How would the blind experience a hallucinogen like LSD?

Question

I have heard that LSD allows you to see ridiculous things. But they are things that you have seen, or can imagine to see. If you've never seen before (like a blind person), what effect will LSD have on you? Articles on google do not go into the specifics of the brain functionality when the drug is taken. I'm looking for a more detailed explanation

Answer 1

Short answer
Based on a dated and small study, early-blind individuals do not experience drug-induced hallucinations, while the late-blind can, but not necessarily do so.

Background
Krill et al. (1963) investigated the effects of LSD on totally blind people (i.e., no residual vision) and they report visual hallucinations in 13 out of 24 subjects. This study shortly reviews three other studies in this field (LSD and mescalin administered to blind people) and the consensus the authors reach is that blind folks do experience visual hallucinations.

However, as @JoeBathelt very rightfully notes, it is important to acknowledge the difference between congenitally blind and late blind people that lost vision later in life. Late-blind individuals often experience visual imagery, while congenitally blind do not and cannot. In the Krill et al. study linked, they included four congenitally blind subjects. The remainder were acquired blind that had lost their eye sight later in life. The congenitally blind group had lost their vision at, or before the age of two (which I would call early blind, but that's debatable). None of these 4 subjects experienced hallucinations. Given that half of their study group experienced hallucinations, one would expect two of these four to have experienced hallucinations. Although the congenitally (i.e., early-blind) group was small, it leads me hence to believe that prior visual experience at least early in life is a prerequisite for visual hallucinations to occur. However, not many studies have been published on the topic and I am most curious to see more answers to this most interesting question.

<sub>Reference
- Krill et al., Arch Ophthal (1963); 6: 180-5</sub>

Answer 2

I'm not sure about any reliable research on hallucinations in blind people per se. However, there is a large body of literature on visual imagery in congenitally blind groups. This is assuming that hallucinations are based on typical representations, but are usually held in check through inhibition.

Research conducted by Pring et al. found that congenitally blind people experienced non-visual imagery in a memory recall task, but the imagery was less vivid in comparison to typically-sighted controls (Goddard & Pring, 2001). A review by Cattaneo and colleagues also indicated that imagery does exist in congenitally blind people, but that it may rely more on verbal or haptic representations.

Extrapolating from this research, one would assume that congenitally blind individuals experience hallucinations that are based on non-visual experiences and that these may be less vivid compared to visual hallucinations in sighted people.