Harlow's Experiment Regarding Maternal Contact

Harlow's questionable experiment with Rheus monkeys was a major milestone for psychology in demonstrating the relevance of maternal contact.
Harlow's Experiment Regarding Maternal Contact

Last update: 04 March, 2021

Today, for psychology and, specifically, regarding affection, the importance of maternal contact during the first months of life is evident. Among the research supporting this premise is the Harlow experiment. The results demonstrated how maternal contact influences the development of infants.

Harlow’s experiment: Touch and attachment bonding

According to developmental psychology professor Juan Delval, studies on the maternal affective systems of macaque monkeys are of great help in understanding how attachment works in people. This is because the same stages occur in apes and humans:

  • Maternal attachment and protection stage. The mother pays total attention to the offspring and watches over them continuously, satisfying all their needs.
  • Transitional or ambivalence stage. The mother continues to be attentive but begins to reprimand offspring when they manifest negative behavior.
  • Separation or rejection stage. At certain times, the mother rejects their offspring suddenly and abruptly.
    Harlow's Experiment Regarding Maternal Contact

Thus, the American psychologist Harry Harlow became interested in the importance of maternal contact. This was thanks to his colleague Van Wagenen, a doctor who showed him the intense relationships that the monkeys established with their diapers, in his studies.

As a result, Harlow studied the relationship between baby rhesus macaques and their mothers. To do so, he carried out a series of experiments that, nowadays, we would consider to be unethical.

In spite of this, the results he obtained were certainly of great importance in the world of psychology and regarding Attachment Theory. He discovered that the maternal attachment bond isn’t established through the food mothers provide, but rather through bodily contact.

“Infants possess a system of behaviors that tend toward the approximation and maintenance of contact with the adult individual who cares for them.”

 – Juan Delval –

The questionable experiment that contributed so much to psychology

In order to analyze the importance of body contact in the attachment bond, Harlow observed the behavior of baby monkeys that had been separated from their mothers. Subsequently, he locked them together with two very different wire structures, simulating supposed artificial mothers.

Harlow's Experiment Regarding Maternal Contact

Arranged side by side, one of the wire structures had a bottle attached to it, while the other was covered with foam rubber and plush only.

The results were surprising to Harlow. The baby monkeys preferred to spend more time with the soft plush structure than with the one containing the bottle that fed them, even if it meant going without food. The baby monkeys would stay with the plush surrogate mothers for up to 12 hours at a time without eating anything.

Likewise, the infant Rhesus monkey felt more secure in the presence of the plush structure, even showing exploratory tendencies. Moreover, they would come and cling to it when frightened by an unfamiliar or possibly dangerous stimulus.

Finally, despite the cruel ways in which this experiment was carried out, and the justified criticism it has received, the truth is that it turned out to be a milestone for psychology and other human behavioral sciences. Thus, it demonstrated the importance of affection and touch between a mother and her child above all else.


All cited sources were thoroughly reviewed by our team to ensure their quality, reliability, currency, and validity. The bibliography of this article was considered reliable and of academic or scientific accuracy.

  • Delval, J. (2002). El desarrollo humano. Siglo XXI. Madrid: España.

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