This is Australian law, not US law, but Inchoate found quite an amusing passage in a trademark case involving magazines aimed at young girls between 6-13 years ("tweens"). (Girl Power?). From the decision:

I am not satisfied that Mr Lindstrom’s evidence in this case can be accepted as expert evidence in relation to the perception of tween girls. It is not based on any identified or specific empiric examinations referred to by him in his material. He claims to be a leading expert with many years of experience, however, the prime nature of this experience is unclear.