Animal studies

Animal studies

1. Lorenz (1935)- Imprinting

   • Lorenz divided a clutch of eggs in two halves: one half was left to hatch with the mother (the control group). The other half were hatched in an incubator, the first moving thing they saw was Lorenz.
   • Results: The control group followed their mother goose everywhere whereas the second group followed Lorenz. Lorenz' goslings showed no recognition of their real mother.
   • Lorenz, in some of his experiments, got young ducks and goslings to imprint on inanimate objects such as wellington boots.
   • Stephen Lea (1984) proposed that instinct gives the chicks the concept or template of the mother but the environment has to supply the details
   • Lorenz also observed that birds that imprinted on humans then displayed courtship behaviour towards humans when adults (Sexual imprinting). However Guiton (1966) found that though this was the case with chickens imprinted on washing up gloves they eventually learnt to mate with their own species.

2. Harlow (1958) – Effects of privation

   • 16 monkeys were separated from their mothers immediately after birth and placed in cages with access to two surrogate mothers, one made of wire and one covered in soft terry towelling cloth. Eight of the monkeys could get milk from the wire mother and eight monkeys could get milk from the cloth mother.
   • Both groups of monkeys spent more time with the cloth mother (even if she had no milk). The infants of the second group would only go to the wire mother when hungry. Once fed they would return to the cloth mother for most of the day. If a frightening object was placed in the cage the infant took refuge with the cloth mother. The infant would explore more when the cloth mother was present.
   • Then Harlow observed the difference in behaviour differences between the monkeys who had grown up with surrogate mothers and those with normal mothers
     • They found that: They were much more timid, they didn’t know how to behave with other monkeys and could be aggressive, they had difficulty with mating and the females were “inadequate” mothers some even killing their offspring.
     • These behaviours were observed only in the monkeys who were left with the surrogate mothers for more than 90 days. For those left less than 90 days the effects could be reversed if placed in a normal environment where they could form attachments.
   • Harlow concluded that “contact comfort” (provided by the cloth mother) was more important than food in the formation of attachment. This also shows that contact comfort is preferable to food but not sufficient for healthy development. He also concluded that early maternal deprivation leads to emotional damage but that its impact could be reversed in monkeys if an attachment was made before the end of the critical period. However if maternal deprivation lasted after the end of the critical period then no amount of exposure to mothers or peers could alter the emotional damage that had already occurred.