I want to know why we cannot use the former. I have been told that only the latter is correct but I want a more definite explanation of this. Why is it that we can say "the human mind", "the human body" but not "the human psychology"?
You can, as long as you're talking about a specific human psychology, for example
"The human psychology behind Facebook Success is not easy to explain"
You could argue you're talking about human psychology in particular as opposed to psychology in general, but by definition, there is no psychology other than human psychology; thus, by saying human psychology you're effectively talking about psychology in a general way.
This is easier to see if we take other uncountable nouns, for example: you can say, "the tea in my cup is cold", but you can't say "I like the tea"; the correct way to say that, as you're talking about tea in general, is "I like tea". Same goes for other uncountable nouns like water, sand, soil, sugar, etc.