Slight aside... We've known for hundreds of years that neutering animals results in a retention of juvenile behaviors. Geldings are more docile than stallions, largely because they retain the behavioral profile of a foal. They attain generally adult size and proportions, but they don't develop adult behaviors. The same is true for domestic dogs and cats. Sterilized dogs retain a lot of puppy-like behaviors, sterilized cats retain kitten-like behaviors. Steers don't act like bulls. There's an entire set of cognitive behaviors that develop during sexual maturation in mammals. Why we would imagine that humans would be different is a mystery to me.
Also... in male cats, neutering reduces the development of adult male facial conformation. Toms actually look different from neutered males. Body shape, particularly abdominal, is different for spayed females and intact queens.