This demonstration concerns hemispheric specialization. The basic hemispheric specialization theory is that the brain is divided into two separate hemispheres -- right and left. The hemispheres cannot communicate except through a structure called the corpus callosum. When stimuli are presented to the right visual field, because of the way the neural pathways from eye to brain are configured, this right visual field is sent directly to the left hemisphere and only the left hemisphere. The reverse is true for the left visual field.

Hemispheric specialization theory says that certain tasks can be process only by the right hemisphere or only by the left hemisphere (but not by both hemispheres). If the information that arrives in a hemisphere can be processed by that hemisphere, then the response time will be shorter and the processing will be more accurate than if the information cannot be processed by that hemisphere and must be sent, via the corpus callosum, to the other hemisphere.

Based on these accuracy and response time measures, it has been found that the left hemisphere appears to be specialized for verbal tasks while the right hemisphere is specialized for spatial tasks.

Since not everyone is specialized is the standard way, verbal or spatial tasks can often be used to ascertain the exact nature of a persons specialization.

In this experiment, you be deciding if letters flashed to your right and left visual fields are uppercase or lowercase. The experiment begins with the following screen (except there will be no red circle).

When you slide the mouse pointer over the small square (that has been circled in red for these instructions), numbers will appear in the two boxes to the left and right of the small square. The number will count from 1 to 5.

As soon as 5 is reached, a letter will be flashed in either the far left box (that has now been circled in red for these instructions) OR the far right box (that has now been circled in purple for these instructions).

As fast as you can, you respond as to whether the flashed letter was uppercase or lowercase by sliding your mouse pointer over the word UPPERCASE or LOWERCASE. This action records your response time.

You can now slide the mouse pointer over the small square again and the count (1 to 5) will start for your next trial. The trial number is indicated at the top of the screen in the box next your the words TRIAL #. There will be a total of 20 trials.

It is difficult to do good research on hemispheric specialization because one must maintain visual fixation on a center point while the information is flashed to the left or right of this fixation point. The way the eyes are designed, anything to the left of where a person is visually fixated (called the Left Visual Field or LVF) goes only to the right hemisphere of the brain. Anything to the right of where a person is visually fixated (called the Right Visual Field or RVF) goes only to the left hemisphere of the brain.

When a hemisphere receives information from the visual field, if it can process that information, it does so immediately. If it cannot process the information, it send the information to the other hemisphere so that the other hemisphere can process the information.

By measuring how fast information is processed, we can tell if the hemisphere, where the information was sent, processes that information (fast response time) or has to send the information to the other hemisphere to be processed (slower response time).

This response time comparison can only be made accurately if a person is truly fixated at a center point and doesn't move his or her eyes to the letter location when the letter appears.

In doing this experiment, when you move the mouse pointer over the small square, leave it on the small square and try to keep yours eyes fixated on the mouse pointer. If you are successful, when the letter flashes, it should be blurry rather than clear. You should have an impression of whether the letter was uppercase or lowercase, and that is all you want. Respond based on your impression. If a letter appears clear to you, then you are probably not fixated on a center point.

At the end of 20 trials, a new window will open that shows your results. Twenty trials is probably too few to really get an accurate picture of your hemispheric specializatation. There is a 100 trial version you can try. However, it will be difficult to keep your fixation and concentration thoughout so many trials.

When you have read and understood these instructions, Please click on the word START below, to begin.