In the book `` Human Sexuality : Diversity in Contemporary America '' , by Strong , Devault and Sayad , the authors point out , `` A baby boy may laugh in his crib while playing with his erect penis '' .
In the book `` Human Sexuality : Diversity in Contemporary America '' , by Strong , Devault and Sayad , the authors point out , `` A baby boy may laugh in his crib while playing with his erect penis ( although he does not ejaculate ) .