"Gentling" is a process involving trans-generational change. The term refers to the gentle handling of rats by their human caretakers. The gentle handling appears to cause behavior changes in rats that are passed on to other generations of rats. The phenomenon was discovered inadvertently by animal behaviorists doing experiments with rats. They observed:
When female rats are handled gently during their infancy and early life, they appear at maturity less emotional, more ready to leave their cages, and less fearful of strange stimuli than do other rats. In fact, the animal is able to respond more effectively when confronted with normal situations; in other words, its emotional response to novel but normal stimuli is not as intense as it is in rats raised in the usual manner. When such rats become mothers, the body weight and readiness to explore of their young are different from those of standard controlled groups. These effects appear to be mediated through both the prenatal mother-fetus and the postnatal mother-infant relationship. Not only are the young themselves of a different temperament as the result of the early experiences of their gentled mothers, but, when these young bear babies their patterns of mothering are also different from what they would have been normally. Because the effect of the gentling that their mothers received becomes apparent in their grandchildren, it has been called "the grandmother effect." (Encyclopedia Britannica, 1979)
The phenomenon of "gentling" appears to be distinct from that of "imprinting" (which can also involve the interaction between humans and other animals). Imprinting is a special form of learning, which also occurs during a critical early stage in life, in which the young within a species instinctively recognize and follow a "mother figure." While the "mother figure" is usually their biological mother, it can also be other members of their species, or in some cases a member of another species all together. Such imprints, however, are extinguished with the death of the individual, and not transferred naturally to their children. The offspring of a duckling that is imprinted to a human will not be anymore predisposed to imprint to humans than any other duckling. Imprints must be re-established through the life experiences of each animal. The affects of gentling, on the other hand, appears to be passed on to following generations through some type of biological mechanism.
Gentling also differs from imprinting in that it requires inter-species interaction (i.e., the baby rat must be "gentled" by a human rather than another rat). Imprints may be established with respect to other species (a duckling can become "imprinted" to a person), but this is the exception to the rule, and is certainly not a requirement of imprinting. Gentling, on the other hand, appears to actually require the initial involvement of the human.
The positive affects of the gentle handling of animals by humans have also been observed in other experiments as well. In a study done on rabbits, "gentling" was found to have a remarkable impact on the health of the animals. Six groups of rabbits in different locations were being fed extremely high fat diets to see if they would develop heart disease. As the experiment progressed, five of the six groups were responding as expected; becoming ill and dying. But one group remained quite healthy. At first researchers thought that the group must not have been receiving the appropriate high fat diet. But, when they checked, they discovered the rabbits had been fed exactly as the same as the other groups. The researchers then postulated that the rabbits must have been allowed more exercise. But this was also shown to not be the case. The only difference, in fact, that they were able to find was that the individual responsible for feeding the rabbits was fond of them, and would pick them up and pet them gently at feeding time.
Similar positive effects have been found to result from the gentle touching or "stimulation" of premature babies. The body weights and survival rates of premature children who are touched gently is significantly higher than those who are isolated. (It is also interesting to note that the nurses who were instructed to touch the babies gently reported that it changed their own feelings toward the babies, creating a sense of relationship with the infants.)
While no data currently exists to indicate whether or not there is a trans-generational "grandmother effect" in either of these other instances of gentling, there is data which demonstrates that the opposite of gentling, "isolation," produces detrimental effects which are not transferred to other generations.
It has been widely reported, for example, that baby monkeys who are isolated from contact with their mothers and other monkeys suffer enormous social-sexual dysfunctions. The isolation of a monkey infant for nine to twelve months after birth permanently destroys sociability with age mates as well as all forms of sexuality and social communication. Unlike the phenomenon of gentling, however, these negative effects do not seem to be passed down to their children.
Female monkeys, who have been isolated in infancy, and made to have children through artificial insemination, will abandon their offspring, and even physically abuse them. It has been observed, however, that the infants of isolate mothers continue to seek maternal attention and, unless actually killed by the mother, are surprisingly successful in forming maternal attachments. Moreover, after three to four months the brutal mothers, even though they still appear to ignore the infants, may begin to behave as if they enjoy the bodily contact with the infants and their sucking for milk. Surprisingly, most of these motherless mother monkeys who subsequently have a second or third infant come to behave as normal or nearly normal mothers. Apparently, their first infants have psychiatrically rehabilitated them.
The contrast between the results of gentling versus those of isolation would appear to suggest a type of "psychobiological" filter that passes on 'positive' or evolutionary behavior traits, but limits those which are maladaptive.
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