Barking up the wrong tree

I've just found a remarkable 1963 study [pdf] from the Archives of Opthalmology in which 24 blind participants took LSD to see if they could experience visual hallucinations.

It turns out, they can, although this seems largely to be the case in blind people who had several years of sight to begin with but who later lost their vision.

Those blind from a very early age (younger than two years-old) did not report visual hallucinations, probably because they never had enough visual experience to shape a fully-functioning visual system when their brain was still developing.