Instinctive Behavior And
Would a duck adopt a dog for its mother? How can a beaver build a dam identical to that of his grandfather, having never seen that type of dam? The study of animal development includes many such questions. The investigation of complex, apparently unlearned patterns of behavior in animals can also shed light upon the possible instinctive component in the development of man. Students of child development think they may have identified especially important periods in a child's life, critical periods, during which the child is particularly sensitive to certain experiences. These periods of development seem to correspond to the much better understood critical periods in animal growth. We will discuss human and infra-human critical periods in this module.
In general, the behavior of lower species, such as fish, birds, and insects, is more instinct-controlled, consistent, and predictable than man's. Lower organisms exhibit a great deal of instinctive behavior-that is, they respond to various stimuli with complicated, yet unlearned, patterns of behavior. Examples of instinctive behavior are easy to find. The spider spins a web in the same pattern used by his ancestors even if he is isolated from other spiders from birth and has no opportunity to see a web of any kind. A normal male stickleback (a small fighting fish) will attack any other male stickleback that approaches his nest, in a manner identical to the way every stickleback attacks. No reaming precedes the demonstration of the stickle back's fighting posture (Tinbergen, 1951).
Instinctive behavior involves a fixed pattern of responses that are exhibited when released by a specific stimulus. Experience has little or no effect on the pattern of instinctive behavior once it is "released" by the stimulus. The advantage to the animal is enormous; no learning is required. The disadvantages may be less apparent because most instinctive patterns have evolved into highly adaptive behavior sequences. Yet we need only to consider an experiment on the stickleback to observe obvious disadvantages.
If a male stickleback is shown a paper model of another stickleback with the red belly that signifies attack, it attacks the dummy in the usual manner. The entire attack pattern must come out in rigid sequence if it is once started. Learned response patterns, by contrast, are much more flexible and are modifiable by experience.
Some innate behavior patterns can be released by stimuli that are not as specific as the red belly of the attacking male stickleback. For example, newborn ducklings will follow a moving box or a walking human being. If they follow an object even for a short period, they will remain with it in preference to their own mother or another of their own species. This phenomenon is termed "imprinting" and includes courtship and other patterns as well as following. Imprinting is seen in insects, birds, fish, and some mammals.
Imprinting can be defined as the process by which an inborn behavioral pattern is associated with a releasing stimulus which was a result of experience. It was first named by Konrad Lorenz in 1935. Lorenz found that the following response in greylag geese is imprinted;e to a particular object only within the first few hours after birth. Each response that can be imprinted has such a critical period. The critical period is the time during which the response can be imprinted. If the critical period passes, the animal can no longer be imprinted. Hess (1959) determined the critical period for requiring the following response in chicks and ducklings using a dummy male mallard as the imprinting stimulus. He exposed each chick or duckling to the dummy for one hour and subsequently tested the strength of the imprinting response. The percentage of animals passing the test is shown in Figure 3. It is clear that the critical period for imprinting the following response occurs between 13 and 16 hours after hatching in these animals. These and other studies indicate that imprinting is a type of species-specific learning that occurs within a limited period of time (usually at a very young age) and is relatively "fixed" thereafter.
Permanent imprinting can only occur during a certain critical period in an organism's early life
Imprinting is not specific to the exact imprinting stimulus. The imprinted animal learns to follow any object or animal similar to the object on which he was imprinted. For example, a ringdove imprinted on the human hand will court any human hand, not just the hand on which it was imprinted. Wood ducks imprinted on other male wood ducks will court any male wood duck, but no female (Schultz, 1965). Finally, it is interesting to note that the imprinting experience seems to affect behavior for life. Regardless of subsequent events, the animal shows a strong preference for the kind of stimulus he was imprinted on, and never seems to "forget" or to revert to the more normal behavior for his species.
There are observations of mammalian and human behavior that suggest mechanisms similar to imprinting. In a famous study of mothering in monkeys, Harlow and Harlow (1962) raised female baby rhesus monkeys without their mothers. Each baby had a surrogate mother-a dummy made of wire mesh or terrycloth-covered wire. The babies were fed with nursing bottles attached to the dummy. Monkeys raised in this way would cling to the surrogate mother when alarmed or afraid. More interestingly, perhaps, these mother-deprived monkeys became very poor mothers when they grew up. Their social behavior with other monkeys was also disrupted.
Human infants who are deprived of the attention of a mother or mother substitute during the first year of life, and particularly in the second half of the first year, may show marked personality problems later in life (Bowlby, 1952). Normally, human infants develop attachments to the people or person caring for them during the second half of their first year of life. Prolonged institutional care can increase infant mortality and can cause harm to the social development children (Spitz and Wolf, 1965). It seems that there may be a period of time, much like the critical period, when human babies must develop a close personal attachment with one person if they are to develop normally. Erikson calls this period the time in which development of ``original trust" must take place.
The development of some human behaviors seems to depend on "critical periods."
Schaffer and Emerson (1964) measured the amount of crying or protesting made by infants when they were separated from persons with whom they were close. Their data, shown in Figure 4, indicate that non-specific attachments, formed in the early months, wane as the more specific attachments become more important. These data can be related to observations made of babies raised in institutions, where the development of specific attachments in the early months is difficult.
The critical period concept is important in some theories of child development
Clinical psychologists have long been Interested in the sensitive periods of human development. Sigmund Freud, founder of psychoanalysis, emphasized the enormous importance of early experience in the formation of personality. The Oedipal period, around the age of five, was seen by Freud as critical in sexual development. It is during this period, according to Freud, that the sexual object that will be chosen later in life Is determined. The support for Freud's theory comes from the memories of adults in analysis rather than from controlled research studies of child development. Freud and his theory will be discussed in more detail in the unit on personality. It is sufficient for our present purposes to note that theories of child development which are used by clinicians in the treatment of personality disorders take the concept of critical or sensitive periods very seriously.
PROGRESS CHECK 1
NOW DO THE EXERCISES BELOW
The behavior of humans is quite different from the behavior of lower animals. Man's ability to communicate through language both verbally and in written form enables him to be much more flexible than lower animals. The behavior of man is mainly dependent on learning, whereas behavior of lower animals is controlled more by____________________________________________________________2
Imprinting is a process in which an inborn behavior pattern becomes strongly associated with a releasing stimulus. W. M.Schein (1963) imprinted three male turkeys on people and three different male turkeys on other turkeys. Schein found that when no humans were present, all six courted other turkeys. When no other turkeys were present, they all courted humans. However,when both turkeys and humans were present the human-imprinted turkeys courted humans and the turkey-imprinted males courted turkeys. These preferences were still evident when the turkeys were five years old.
The above study illustrates that:
a. sometime during the life of these turkeys they developed preferences in courtship.
b. human-imprinted turkeys preferred following humans over other turkeys throughout their life, although in the absence of humans the turkeys would court other turkeys.
c. during the critical period, the human-imprinted turkeys reamed to follow turkeys and the turkey-imprinted turkeys learned to follow any human.
d. (none of these)_____________________________________________5
Harlow and Harlow (1962) studied the influence of an early childhood experience on monkeys' behavior as mothers. These investigators raised two groups of monkeys from birth to adulthood. The monkeys in one group, the control group, were raised by their mothers in the natural way. The experimental monkeys were deprived of their natural mothers, and mother-surrogates were presented. The investigators controlled other variables. These investigators found that monkeys raised with mother surrogates did not make good mothers. The experimental monkeys allowed their young to be removed without protest, either refused to nurse their young or would only nurse their young at a later age, and physically mistreated their young. Monkeys raised with mother-surrogates turned out to be:
PROGRESS CHECK 2
GO TO MODULE 3
March 15, 2002