Consciousness: Apply It

  • Describe consciousness
  • Understand blindsight

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

Theme A: Psychological science relies on empirical evidence and adapts as new data develop.
Figure 1. Step through this research on blindsight to learn more about how empirical evidence is collected.

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.

Image of a person with a TMS wand held over the head. To the right of that, there is a cross and a white circle with a blue outline. This represents how that circle would temporarily disappear for someone during the TMS stimulation.
Figure 4. Researchers adjusted the TMS wand until the circle would temporarily disappear from a person’s visual field.

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.

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.
EXPERIMENTAL RESULTS:  By chance, if you have to choose between two equally likely options (horizontal or vertical), you would be correct about 50% of the time.On the trials when the subjects reported that they did not “see” anything at all, they correctly guessed the orientation of the line 75% of the time, performance that is significantly better than chance. There was also a strong positive correlation (r = +0.93) between accuracy and confidence: the more confident the subject in their guess, the more likely it was that the guess was correct. Keep in mind that, in all of these cases, the subjects started by saying that they saw nothing. That was about 60% of the trials. On the other 40% of trials, the subjects reported seeing something, even if it was a slight blur, and these trials did not count. Not surprisingly, accuracy was near perfect when subjects were conscious of seeing the bar and its orientation.A second study using the color of a circle rather than the orientation of a bar was reported in the same paper. Otherwise, the procedures were the same as in the first experiment and the results were consistent with the results for the bar orientation experiment.
Here is a video about a similar experiment conducted by Dr. Ro and his colleagues. The experiment in the video involves detecting yet another feature of objects: their shape. The basic procedures and results are similar to the ones you have just read.
You can view the transcript for “Seeing Beyond the Visual Cortex – Science Nation” here (opens in new window).

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.

Type your ideas into the open boxes and compare your responses with the sample answers shown below.1. Can you imagine a scenario in which your brain might be processing and reacting to sensory (touch) information that you are not consciously aware of? 

2. Can you think of a scenario in which your brain might be processing and reacting to gustatory (taste) information you are not consciously aware of?

3. Can you imagine a scenario in which your brain might be processing and reacting to olfactory (smell) information that you are not consciously aware of?

4. Can you think of a scenario in which your brain might be processing and reacting to auditory (sound) information that you are not consciously aware of?