an intact theory of mind.

Happé (1994) conducted a study where adults with autism or Asperger Syndrome were given a story comprehension task, with two conditions: questions about character's mental states (experimental condition) and questions about physical events (control condition). Compared to the age-matched control group, the participants had more difficulty with the mental state stories.

Baron-Cohen et al's study uses the 'Reading the Mind in the Eyes' Task (Eyes Task), which involves understanding mental state terms and matching them to parts of faces. In each case the participant is given two mental state terms, which are basic (happy, sad, afraid etc.) or complex (reflective, arrogant, scheming etc.). The forced choice method was used at it had been used successfully in previous research.

Three groups of participants took part in the study:
Adults with Tourette Syndrome were used for comparison as this is also a developmental disorder with genetic factors, causes disruption to normal schooling, peer relations and affects more males than females. All of these factors are true for autism and Asperger's Syndrome, as is the presence of frontal abnormalities in the brain (although they differ for each disorder).

To assess the validity of the Eyes Task, participants completed Happé's Strange Stories test as well as two control tasks. The researchers also investigated gender differences in emotion recognition with a large sample of 'normal' males and females separately. This last part of the study comes from the lack of previous tests of gender differences in emotion recognition due to tests not measuring subtle differences, even though 'folk psychology' suggests these gender differences do exist. The Eyes Task provided an opportunity to test this assumption.

Subjects

Group 1
  • 16 adults
  • 4 with higher function autism (HFA) meeting DSM-IV criteria
  • 12 with Asperger Syndrome (AS) meeting ICD-10 criteria
  • 13 males, 3 females
  • All of 'normal' intelligence
  • Recruited from clinical sources and an advert in the National Autistic Society magazine 'Communication'.
Group 2
  • 50 adults matched on age
  • 25 males, 25 females
  • drawn from local population of Cambridge (no members of the university)
  • no history of psychiatric disorder (based on self report)
  • selected randomly from a panel
  • assumed to be of 'normal' intelligence
Group 3
  • 10 adults with Tourette Syndrome (TS) meeting DSM-IV criteria
  • matched on age to experimental group
  • 8 males, 2 females
  • recruited from a referral centre in London
IQ for 3 Groups
IQ Results
 


Groups 1 and 3 were intelligence tested using the Wechsler Adult Intelligence Test (WAIS-R) and were of normal IQ (85 or above). They also had to pass the first-order and second-order theory of mind tests mentioned above.

Methodology

Mental State Terms
Eyes Task eg 3
Eyes Task eg 4
Eyes Task eg 1
Eyes Task eg 2
Procedure
Each subject completed all four tasks in a random order.

Eyes Task
The Eyes Task consisted of 25 photographs (taken from magazines) of the eyes region of the face, standardised to the same size, with a forced choice of two mental state terms printed under the photograph.

The experimenter asked the subject "Which word best describes what this person is feeling or thinking?". Maximum score: 25.

The mental state terms were generated by a panel of 4 judges (2 male, 2 female) and then tested with a panel of 8 judges (4 male, 4 female) who were unaware of the purposes of the study, with unanimous agreement on the target words. The list included both basic and complex mental terms.

The task was designed to be a pure theory of mind test, as it involves no other cognitive functions (planning, context, attention switching etc.).


Basic Emotion Recognition Task eg 1
Basic Emotion Recognition Task eg 1
Strange Stories
To assess the validity of the test the participants were also assessed on Happé's Strange Stories task (the AS and HFA groups separately in a study by Joliffe, 1997) - if valid then the results between the two tasks should correlate.

Gender Recognition Task
The same sets of eyes were used as in the experimental condition.

Participants had to identify the gender of the person in each photograph, which is a social judgment that does not involve mind reading, used to check whether any errors were due to general difficulties with face perception, perceptual discrimination or social perception. Maximum score: 25.

Basic Emotion Recognition Task
This involved judging faces on 6 basic emotions: happy, sad, angry, afraid, disgusted and surprised. This was used to assess whether any deficits were due to a lack of basic emotion recognition.


Results

Eyes Task Results Table 3
Eyes Task Results Table 4
Both the normal and TS groups performed similarly, with a mean of 20.3 for the normal group and 20.4 for the TS group. The mean for the experimental group was 16.3.

Females performed better than males (21.8 for females, 18.8 for males).

All groups performed similarly on the gender control task (highest mean for experimental group - 24.1).

The results for the three groups were analysed using independent t tests (statistical analysis), as were the results for each group on the experimental task and the gender control task, and also the scores for females and males.

The difference between the experimental and control groups is statistically significant, as is the difference between females and males and between the experimental group and males.

Overall only half of the experimental group performed better than they would by chance, whereas all of the controls performed better than chance.

There was no correlation between IQ and performance on the Eyes Task.

On Happé's Strange Stories, the experimental group were significantly impaired (Joliffe, 1997) compared to the TS group.


Discussion

The predictions made were confirmed: adults with HFA or AS were impaired on subtle theory of mind tests and normal females also performed better than normal males.

These results appear valid for a number of reasons:
The researchers highlight that the study lacks ecological validity, as it is simpler than the demands of real life and uses static cues. They suggest an alternative would be to use movie footage, and report anecdotally that the subjects often report that going to the cinema is a frustrating experience, as the action moves too fast, it is difficult to work out characters’ motivations or to understand why the audience laughs at particular points during the movie.

However, using movie footage would involve other cognitive processes (central coherence and executive function) and is therefore not a 'pure' theory of mind test.

The results of the Eyes Task are similar to previous studies, where toddlers with autism demonstrate they are unable to interpret gaze direction as a way of understanding attention. Young children with autism also show this difficulty in interpreting a person's goals and desires or as an indication of thinking.

The gender differences are interesting, as they have not been scientifically established before, although may be due to genetic or socialisation factors - an area requiring further investigation. They may also reflect gender differences in the rates of development for different cognitive functions - these have already been demonstrated in relation to language development and spatial skills (females are superior in language development, males superior in spatial skills development).