Conclusion

So what relevance does change blindness have? Is it just another example of the quirky sorts of visual illusions which psychologists love to collect? After all, it's not often our vision is interrupted by 100 millisecond duration grey rectangles covering our visual field.

In actuality, however, our vision is interrupted in exactly such a way but our perceptual system does a lot of work to hide this from us. The most common behaviour performed by a human being is the saccade, or rapid eye movement. During each of those movements, our vision is degraded markedly, due to the eyes rotating at hundreds of degrees per second- too rapidly for the retina to integrate useful information. We execute 100 000 to 200 000 saccades every waking day, each lasting roughly 50 - 100 milliseconds. Add that up: we spend 10-20% of our waking lives functionally blind. That this is something of which we are not generally aware is perhaps the greatest illusion of all time, and illustrates the brain’s immense capacity for self-delusion.

In our lab, we use this phenomenon to investigate motor learning. In essence, we shift a visual target while a person makes an eye movement toward it. As a result the eyes land in the wrong place. Occuring during a saccade, the target shift is not consciously detected. The error in eye position is, however, able to be detected and corrected by the motor system. This allows us to assess a form of learning (saccadic adaptation) that occurs at a subconscious level. Some of our papers on this topic are available here and other studies are ongoing.

This demonstration was created by Michael MacAskill. A set of larger images are available which are more suited for PowerPoint or Keynote presentations- contact me if you would like them.