A college psychology class was studing human reaction to sexual stimulus and of special interest was the frequency of amorous relations.
''How many students here,'' said the professor, ''engage more than once a week?'' Five people raised their hands.
''And how many engage once a week?''
Ten hands went up.
''How many twice a month?''
Eight hands went up.
''Once a month?''
Four hands were raised.
''And how may once a year?''
A little guy in the back waved his hand frantically and giggled hysterically.

''If you engage only once a year,'' said the professor, ''I don't see what you're so overjoyed about.''
Flush with excitement, the little guy said, ''Yeah, but tonight's the night!''