My Master’s project in the School of Psychology at Bangor University aimed to isolate the neural correlates of the Light Source Bias - a bias in visual perception that leads people to assume that light comes from an above-left position of the apex of an object, and is thought to result from hemispheric asymmetry. Hemispheric asymmetry means that one side of the brain is specialised to perform certain functions and therefore dominates the other side during normal processing. A well-known example of hemispheric asymmetry is language function, which is lateralised to the left hemisphere.
There is evidence to suggest that the Light Source Bias is right-lateralised, particularly in young, Western adults, and that this bias decreases with age. If age-related changes do exist, it may signal pathological ageing processes, and therefore understanding this bias could allow more sensitive tests for dementia to be developed. I aimed to test the theory that a particular cortical region, the right hemisphere intraparietal sulcus, is dominant in orienting visuospatial attention, and could therefore be responsible for the leftward Light Source Bias in young people. Using transcranial magnetic stimulation to disrupt functioning in this region. I expected to see a reduced leftward bias after stimulation; however, no statistically significant results were observed. Though this is not the result we had hoped for, the experimental process revealed a number of theoretical and methodological considerations that will be important to consider for future work in this area.
Receiving a grant from the James Pantyfedwen Foundation enabled this work to be carried out, and my funded PhD will continue this research. As I would have been unable to fund this course myself, I would like to extend my sincere thanks and gratitude to you. Diolch yn fawr iawn.