In 1935, neurophysiologist John Farquhar Fulton presented some shocking new research.
After removing the frontal lobes of two chimps, he found they no longer experienced frustration or anxiety.
As his research associate noted, it was as if they'd joined a "happiness cult." Admittedly, the surgery had cost Fulton's chimps some cognitive functions.
But to Portuguese neurologist Egas Moniz, this was a small sacrifice for what seemed to be eternal happiness.
Moniz believed that replicating this procedure in humans could cure mental illness.
And it was this therapeutic intention that led to one of the most controversial and destructive medical treatments of the 20th century: the lobotomy.
Today, we know mental illness comes in many forms and emerges for many reasons.
But in the early 20th century, these complex conditions weren't clearly delineated, and researchers had various theories about their origins.
Moniz believed the symptoms of what we now call depression, OCD, and bipolar disorder stemmed from negative ideas getting fixed in the neural fibers which connect different parts of the brain.
Specifically, the thalamus and frontal lobes, which regulate emotion and sensation.
