If you are a parent you can identify with the following definition.
An attack of temporary imbecility suffered by a two year old child normally regarded as a genius, and occurring at such a time as to make her mother look like even more of an imbecile than she is. The two year old, when alone with the mother, may be able to read newspapers, recite Hamlet, and figure Dow-Jones averages in her head, but upon the arrival of company and being asked by her mother to show off her genius, she will develop a vacant stare and a slack mouth and be unable to remember her own name.
B.M. Atkinson Jr.