Interindividual differences in perception

Interindividual differences in perception describes the effect that differences in brain structure or factors such as culture, upbringing and environment have on the perception of humans. Interindividual (differing from person to person) variability is usually regarded as a source of noise for research. However, in recent years, it has become an interesting source to study sensory mechanisms and understand human behavior. With the help of modern neuroimaging methods such as fMRI and EEG, individual differences in perception could be related to the underlying brain mechanisms. This has helped to explain differences in behavior and cognition across the population. Common methods include studying the perception of illusions, as they can effectively demonstrate how different aspects such as culture, genetics and the environment can influence human behavior.

A motion quartet is a bistable stimulus - it consists of two dots that change their position from frame to frame. This position change can either be interpreted as horizontal or vertical movement by viewers, and this experience can switch during viewing between interpretations. Depending on the aspect ratio of the two dots' positions, one or the other state is perceived longer or more often. At an aspect ratio of one, the illusion is biased towards the vertical perception. The reason for this might be the way the human brain processes the signals from both eyes in the visual system. The right half of an eye's field of view is processed by the left hemisphere, and the left half by the right hemisphere. A stimulus moving vertically only involves one field of view and so one hemisphere, while a stimulus moving vertically from one field of view to the other involves both hemispheres, and requires communication between them. The delay caused by this additional signalling might be the cause for the bias. There are also individual differences in the way the motion quartet is perceived: Some people require a different aspect ratio to perceive both axes of movement than others. A study using diffusion tensor imaging further showed differences in the structure of the corpus callosum, the primary connection between the two hemispheres, might be the origin of these differences.

...
Wikipedia