First task which I have chosen is mental rotation. Why? Because it was very good described and I thought that it is a good starting point for my research.
Description of the task
Mental rotation task is the task where we have to represent the image and generate our mental representation of it. The subject see two forms which are rotated by some degree and he has to decide whether are these forms same or the mirror images.
Previous research
Shepard and Metzler (1971) introduced the concept of mental rotation and confirmed that there is an increasing linear relation between reaction times and angular disparity between the two stimuli. These finding confirmed the Shepard's hypothesis that the menatal rotation is represented in analog format (as we see the image) and is rotated by unitary process (holistic theory). The second analog theory is a "piecemeal" theory presented by Kosslyn (1981) which proposes that the image is first divided into parts and afterwards is each part rotated sequentialy. Besides these analog theories there exists also propositional theory which supposes that the image is representated in the abstract propositional format. Both piecemeal theory and propositional theory predict that there will be an increase in the reaction time while the stimuli difficulty is increasing.
Pic 1: Mental rotation task (Shepard and Metzler)
Five stages of mental rotation process were described:
- stimulus coding
- generation of the mental image
- mental rotation and matching
- decision whether the stimuli and mental image are matching or not
Afterwards huge amount of research was done comparing reaction times and error rates between different groups of people (women vs. men, nationalities, artists vs.nonartist, whether mental rotation abilities predict choice of field of surgery etc.).
Experiments with EEG (Gill et al.,1998) confirmed componential aspects of the mental rotation and localized corresponding regions of the brain. Rotation of an internal image may be mediated by the left temporal region.
Neuroimaging studies have showen that the mental rotation is mediated primarily by parietal lobes. O'Boyle et al. (2005) demonstrated in their fMRI study that mathematically gifted male adolescents engage different brain structures than those avarage gifted when performing 3D mental rotation.
Pic 2: Brain activity during the mental rotation task
My stimuli
A set of special stimuli with different complexity was created. Each stimulus consists of basic units (squares or cubes). We presented 228 pairs of 2D stimuli and 140 pairs of 3D stimuli (rotated by multiple of 60°) with an increasing complexity. 3D stimuli were composed so that rotation around different axis was needed.
Pic 3: My 2D and 3D stimuli used for MR task
After reaching the highest complexity (2D stimuli) we added stimuli with modifications and observed whether there is an increase in error rates. (it means that the minor sign was mirrored while the major sign was normal - it could confuse subjects and they could say that stimuli are same).
Pic 4: Example of mental rotation task - pair of 2D stimuli without modifications(A) and with modification in the minor sign(B)
Why I've decided to create this new set of stimuli? Because I needed some very well descriable stimuli where I can do simple modifications. I also wanted to have the same objects in 2D and 3D.
Experiment
1,During the whole experiment the EEG activity was measured.
2,Mental rotation task
- First was measured the baseline activity during closed and opened eyes and blind stimuli were presented
- Example stimuli for 2D
- Mental rotation task with 2D stimuli with an increasing complexity
- Example stimuli for 3D
- Mental rotation task with 3D stimuli
3, Questionnaire which asked subjects what strategies they had used, what is their mathematical education and abilities, sex, health, which food additives, nootropics or psychopharmaca they intake
4, Intelligence test - Raven (WAIS IV would be better, but this was used because it is easier and it is the entering test to Mensa)
5, Analysis of reaction times and error rates
6, Processing and analysis of an EEG signal
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