You already learned about blindsight and the incredible ability to process visual information even without consciously seeing it. Now let’s learn about some of the research done to learn more about blindsight.

Laboratory Research on Unconscious Visual Processing

Dr. Tony Ro is a professor of psychology at the City University of New York. He started studying the connection between consciousness and brain processing more than 20 years ago, and he was one of the earliest researchers to apply TMS technology to the study of visual perception.

In one study, Dr. Ro and graduate students Jennifer Boyer and Stephenie Harrison used TMS technology to see if sighted people could process features of visual stimuli without conscious awareness of those stimuli. In other words, they wanted to know if they could create temporary blindsight in sighted subjects in a laboratory.

Remember that blindsight involves unconscious awareness of “features” of objects and events, such as the shape of an object or the direction of its movement. This study focused on two visual features: orientation and color. You and I see orientation (horizontal or vertical) or color (red or green) as part of the experience of some object. A line is horizontal. A box is red. For a person with blindsight, “horizontal” is experienced without any shape associated with it. “Red” is experienced without becoming aware of the thing that is red. This is the blindsight condition that Dr. Ro and his colleagues wanted to reproduce in the laboratory with the help of volunteer subjects.

Let’s walk through the experiment to understand how it was designed and conducted.

Experiment 1: Unconscious Detection of Orientation

SETUP: The TMS wand was precisely adjusted so the TMS pulse was aimed at the back of the brain (primary visual cortex in the occipital lobes) affecting a very small area of the visual field. For example, imagine the gray box below is a computer screen. The plus sign in the middle is a fixation point. You (the participant in the study) are asked to fixate your eyes on this plus sign for the duration of each trial. While you focus on the plus sign, the TMS pulse is then adjusted to your individual brain so that the area of your visual field shown as the blue circle (used here only for explanation purposes) is momentarily rendered “blind” when the pulse is active. This is a painstaking process that involves fine calibration of the wand based on feedback from the participant about what they can see when different targets are shown on the screen.

TESTING: In one of Dr. Ro’s experiments, participants had to guess the orientation of a line (either horizontal or vertical), sometimes when they were temporarily blinded (in a tiny area of the visual cortex) by a TMS pulse. The study consisted of a series of trials. On each trial, either a horizontal or a vertical line was flashed for a fraction of a second on the computer screen in front of the participant. On some of these trials, a TMS pulse disrupted the neurons in the visual cortex. On other trials, there was no TMS pulse. The no-pulse trials served as a kind of control condition.

Click on the slideshow below to see the steps in the vertical line condition. You can use the arrows at the bottom to navigate through the slides.

Applications of Blindsight

If we process and react to more visual information than we are consciously aware of, then it is possible something similar is occurring with our other senses (touch, taste, smell, hearing).

Let’s try some exercises together to explore similar subconscious reactions in everyday life.