Psychological Experiments

FACTSHEET

Animals are used not only to model physical diseases, but also to study psychological phenomena. Often, psychological experiments involve extreme suffering, and the results obtained are either species-specific or impossible to interpret, due to the highly artificial laboratory setting.

A case in point is Harry Harlow's famous maternal deprivation experiments on rhesus monkeys. In these inherently cruel experiments, young monkeys were separated from their mothers and reared in total isolation. Expectedly, the monkeys developed serious emotional disturbances – as reason itself would predict.

Apart from testing the hypothesis that maternal deprivation results in psychological and behavioral abnormalities, Harlow's experiments had another aim: to find out whether infants attach to their mothers mainly in order to obtain food (milk), or because of the pleasing touch of the mother's body. In an attempt to find out the answer to this question (which, in any case, has no clinical or applied significance), Harlow gave his maternally deprived monkeys the choice of either an artificial surrogate mother that provided a soft, comforting touch, or a surrogate mother that provided milk, but was made of uncovered wire. He also created four surrogate "monster mothers" (his own term), one of which, on schedule or demand, ejected brass spikes.

The monkeys preferred the soft-touch surrogate mother, even at the cost of remaining hungry. Harlow's conclusion was that infants attach to their mothers primarily in search of soft touch. However, his conclusions stood in contrast with clinical observations in human babies, according to which infants are attracted mainly to the milk their mothers provide, not to their body touch.

In fact, Harlow's highly artificial experiments couldn't even reveal monkeys' preferences. Giving the choice of a soothing touch or spikes plus milk hardly reflects natural phenomena. In sum, these cruel experiments – often cited as an example of the importance of psychology research on animals – are impossible to interpret. It could be that under normal conditions, monkeys and human infants alike are more attracted to the mother's milk than to her touch; it could be that rhesus monkeys and human infants differ with respect to their preferences in this respect.

The underlying problem is that in psychology research, even more than in physiology and other branches of biology, species differences render any extrapolation from animal studies to the human condition highly unreliable. Human psychology is the product of personal, social, biological, and cultural factors, which have no exact parallel in any other animal species. Furthermore, most, if not all, psychological hypotheses can be explored safely in humans, by either non-harmful experimentation on consenting volunteers, or by observational clinical research on patients.