Höfundur bókarinnar Physiology of Behavior, Neil R. Carlson, er stórkostlegur. Þó svo að efnið sem hann er að fjalla um hafi alla burði til að vera þurrt og leiðinlegt, þá er hann duglegur að krydda textann með skemmtilegum útskýringum og dæmum. Í undirkaflanum Hormonal Control of Sexual Behavior má fræðast um sáðlát karldýra og hvíldartímann sem þarf að líða þangað til þeir eru tilbúnir að nýju. Í ljós hefur komið að hjá sumum spendýrum hverfur þessi hvíldarþörf hjá karldýri, örmagna eftir nokkur sáðlát með sama kvendýrinu, sem dögg fyrir sólu um leið og nýtt kvendýr kemur til sögunnar. Þessi eiginleiki er talinn nauðsynlegur hjá tegundum þar sem eitt karldýr þarf að frjóvga mörg kvendýr. Hér bætir höfundurinn við tveimur sögum:

In one of the most unusual studies I have read about, Beamer, Bermant, and Clegg (1969) tested the ability of a ram (male sheep) to recognize ewes with wich he had mated. A ram that is given a new ewe each time will quickly begin copulating and will ejaculate within 2 minutes. (In one study, a ram kept up this performance with twelve ewes. The experimenters finally got tired of shuffling sheep around; the ram was still ready to go.) Beamer and his colleagues tried to fool rams by putting trench coats and Halloween face masks on females with wich the rams had mated. (No, I´m not making this up.) The males were not fooled by the disguise; they apparently recognized their former partners by their odor and were no longer interested in them.
The rejuvenating effect of a new female, also seen in roosters, is usually called the Coolidge effect. The following story is reputed to be true, but I cannot vouch for that fact. (If it is not true, it ought to be.) The former U.S. president Calvin Coolidge and his wife were touring a farm, when Mrs. Coolidge asked the farmer whether the continuous and vigorous sexual activity among the flock of hens was the work of just one rooster. The reply was yes. She smiled and said, "You might point that out to Mr. Coolidge." The president looked thoughtfully at the birds and then asked the farmer whether a different hen was involved each time. The answer, again, was yes. "You might point that out to Mrs. Coolidge," he said.