Re: when did scientists realize that the brain, not the heart, was used for thought

Caroline,

It's never easy to pin down when an idea started, or when it took hold.

According to the first chapter of Stanley Finger's "Origins of Neuroscience" (Oxford University Press, 1994), "the Brain in Antiquity," the first Greeks on record as proposing the role of the brain were Alcmaeon (circa the fifth century BC) and Anaxagoras (500-428 BC). Hippocrates (460-370 BC) -- yes, that Hippocrates -- spelled out the role of the brain in writings on seizure disorders.

However, even Aristotle (384-322 BC) stuck with the idea that the heart was where the mind lived.

Galen (130-200 AD) had the middle idea that "vital spirits" produced by the heart were translated into "animal spirits" by the brain. He recognized that damage to the brain could affect the mind, but thought it was because ventricles of the brain were damaged, allowing the "spirits" to leak out.

Serious attempts to tie the brain's anatomy to mental functions don't show up until the Renaissance.

Finger's chapter does list evidence that prehistoric civilizations performed some sort of "trepanation" -- deliberately putting holes in the skull -- but there's no way to know whether the trepanation was done for medical or metaphysical reasons.