Didn't perform experiments, just studies of emotional development.

He believed that personality development takes place through a series of identity crises. I agree with this.
He discovered his theory by looking at his own life and personal struggles. For example, thinking his strop father was his real father.

He specifically studied the phase of the identity crisis throughout a person's life and what exactly makes them question who they are/going to be.

In addition the Harvard, he also taught at Yale and U.C. Berkeley for many years.