Blindsight

How Do Blindsighted Individuals Discriminate Visual Stimuli?

The phenomenon of blindsight may be described as a “feeling or impression of something not seen.” You can rig up visual displays in which people reliably discriminate unseen stimuli, essentially a form of subliminal perception.

The difference is that with subliminal perception Opens in new window, there is normal visual experience behind which covert information sneaks in.

Peripheral vision Opens in new window is a similarly analogous case, although here we expect little or no consciousness, whereas blindsight is pretty clearly vision without expected visual consciousness.

To put in a layman’s terms, what we see with our eyes goes through two pathways to our brain.

1. One is a where pathway that determines that something is there, where it is, and how it relates to us spatially. It’s a primitive pathway.
2. The second is the what pathway, which then tells us what the object is and how we should react to it.

That first, primitive pathway sometimes still works in blind people. A blindsighted individual may sense something is there, even if s/he can’t see it.

In blindsight phenomenon, the normally used visual cortices and pathways do not process visual information and yet over time, persons to respond to visual sensation.

Blindsight has been demonstrated in monkeys where the entire primary visual cortex has been removed experimentally.

• Blindsighted individuals learn over time to orient toward light,
• identify the presence and absence of stimuli,
• discriminate shapes and edges, and
• can avoid obstacles while walking or running.

Particularly in the case of avoiding obstacles, one sees clearly the execution of sound judgment without apparent insight Opens in new window.

It appears that blindsight, or unconscious vision, is made possible as the brain recruits intact pathways of the primitive subcortical mammalian visual pathway that are not normally used in humans and monkeys.

These pathways are also not routed through sections of the brain that produce awareness that can be verbalized. While persons improve their blindsight abilities with training, they never gain verbal consciousness of this.

While blindsight improves, no research that we are aware of has demonstrated that humans have utilized metacognitive processes Opens in new window to evaluate and select this new modality in decision making or concept formation Opens in new window. Blindsighted individuals remain unaware of their improved “visual skills”.

Thus, in the phenomenon of blindsight we see judgment (e.g., to act, to avoid obstacles, to determine the presence or absence of an object) occurring without insight Opens in new window and knowledge that comes to exist presumably independently of the auspices of one’s metacognition Opens in new window. While their abilities improve, they remain unaware of this.

What appears to have parsed these concepts is consciousness Opens in new window; in particular, verbal consciousness. For it remains difficult to conceive of an individual who can run and actively avoid obstacles without truly being aware of them at some level.

Rather, it seems that the various concepts such as knowledge, insight, awareness, judgment, and understanding are present and operative but not with their usual verbal overlays.

This conceptualization brings blindsight closer to a pure but limited stimulus-response (S–R) model Opens in new window.

S–R models are particularly good at explaining behavior emitted without apparent awareness (Brunner, 1992; Greenwald, 1992; Kilstrohm, 1987).

Examples of such behaviors include automatic behaviors, where verbal stimuli have dropped out of response chains; not being aware of shifting gears while driving, subtle mood changes following changes in weather and lighting; particular food cravings; or possibly certain compulsive behaviors.