“We can feel more than the eye can see”
(Serge Benhayon – Esoteric & Exoteric Philosophy)
Blindsight is a phenomenon where a person who is blind or partially blind can unconsciously ‘see’ in their blind visual field, even though they have no awareness of this ‘seeing’.
A person with blindsight has cortical blindness, i.e. they have healthy eyes but a damaged or removed visual cortex. They receive light through their eyes but it is not ‘seen’ and they are seldom aware of it. Destruction of the visual cortex and subsequent blindness can occur through strokes, tumours, disease, trauma or accident.
Neuropsychologists and neuroscientists have extensively studied people with blindsight to better understand what they can and cannot perceive. This is done by presenting objects or images into their blind field – the area where they have absolutely no ability to ‘see’ anything – and comparing their response to when the same is presented in their sighted field. For example, comparing how they reach out and grasp an object placed in either field (interestingly the results show that a person can accurately reach out and grasp an object that they have no awareness of seeing).
In one research experiment, pictures of facial or bodily expressions were presented to either the sighted or blind visual field of two patients with blindsight. The response of their muscles and pupil reactions were measured, and it was found that:
- The patients could sense the emotion presented in their blind field and even started to unconsciously mimic the expressions (i.e. the corners of the mouth turned up very slightly in response to seeing a smiling face).
- They showed physiological signs of stress when they ‘saw’ (in their blind field) a picture of a frightened face.
- Most interestingly, exposure to ‘unseen’ expressions evoked faster reaction (in the body and face) compared with seen stimuli, indicating that facial or bodily expressions in others are felt before they are consciously seen.
Emotional communication does not therefore require cortical vision (actual seeing) and can occur without any conscious experience.
In another study a patient was presented with fearful bodily expressions in either their blind field, sighted field or both fields at the same time. Neuroimaging and pupil reactions were used to measure their response.
- Pupil dilation (indicating a ‘fight or flight’ nervous system response) increased more when fearful bodies were presented to either the sighted, blind or both fields. However the dilation was bigger when the fearful body was presented in the blind field than when it was consciously seen.
- Neuroimaging showed that fearful bodies activated the same areas in the brain when consciously perceived as well as non-consciously perceived in the blind field. However, the response was faster when presented to the blind field.
So brain mapping shows that the body senses and responds spontaneously to unconscious perceptions before the brain can see them. The body actually clocks and anticipates (feels) the significance of the ‘unseen’ stimulus and prepares for it before it is seen. By feeling what is coming our way we can then direct our visual awareness to it for subsequent action or response. We can use our vision to see what we have already felt.
References:
- de Gelder B. Vroomen J. Pourtois G. Weiskrantz L. Non-conscious recognition of affect in the absence of striate cortex. Neuroreport 1999;10(18):3759-63.
- Tamietto M. de Gelder B. Neural bases of the non-conscious perception of emotional signals. Nature Reviews 2010;11:697-709.
- Tamietto M. Castelli L. Vighetti S. Perozzo P. Geminiani G. Weiskrantz L. de Gelder B. Unseen facial and bodily expressions trigger fast emotional reactions. Proceedings of the National Academy of Sciences 2009;106(42):17661-17666.
- Tamietto M. Cauda F. Celeghin A. Diano M. Costa T. Cossa FM. Sacco K. Duca S. Geminiani GC. de Gelder B. Once you feel it, you see it: Insula and sensory-motor contribution to visual awareness for fearful bodies in parietal neglect. Cortex 2015;62:56-72.
