Science: Light of Love?

June, traditional month for weddings, is also the month with the year’s longest days. Professor Thomas Hume Bissonnette, of Trinity College at Hartford, Conn., thinks this no coincidence but scientific cause & effect.Last week he told of some experiments on animals which seem to prove that light (not temperature, as long supposed) is the prime external factor controlling love and mating.

Pink-cheeked, twinkling Biologist Bissonnette is one of the world’s leading authorities on photoperiodicity — the study of the effect of light on animals’ and plants’ seasonal cycles. The earliestapplication of this science, so far as he knows, was by Spanish peasants who in 1602 used torchlight to stimulate hens’ egg-laying. Poultrymen used to believe that the reason artificial light improved hens’ production was that it made them eat and exercise more. But Professor Bissonnette showed that the light itself stimulates laying.

He pursued his researches further with pheasants, starlings, weasels, goats, mink and raccoons. By regulating the amount of light they got each day, he made raccoons bear two litters a year instead of one, made goats breed in summer instead of winter, induced pheasants, which normally lay their eggs in April, to lay them on the snow in midwinter. By the same means, he fooled minks into growing a rich brown winter pelt in summer and shedding in winter, made weasels change their coats from brown to white and back to brown again most unseasonably.

Duration, Not Intensity. Professor Bissonnette concludes that all this proves that the pituitary gland, which lies at the base of the brain, is affected by light transmitted by the optic nerve. He points out that if an animal’s optic stalk (connecting the eye and the brain) is cut, the animal will change its breeding season. He also found that the intensity of light seems to make little difference; what counts is its duration. The pituitary gland apparently is also stimulated by color: red light, for example, moves starlings to mate more than any other hue.

Biologist Bissonnette concedes that light does not affect all animals alike, and that in the tropics, where the length of days varies little with the seasons, mating animals must be affected by something else. But he would like to know, if his theory is not correct, why swallows always arrive at Capistrano on the same day of the year, regardless of temperature.

Photoperiodicity, still a brand-new theory, has little data as yet on the effect of light on man, but Professor Bissonnette notes that the long Arctic night seems to dull the mating urge among Eskimos. The professor hopes some day to investigate this report ; the AmericanPhilosophical Society and other scientific groups are already subsidizing his animal investigations.