It says :<p>&quot;The gratiﬁcation resulting from each jerk depends only on the physical andgeometric parameters of the problem (shaft girth, hand size). For instance,a 20 year old man who hasn’t been stimulated in a week’s time receives the same gratiﬁcation from a jerk action as would a freshly stimulated 80year-old-man, provided the geometric parameters are identical&quot;<p>This is questionable, a 20 year old man probably receives more pleasure from an act of masturbation compared to an 80 year old man, because statistically a 20 year old man&#x27;s penis will be much more sensitive compared to an 80 year old man&#x27;s --- the authors should have factored that into their calculations