If a participant has a higher score on the eye roll test (meaning they are more susceptible to hypnosis), then they are more prone to experiencing the rubber hand as their own because their sense of subjective ownership of their body can be more easily disrupted.

The Eye Roll Test (Spiegel Test) is a validated assessment tool to measure the hypnotizability of an individual. The test is scored between 1-4, with 1 being less prone to hypnosis and 4 being most prone.  

The Rubber Hand Illusion, developed about 25 years ago, helped scientists understand how our brains use a combination of sight and touch to experience our body as our own.  In this illusion, a rubber hand is placed on a table and stroked at the same time as the participant's hand. Eventually, some participants will begin to experience the rubber hand as their own.

We were interested to see if a person's hypnotizability correlated with the likelihood that their brain could be "tricked" by the Rubber Hand Illusion.   

We performed the Eye Roll Test on students at our school from grades 6 to 8 with 15 male and 15 female from each grade. We discovered that in our school, the grade 8 boys and girls scored an average of 2.6. The grade 7 boys scored an average of 2.9, and the girls scored an average of 2.6. Finally, the grade 6 boys scored an average of 3.2, and the girls scored an average of 3. There was a general trend of students being less prone to hypnosis with increasing age.  

We then performed the Rubber Hand Illusion test. We relied on student reporting as to whether the Rubber Hand Illusion was successful in creating the feeling that the rubber hand was part of their own body. We would continue stroking the rubber hand and stop stroking the student's hand (which was out of their view). If the student continued to experience the feeling of their hand being stroked, it was counted as a positive result.  We created a graded scoring system from 1-4 (low to high) for the students to rate how strongly they experienced the rubber hand as being their own.

We also consulted with a Neuropsychiatrist to learn how the brain gets tricked and why. He taught us that when we conduct the Rubber Hand Experiment, our brain can be tricked into adopting the rubber hand as its own through a combination of sight and feel, especially if a person is prone to hypnosis.

When we tested participants who scored 1 on the eye roll test, they never experienced the rubber hand as their own. In contrast, most students who scored 4 on the Eye Roll Test experienced the rubber hand as their own. There was a general trend that showed that the higher the Eye Roll Test score, the more likely a positive result on the Rubber Hand Illusion.  We will review this more in the observations and analysis section.

Independent Variable: Eye Roll Test

Dependent Variable: Rubber Hand Illusion 

Materials:

rubber hand

table cloth

divider

two paintbrushes

1. Perform Eye Roll Test on participant, scoring between 1-4 based on a reference chart.

2. Perform the Rubber Hand Illusion as follows:

a. Place a divider on the table, dividing it in approximately 2/3.

b. Seat the participant so they can only see the larger part of the table, placing one hand on either side of the divider.

c. Position the rubber hand in front of the participant, next to the divider, in order to imitate their hand behind the divider.

d. Using 2 paintbrushes, stroke a finger of the participant's hand while simultaneously stroking the same finger on the rubber hand, while the participant observes the rubber hand being stroked.  Ask the participant to tell you when they can no longer feel their hand being stroked.

e. When the participant's hand behind the divider begins to twitch, stop stroking the participant's hand, but continue to stroke the rubber hand.  Do not tell the participant you have stopped stroking their hand.

On the Eye Roll Test, we observed that students' hypnotizability diminished with increased age.  Grade 6 students scored highest on the Eye Roll Test, and Grade 8 students scored lowest on the Eye Roll Test.  Females in Grades 6 and 7 scored lower than their male counterparts.

On the Rubber Hand Illusion, students with a high Eye Roll Test score were more likely to experience the rubber hand as their own.  No student with an Eye Roll Test score of 1 experienced the rubber hand as their own.  Conversely, most students with an Eye Roll Test score of 4 experienced the rubber hand as their own.

Our analysis of the Eye Roll Test is in keeping with other reports of hypnotizability diminishing with age. Grade 6 students scored the highest on the Eye Roll Test, whereas Grade 8 students scored the lowest. Interestingly, females were less hypnotizable than their male counterparts in Grades 6 and 7. This might be as a result of earlier maturation of the female brain.

Our analysis of the comparison of the Eye Roll Test and the Rubber Hand Illusion demonstrated a correlation between hypnotizability and susceptibility to the participant experiencing the rubber hand as their own. Hypnosis involves a disruption in the brain's sense of ownership over the body.  We would thus expect that a participant who is not prone to hypnosis would not be prone to their brain being "tricked" into experiencing a foreign hand as a part of the body.  Conversely, someone more prone to hypnosis would be susceptible to experiencing something foreign as self.

We concluded that: 

1) Hypnotizability diminishes with age, between grades 6 and 8

2) Hypnotizability correlates positively with a participant experiencing the rubber hand as their own during the Rubber Hand Illusion

The positive correlation between the Eye Roll Test and the Rubber Hand Illusion provides interesting insights into how our brain can be "tricked" into believing that a foreign hand is a part of the body, and that this susceptibility is related to hypnotizability.  

This finding has potential applications in the field of rehabilitation. In recent years, virtual reality technology has been use to allow patients to recover more quickly from injuries such as stroke. This technology relies on the ability of the brain to be "tricked" into believing that an artificial environment is in fact real. Assessing hypnotizability in patients may help select those who are most likely to benefit from these rehabilitation techniques.

Likewise, the fields of robotics and augmented reality are integrating the ability for devices to become extensions of our minds. Famous projects like the Canadarm and NeuroArm (invented by a Calgary neurosurgeon) involve scientists using robot arms, as though they were their own, to manipulate payloads in outer space or surgical tools within a brain. 

1. We only tested our school, which may not be similar to a random sampling of the population. 

2. We only tested students from Grades 6-8. The trends that we saw in susceptibility to hypnosis may not extrapolate to younger or older individuals.

3. We relied on subjective reporting of participants.

Rubber Hand Illusion photo by: https://clairelevans.substack.com/p/out-of-body-out-of-office

Eye Roll Test image by: https://hypnotechs.com/resources/spiegel-test

We would like to thank Dr. Aaron Mackie for explaining to us the amazing science behind our experiment.

We would also like to acknowledge all the willing anonymous participants from our school for helping us gather our data.

And finally, thank you Mr. Cassidy for giving us your support for our first Science Fair!