Baron-Cohen et al. (eyes test)

The “Reading the Mind in the Eyes” Test (RMET) shows a photograph of just the eye region and asks what feeling it shows. Simon Baron-Cohen and colleagues devised it.

It is an advanced test of theory of mind: the ability to work out what other people believe, want, or feel.

Psychology Being Investigated

• Autism Spectrum Disorder (ASD): A neurodevelopmental disorder that affects a person’s social and communication skills. Autistic individuals may interpret eye contact, facial expressions, body language, and gestures differently.
• High-Functioning Autism (HFA): A type of autism, considered a milder form, where individuals can still function well in society and cope with daily activities.
• Asperger’s Syndrome (AS): A neurodevelopmental disorder on the autism spectrum that affects a person’s social and communication skills, and is characterized by difficulties with social interaction, understanding non-verbal cues, and repetitive behaviors.
• Theory of Mind: The ability to understand that others have their own mental states, such as desires, emotions, and beliefs, and that these states can be different from one’s own. This ability allows people to explain and predict the actions of others.
• Social Sensitivity: The ability to interpret nonverbal cues, specifically those conveyed through the eyes. The studies examine whether individuals with autism have a difference in social sensitivity compared to neurotypical individuals.
• Read the Mind in the Eyes Test (Revised): Participants were presented with 36 photographs of the eye-region of faces and asked to choose the best word from four options that described what the person in the picture was thinking or feeling.
• Autism Spectrum Quotient (AQ): This was a self-report questionnaire that measured the degree to which individuals possess autistic traits. The test had 50 statements where participants had to agree or disagree. Higher scores suggest the person has more autistic traits. Researchers expect an inverse correlation between scores on the Eyes Test and the AQ.

Background

Theory of Mind and the False-Belief Task

Theory of mind is the ability to attribute independent mental states, such as beliefs, desires, and emotions, to yourself and other people. This lets us explain and predict behaviour. Premack and Woodruff (1978) coined the term while asking whether chimpanzees could infer another animal’s goals.

Wimmer and Perner (1983) turned the idea into a rigorous test for children: the false-belief task. The task is simple. A child watches a story character, “Maxi,” hide chocolate in one place, then leave the room while someone moves it.

To answer correctly where Maxi will look, the child must track his false belief separately from what they themselves know. Most children pass this by age five.

Baron-Cohen, Leslie, and Frith (1985) adapted this into the “Sally-Anne” task to test whether autism involves mind-blindness (Baron-Cohen, 1990), a specific difficulty with theory of mind. Most autistic children in their study failed the false-belief question, even though children with Down syndrome and much younger typically developing children passed.

This suggested the difficulty was specific to mentalising, not simply low IQ.

The Ceiling-Effect Problem

Standard false-belief tasks are pass or fail, and they were built for young children. Able adults pass them easily.

This made the test too easy, producing a ceiling effect: almost everyone scores at the top, so genuine individual differences are hidden. Yet clinicians kept observing that autistic adults who passed these tasks still struggled with the fast, intuitive reading of others in real conversation.

That gap was the practical motivation for an “advanced” measure. Happé (1994) offered one route with the Strange Stories task, understanding non-literal remarks such as lies, jokes and irony.

The Eyes Test was Baron-Cohen’s complementary route: strip away everything except the eyes and force the reader to decode a subtle mental state. Infants attend to eyes and follow gaze long before they can reason about beliefs, so Baron-Cohen argued the eyes offer a privileged window onto intuitive mindreading.

The Original 1997 Eyes Test

In 1997, Baron-Cohen, Jolliffe, Mortimore, and Robertson developed the original Eyes Test. It aimed to assess theory of mind in autistic adults or those with Asperger syndrome.

Participants had to choose the better of two words to describe what the person in the picture was thinking or feeling.

The clinical group scored lower than controls. The basic effect was real. But the design had real weaknesses.

It had only two options to choose from, so chance alone gave 50%. It also used more female than male faces, and some basic emotions that were too easy to identify, sometimes solvable just by reading gaze direction rather than mental state.

There was no glossary, either, so a low score might reflect not knowing a word rather than misreading the eyes. These limitations motivated a thorough revision.

The Revised 2001 Test and How It Is Scored

The 2001 revised version was developed to address the shortcomings of the original test, providing a more reliable and valid measure of social intelligence.

The revised test has four options and a more equal balance of male and female faces.

It also uses harder mental states, plus a glossary.

Take the example above. The target word is “insisting.”

The three foils (“tentative,” “serious,” “cautious”) are all plausible, similarly-toned mental states, so the reader cannot win by spotting an obviously silly wrong answer.

Scoring is simply the number of correct targets out of 36, with no penalty for using the glossary.

With four options per item, the guessing baseline works out at about 25%. That is roughly 9 out of 36 by chance.

Actual group scores run well above this, from 21.9 up to 30.97, showing the scores reflect real mental-state reading rather than luck.

Aims

• To test whether the revised version of the eyes test would work on a group of autistic adults.
• To see whether normal non-autistic females would score higher in the revised eyes test than normal males.
• To investigate if there would be an inverse (negative) correlation between performance on the Revised Eye Test and scores on the Autism Spectrum Quotient (AQ) in a sample of normal adults.

Method

Sample

The study used a combination of volunteer and opportunity sampling techniques.

Group 1 consisted of volunteers who responded to advertisements, while Groups 2 and 3 were recruited using opportunity sampling from community locations.

Group 4 was comprised of randomly selected individuals who matched the IQ of group 1.

Group 1: Adults with Asperger Syndrome (AS) or High-Functioning Autism (HFA)

15 male adults with Asperger’s Syndrome (AS) or High-Functioning Autism (HFA).

They were recruited through advertisements in the UK National Autistic Society magazine or similar support groups, and were diagnosed at specialist centers using established criteria.

The participants had a mean IQ of 115 with a standard deviation of 16.1, which is within the normal range. Their average age was 29.7 years.

Group 2: General Population Control Group

This group consisted of 122 adults from the general population.

They were recruited from adult community and education classes in Exeter and public library users in Cambridge.

They had a broad mix of occupations and educational backgrounds.

Data on age was available for 88 of these participants. The mean age was 46.5 years.

This group served as a control group to compare the performance of individuals with autism with those without.

This group did not take the Autism Spectrum Quotient (AQ) test.

Group 3: Student Control Group

This group comprised 103 undergraduate students from Cambridge University.

There were 53 males and 50 females in this group.

The students were assumed to have a high IQ due to the stringent entrance requirements of the university, and their IQ was not tested.

The mean age of this group was 20.8 years.

This group was a control group used to compare the experimental group with a group of high IQ individuals.

Group 4: IQ-Matched Control Group

This group consisted of 14 randomly selected adults from the general population, matched to Group 1 on IQ.

The mean IQ of this group was 116, with a standard deviation of 6.4, closely matching Group 1’s mean IQ.

The mean age of this group was 28 years.

This group was included to control for the possible influence of intelligence on theory of mind test performance.

This was a matched-pairs design group. Participants in different groups were paired on a relevant variable, here IQ, so group differences on the outcome could not simply be explained by that variable.

Design

The 2001 study used a quasi-experimental design with a closed questionnaire, incorporating independent groups and matched pairs, along with a naturally occurring independent variable.

This design allowed researchers to investigate the relationship between autism, theory of mind, and social intelligence, while controlling for factors such as IQ and gender.

The design also had a correlational element. For the sample that completed both tests, Eyes Test scores were compared against Autism Spectrum Quotient (AQ) scores.

The two dependent variables were therefore the Eyes Test score, out of 36, and the AQ score.

Independent variable

The independent variable (IV) was whether participants had Asperger Syndrome (AS) or High-Functioning Autism (HFA) or were neurotypical.

This was a naturally occurring variable, meaning the researchers did not manipulate it, but rather grouped participants based on their pre-existing condition.

The IV had four levels:

1. Adults with AS/HFA (Group 1)
2. Neurotypical adults from the general population (Group 2)
3. Undergraduate students (Group 3)
4. IQ-matched controls (Group 4)

Gender was also considered as an independent variable.

Dependent variable

The study aimed to investigate theory of mind, but it did not measure theory of mind directly.

Instead, scores on the Revised Eye Test and the Autism Spectrum Quotient (AQ) test served as indicators of a participant’s ability to read others’ mental states. The RET score ran from 0 to 36.

Participants who scored highly showed good social sensitivity and a well-developed theory of mind.

AQ scores worked the other way: higher scores meant more autistic traits.

Procedure

1. Development of the Revised Eyes Test:

• Two of the experimenters created the target words and foils.
• The items were then piloted on eight judges.
• For a target word to be considered suitable, at least five out of the eight judges had to agree that it was the most appropriate descriptor for the emotion shown in the eyes.
• Additionally, no more than two of the eight judges could pick the foil.
• Items that did not meet these criteria were revised by creating new target words and foils.
• The revised items were then re-assessed by the judges until the item “passed” the criteria.

This process ensured the target words were the most appropriate descriptors for the emotions shown in the eyes. It also ensured the foil options were not easily confused with the target.

2. Administration of Tests:

The procedure was designed to measure the ability to recognize and interpret mental states based on cues from the eyes and to assess the level of autistic traits in the participants.

The tests were administered by trained researchers in a standardized way.

The tests were administered individually in a quiet room at either Cambridge or Exeter University.

There was no time limit for completing the tests.

Each participant completed a practice test before starting the main tests

Participants were given a glossary of terms and could ask for clarification. They were allowed to use the glossary during the test.

3. Revised Eye Test:

• Participants were presented with 36 sets of eyes.
• Each set consisted of a black and white photo of the eye region of a face.
• For each set of eyes, participants were given four words to choose from: one target word (the correct answer) and three foil words (incorrect answers).
• Participants were asked to choose the word that best described what the person in the photograph was thinking or feeling.
• The foil words were chosen to be similar in valence or intensity to the target word but had different meanings.

4. Autism Spectrum Quotient (AQ) Test:

Participants in Groups 1, 3, and 4 completed the AQ test.

The AQ test is a self-report questionnaire designed to measure the degree to which an individual possesses autistic traits.

The test consists of 50 statements that participants rate on a binary scale (agree or disagree).

5. Gender Identification for Group 1:

Group 1 participants also had to identify the gender of the person in each eye photograph, as a control task. A control task is a secondary measure included to rule out an alternative explanation for the results.

If they could not do this easy task, the test results might be affected by vision, and not theory of mind.

Results

Aim 1: The Autism Deficit

Aim 1: To test if the revised version of the Read the Mind in the Eyes Test would be successful at differentiating participants with AS or HFA (High Functioning Autism) from the general population.

The AS/HFA group scored significantly lower on the Eyes Test than the other three groups. Their mean score was 21.9 out of 36, against control means ranging from 26.2 to 30.97.

This supported the idea that autism involves a specific difficulty reading mental states from the eyes, not a general problem with emotion. The deficit was specific.

The AS/HFA group performed normally on a gender-identification control task, showing the lower Eyes Test scores reflected difficulty reading mental states, not a basic problem with vision.

Group 4 was matched to Group 1 on IQ yet still scored higher, showing the deficit was not explained by general intelligence.

Aim 2: The AQ Correlation

Aim 2: To test if there is an inverse (negative) correlation between performance on the revised Eyes Test and scores on the Autism Spectrum Quotient (AQ) in a sample of normal adults.

The study found a significant negative correlation (-0.53) between scores on the Eyes Test and the AQ test across all groups.

This means participants with more autistic traits, shown by higher AQ scores, tended to read the eyes less accurately. The reverse was also true.

This pattern held across the groups that took the AQ (Groups 1, 3 and 4); Group 2 never completed it, so the correlation comes from the groups that did.

It fits a wider idea: autism sits at one end of a continuous dimension of social cognition, rather than being a separate, all-or-nothing category.

Aim 3: The Sex Difference

Aim 3: To test if non-autistic females would score higher on the revised Eyes Test than non-autistic males.

Among neurotypical adults (Groups 2 and 3), females scored higher than males.

In the student group, for example, women averaged 28.6 versus 27.3 for men.

This difference is small. Baron-Cohen links it to his empathising-systemising theory of sex differences.

Later research has produced mixed replications of it: the finding is consistently small, and it sometimes fails to reach statistical significance in individual samples.

That does not undo the pattern, but it is a reason to treat the size of the sex difference cautiously rather than as a fixed, guaranteed effect. Readers should treat it as a modest average difference between groups, not a rule that applies to every individual.

Conclusion

• The revised eyes test (2001) replicated the findings of the original eyes test (1997).
• Normal females are able to judge emotions better than normal males.
• Neurotypical females tended to score higher than males on the Eyes Test, a small but consistent finding.
• The AQ Test and eyes test are inversely (negatively) correlated. These findings support the idea that autistic traits are related to impaired theory of mind.

Strengths

1. Improved Validity

The revised “Reading the Mind in the Eyes” test was developed to fix four specific flaws in the 1997 original.

• Response options: Four choices replaced two, cutting the chance of guessing correctly from 50% to 25%.
• Complex mental states: Only difficult, complex mental states were used, removing the easy items that had caused a ceiling effect.
• Glossary: A glossary of terms meant a wrong answer reflected misreading the eyes, not simply not knowing a word.
• Gender balance: An equal number of male and female faces replaced the original’s female-heavy set.

These changes helped increase the validity of the test as a measure of social intelligence and theory of mind.

2. Controlled Experiment

The study used a quasi-experimental design, which gave researchers some control over variables. That boosts confidence in the results. Specifically, researchers could be more confident that group membership, the independent variable, affected Eyes Test scores.

Random allocation was not possible, since group membership could not be assigned. Researchers instead controlled for other factors, such as matching the IQ of the autism group to one of the control groups.

IQ turned out not to matter.

The IQ-matched group ruled out intelligence as an explanation for the results. Eyes Test scores showed no correlation with IQ, supporting that the deficit is independent of general intelligence.

3. Rigorous Construction and Strong Controls

The item-construction process was rigorous. A word only became the correct target once at least five of eight judges agreed on it, and no more than two picked any single foil.

This matters because it gives each item a defensible “correct” answer, not one the researchers simply decided on themselves.

Two further design features isolated the construct being measured. The IQ-matched control group (Group 4) ruled out general intelligence as an explanation for the autism group’s lower scores, while the gender-identification control task ruled out basic face perception.

Testing individually in a quiet room, with a practice item and no time limit, also made the procedure easier to repeat.

Weaknesses

1. Low Ecological Validity

The most prominent weakness is low ecological validity: the extent to which a test’s findings reflect how a process actually works in real life.

The Eyes Test relies on static images of eyes to assess theory of mind. Real life is not static.

In real life, people read emotion from dynamic cues instead: body language, facial expressions, tone of voice, and situational context.

This means the test might not fully reflect how people interpret emotions in everyday interactions. Everyday cues are missing.

Reducing emotion recognition to a still photograph makes it an artificial task that may not mimic real social interaction.

The AQ, being a self-report questionnaire, adds a further limit: participants may give socially desirable or untruthful answers, reducing ecological validity further.

2. Limited Generalizability

The sample size of the autistic group was small (only 15 male adults).

This small sample makes it difficult to generalize the findings to the larger population of individuals with autism spectrum disorder (ASD).

The autistic sample was exclusively male, so the results cannot be generalized to females with autism.

The study also lacks representation from children with autism.

The study was conducted only in the UK, limiting the generalizability of the findings to other cultures where emotional expression might be interpreted differently.

3. Limited Data

The study relies entirely on quantitative data, specifically scores from the Revised Eye Test and the Autism Spectrum Quotient (AQ) test.

This means there is a lack of qualitative data, so there is no insight into the reasons behind the participants’ choices or thought processes.

The use of a close-ended questionnaire does not provide insight into the participants’ reasoning.

It also does not allow for in-depth analysis or understanding of the cognitive processes behind the results.

4. Potential for Guessing

While the revised test reduced the chance of guessing compared to the original version, there was still a one in four chance of participants guessing the correct answer.

This could affect the validity of the results. With four options, the guessing baseline works out at about 25%, or roughly 9 out of 36 items correct by chance alone.

Actual group scores were well above this, from 21.9 up to 30.97, showing the scores reflect real mental-state reading rather than luck.

5. What Does the Test Actually Measure?

The most debated criticism is construct validity: whether the Eyes Test actually measures theory of mind at all.

Real mentalising means representing someone’s beliefs and intentions in context. Matching one word to a pair of eyes may instead tap a narrower, more perceptual ability, such as emotion recognition or vocabulary for emotion words.

It did not measure this directly.

A broader criticism (Frith & Happé, 1994) is that a theory-of-mind deficit cannot explain the whole of autism. It does not account for non-social features, such as restricted interests or a bias toward local detail over the “big picture.”

Their weak central coherence account describes this instead. On this view, the Eyes Test illuminates one important but partial piece of the autistic profile, not the whole picture.

6. Contemporary Research

A 2025 systematic review and meta-analysis (Cusson et al.) asked whether autistic people really show an empathy deficit, and whether the answer depends on which test is used.

The team pooled 226 studies (13,278 autistic and 44,218 typical participants), the largest evidence base yet assembled on the question.

Separate meta-analyses compared cognitive empathy (tasks like the Eyes Test), affective empathy (responding with an appropriate feeling), and scores that collapse both into one number.

Quality was checked against the highest-rated studies alone.

Autistic participants scored significantly lower on cognitive-empathy tasks, of which the Eyes Test is the best-known example, and the effect was large (g = -0.85).

The gap on affective empathy was much smaller and stopped being significant once only the highest-quality studies were included.

Mixed measures inflated the gap the most.

Cusson et al. (2025) concluded that autistic people do show a real, robust difficulty on cognitive-empathy tasks such as the Eyes Test.

But treating “empathy” as one single deficit, as many popular accounts do, makes the true picture look both simpler and larger than it really is.

Ethics

Participants, especially those with AS/HFA, may have felt psychological distress by not understanding the emotions in the eyes.

Some participants, particularly in the autistic group, did not submit their AQ test papers, which may suggest feelings of distress or shame associated with having their autistic traits measured.

This may indicate that the process of testing for autistic characteristics might have caused them some level of distress.

Issues and Debates

Real-World Applications and Uses

The Revised Eyes Test is widely used as a research and screening tool for social cognition, not a stand-alone diagnostic instrument.

A low score can flag mindreading difficulties.

The test is often used alongside the AQ to profile where someone sits on empathy and autistic traits.

Beyond clinical groups, the female advantage on this test became one strand of evidence for Baron-Cohen’s empathising-systemising theory. It frames autism as an extreme version of a cognitive profile that is, on average, more typical of males (Baron-Cohen, 2002).

It also travels well beyond autism.

Because it needs little language, it has also been used to study mental-state reading in schizophrenia, eating disorders, and mood or anxiety disorders.

Performance also tends to decline with normal ageing.

A child-friendly version exists, and the test has been translated into many languages for use around the world.

Individual vs. situational explanations

The study does not completely rule out situational factors, but it emphasises individual traits in explaining differences in emotion-reading ability.

The standardised procedures, matched-pairs design, and consistent findings across groups all point the same way. The ability to read emotions looks like an individual trait, not a product of the situation. Nurture still plays a role.

This does not mean nurture has no influence on social skills or theory of mind. Therapy may still help autistic people build these skills.

But the study itself focuses on theory of mind as an individual trait and ability.

Reductionism vs. holism

The study focuses on the ability to recognize mental states solely from images of the eyes.

This is a very narrow aspect of social interaction, which typically involves many other cues, including body language, tone of voice, and context.

By isolating this one element, the researchers reduce the complexity of social cognition to a single variable that can be easily measured.

How the Eyes Test Compares to Other Theory-of-Mind Tests

The Eyes Test is one of a family of “advanced” theory-of-mind tasks, each probing a slightly different skill. False-belief tasks (Wimmer & Perner, 1983; Baron-Cohen, Leslie, & Frith, 1985) test cognitive ToM: representing that someone holds a false belief.

They are pass or fail, which suits young children, but able adults pass them easily. The Eyes Test was built to beat that ceiling.

Strange Stories (Happé, 1994) instead has people explain non-literal remarks, such as lies, jokes and irony, which taps mental-state reasoning through language. Faux pas recognition asks people to spot when a character has unknowingly said something hurtful.

The Eyes Test leans toward affective ToM, reading how someone feels, rather than cognitive ToM, reasoning about what they believe.

That is its strength. It detects subtle emotion-reading difficulties that belief tasks miss.

It is also the basis of the criticism that the test may measure emotion recognition rather than theory of mind proper.

References

Baron-Cohen, S. (1990). Autism: A specific cognitive disorder of “mind-blindness”. International Review of Psychiatry, 2(1), 81–90. https://doi.org/10.3109/09540269009028274

Baron‐Cohen, S., Wheelwright, S., Hill, J., Raste, Y., & Plumb, I. (2001). The “Reading the Mind in the Eyes” test revised version: A study with normal adults, and adults with Asperger syndrome or high‐functioning autism. Journal of Child Psychology and Psychiatry, 42(2), 241-251.

Baron-Cohen, S. (2002). The extreme male brain theory of autism. Trends in Cognitive Sciences, 6(6), 248–254. https://doi.org/10.1016/S1364-6613(02)01904-6

Baron-Cohen, S., Jolliffe, T., Mortimore, C., & Robertson, M. (1997). Another advanced test of theory of mind: Evidence from very high functioning adults with autism or Asperger syndrome. Journal of Child Psychology and Psychiatry, 38(7), 813–822.

Baron-Cohen, S., Leslie, A. M., & Frith, U. (1985). Does the autistic child have a “theory of mind”? Cognition, 21(1), 37–46. https://doi.org/10.1016/0010-0277(85)90022-8

Cusson, N. M., Meilleur, A. J., Bernhardt, B. C., Soulières, I., & Mottron, L. (2025). A systematic review and meta-analysis of empathy in autism: The influence of measures. Clinical Psychology Review, 120, Article 102623. https://doi.org/10.1016/j.cpr.2025.102623

Frith, U., & Happé, F. (1994). Autism: Beyond “theory of mind”. Cognition, 50, 115–132.

Happé, F. (1994). An advanced test of theory of mind: Understanding of story characters’ thoughts and feelings by able autistic, mentally handicapped and normal children and adults. Journal of Autism and Developmental Disorders, 24, 129–154.

Premack, D., & Woodruff, G. (1978). Does the chimpanzee have a theory of mind? Behavioral and Brain Sciences, 1(4), 515–526. https://doi.org/10.1017/S0140525X00076512

Wimmer, H., & Perner, J. (1983). Beliefs about beliefs: Representation and constraining function of wrong beliefs in young children’s understanding of deception. Cognition, 13(1), 103–128. https://doi.org/10.1016/0010-0277(83)90004-5

Keep Learning

To help reinforce your understanding and prepare for potential exam questions, here are some practice questions related to this study for AICE Psychology:

Recall and Description:

1. From the study by Baron-Cohen et al. (eyes test):
   • Identify the sampling technique used to recruit the AS/HFA group in this study.
   • State the number of participants diagnosed with AS/HFA in this study.
   • Identify three features of the sample used for Group 4.
   • Name the test that was being revised in this study.
   • Outline one aim of this study.
   • Describe the original version of the ‘Reading the Mind in the Eyes’ test.
   • Describe the procedure of the eyes test.
   • Describe how the target words and foils were developed for the revised ‘Reading the Mind in the Eyes’ test.
   • Describe the theory that Baron-Cohen et al. were testing with their ‘Reading the Mind in the Eyes’ Test.
   • The AS/HFA participants were the only group asked to make two judgments about each photograph. One of these judgements was about the emotion in the photograph. Name the other judgement this group was asked to make about each photograph.
   • Identify the two ways that the revised eyes test increased the range of scores a participant could obtain.
2. From the study by Baron-Cohen et al. (eyes test), outline one result from this study. Refer only to results from the eyes test in your answer.
3. From the study by Baron-Cohen et al. (eyes test):
   • Outline one result in relation to the Autism Spectrum Quotient (AQ).
   • Outline one result comparing the participants of Group 1 to the participants of Group 2. You must use data in your answer.

Application and Evaluation:

1. Two friends, Danilo and Noah, are discussing the validity of the study by Baron-Cohen et al. (eyes test). Danilo thinks the study has validity, but Noah thinks the study does not have validity. Explain one reason why Danilo is correct and one reason why Noah is correct, using evidence from this study.
2. Evaluate the study by Baron-Cohen et al. (eyes test) in terms of two strengths and two weaknesses. At least one of your evaluation points must be about generalizations or the use of self-reports.
3. Outline one methodological strength of this study.
4. Outline one ethical weakness of this study.
5. Suggest one real-world application based on the results of this study.
6. Explain one useful application of the findings, if child participants were used in this study.
7. Explain how one finding from the Baron-Cohen et al. study (eyes test) supports one of the assumptions of the cognitive approach.
8. The study by Baron-Cohen et al. (eyes test) used adult participants, although similar studies have used children. Describe one methodological problem that could arise if child participants were used in this study.

Study Summary Sheet

Original Journal Article