Most of the 20th century was a kind of dark ages, for all ideas about inborn human nature, as I suggested in a recent blog. One of the fascinating things about such dark periods, however, is that the seeds of their destruction are often growing merrily in that darkness. Especially in the later part of the century, nurture had all the publicity, all the support of “public” experts, and the often-happy, but sometimes-grudging support of parents.
Under the radar, very different forces were sprouting–in isolation at first, but gradually in greater cross confirmation. Animal research was one of these forces. On the one hand, behavioral psychologists were demonstrating that animals could be taught all sorts of specific behaviors, and claiming that there were no innate behavior patterns; however, other researchers in biology, animal science and experimental psychology were quietly building up evidence to the contrary.
Animal instincts? In the very early part of the century virtually everyone took these for granted, but by 1930-40, research in this area virtually disappeared. By the 1950s the idea had quietly returned. A little later, the ethologist, Konrad Lorenz became famous for his studies on geese who learned in 24 hours of life to follow the first figure they saw. Though normally this was the gosling’s mom, he demonstrated to great public delight that the goslings would also learn to follow him.
Another widely known group of studies were those done by the psychologist Harry Harlow, on monkey infants. Deprived of the mother at birth and given two choices of mother substitute (a comfy cloth mother that offered no food, and a cold wire mom with a bottle available, they quickly learned to grab a little milk from wire mom and then run back to comfy cloth mom. This dealt a huge blow to the Pavlovian/Skinnerian idea that all animal behavior was produced by simple rewards like food. There really was no way to make this fit the conditioned learning model. By the late 1960s these and many other studies converged, and instinct theory came roaring back.
Meanwhile, other research had begun to look at differences within species and sub-species. Rather than asking whether pigeons could be taught to peck at a red light with food reward, the more interesting question became whether all pigeons (rats, mice, etc.) would do this equally well. Animal models of fearfulness became especially popular, and the open field test was born for rats and mice. Neither species cares for bright light, being nocturnal, nor for wide open areas with nowhere to hide. For rats an experimental open field was a box about 3ft. by 3ft. with walls about a foot high and glossy white paint. Anxiety was measured in rates of freezing in one spot, and urinating, and defecating. It soon became clear that different strains of rat within the species showed very different fear patterns. It was not far from that to demonstrating that deliberate breeding of fearful with fearful and fearless (relatively) with fearless could produce groups that permanently differed from one another on open field anxiety. Much later it could be shown that the fearful groups had larger amounts of the brain transmitter norepinephrine than the calmer groups, as well as other differences in transmitters, stress hormones, and brain activity in specific areas. Today, many species, including the tireless rat, are used in testing new anti-anxiety medicines and for this the open field remains a staple design.
How about our friend, the dog? Any animal breeder, and any good rancher would have said without need of laboratory experiments, that animal temperament is innate and can be bred for. We are all aware of the huge range of sizes, colors, coats and body builds in the well-bred dog, and most of us have pretty strong opinions on breeds that are aggressive, calm, nervous, independent, attached, and so forth. In terms of practical behaviors, as one writer said, “Sheepdogs herd, retrievers retrieve, trackers track, and pointers point, with minimal training.” (Plomin et al., Behavioral Genetics, 1997.)
However, researchers have taken the trouble to demonstrate canine temperament differences in controlled conditions. One study reported in 1965 studied fox terriers, cocker spaniels, basenjis shetland sheepdogs and beagles over a period of 20 years (selected partly for similarity in size). Terriers were the most aggressive and spaniels the least aggressive. Sheepdogs were the most trainable for practical tasks. Most timid were the basinjis, terriers and sheepdogs. Other research on larger breeds has shown the German Shepherd to be the most fearful and the lab the least fearful.
Also ongoing in the later 20th century were field studies of many primate species.. Here it was possible to look at social and other behaviors closer to our own. It is a fact that the commonest human stressors are all social in one way or another, (loss of a loved one, marital breakup, and serious interpersonal conflict). This is equally true for monkeys and other primates. If anything, infant primates may be more vulnerable to these stressors than human children, since loss of the mother or other caregiver often leads to death, even in monkeys who are old enough to obtain and eat solid foods. Particularly interesting then are findings about three closely related strains of macaque monkeys. The rhesus monkey is the best known of these. The other two groups are the crabeater and the bonnet. As Kagan reports in Galen’s Prophecy, the rhesus is the most aggressive (and physically biggest) and the least disturbed under stressful experimental conditions. The poor little crabeaters were the most stressed out with elevated heart rates and elevated output of stress hormones, and the bonnets were in between in their stress response, and seemed to have a generally passive and avoidant approach. Not only are these strains very distinctively different in these areas, they are different even though closely related.
These and many, many other animal studies,both in nature and in laboratory experiment seemed to say, even in the century of denial, that our animal ancestors and cousins, near and distant, did not and do not come into this world as a blank slate.
More to come!
•Plomin et al. Behavioral Genetics