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The top three experiments that changed Psychology

The collective rise in our understanding of psychology has changed the way we operate as a society. From developing the code of ethics upheld in research today to building helpful frameworks for social and mental health care, it is undeniable that such research is hugely impactful to this day. Here, we discuss three of the most profound experiments that shaped our understanding of psychology, how the results were obtained, and the real-world impact of the research.

 By Elena Carruthers. Published 17 March 2021.

1. Milgram’s study of obedience

In 1961, Yale University Psychologist Stanley Milgram set out to better understand why people are more willing to obey authority figures. With the tragic events of WW2 still fresh in people’s minds, Milgram aimed to ascertain the psychology behind the atrocities that took place during the holocaust.

To achieve this, he set up an experiment using volunteers via a newspaper ad. Test subjects were given control of an electrical panel that electrocuted an individual in another room. However, they were told that the aim of the study was to test the impact of punishment on learning, ‘punishing’ people when they misremembered pairs of words. The individual in the other room was not actually being shocked, but the test subject believed they were, and this was solidified by hearing the other person’s cries of pain after each shock.

Of 40 participants, 26 willingly turned the voltage beyond 450 volts when instructed, enough to kill the other person. Milgram’s experiment made a powerful statement on people’s willingness to obey figures of authority and how people feel a diminished sense of responsibility when they are obeying orders. In addition to shedding light on the nature of obedience and the power dynamics at play during WW2, Milgram’s study also helped to open up the conversation around ethics in such studies. Now, ethical codes and practises such as informed consent are an intrinsic part of conducting psychological research.

2. Harlow’s study of attachment

Another study that made a significant impact on the field of psychology is the infamous 1958 experiment on attachment conducted by Harry Harlow. This experiment investigated the effect of a mother’s presence (or lack of) around an infant.

Harlow took a group of infant monkeys and separated them from their mothers at birth and this group was compared to those who had not been separated. The separated group were placed in cages with two surrogate mothers: a wire mother that fed the infants with an attached bottle, and one made from soft cloth that provided no food.

The findings showed that infants separated from their mothers and not given a surrogate were significantly more timid than the other group, struggled to socialise with other monkeys, and had difficulty finding mates later in life. Out of the two surrogate mothers, infants gravitated towards the cloth one and only went to the wire mother when hungry. The results emphasised the importance of tactile contact on infant’s development and broadened our understanding of attachment, allowing psychologists and social workers to better understand the effects of neglect and abandonment on young children. 

3.The Bystander Effect – Latané and Darley    

Research into ‘The Bystander Effect’ was propelled by the tragic murder of a young woman, Catherine ‘Kitty’ Genovese who was killed outside her apartment complex in Queens, New York. It was believed at the time that many witnesses saw the crime and didn’t come forward, sparking the interest of psychologists who wondered what caused this reluctance to help. Over time, the number of eyewitnesses and extent to which they dismissed the crime has been debunked. Nonetheless, Kitty’s death opened up the conversation around why people sometimes intervene to help others, and sometimes do not.

Psychologists Latané and Darley conducted a study aiming to further analyse The Bystander Effect. They recruited university students as their participants and put them in separate rooms. In these rooms, they could communicate with other people but not see them. Some only had contact with one other person, while some connected with up to five with each having two minutes to speak at a time. Little did they know, one of the voices was pre-recorded and depicted the other person having a seizure. Shockingly, only 31% of participants called for help and those in the group settings were the least likely to help, or most likely to create ‘The Bystander Effect’.

Latané and Darley (1970) proposed a five-step model explaining the conditions required for avoiding responsibility, and those required for stepping in to help:

  1. Notice (or not notice) the event.
  2. Perceive others intervening and assume it’s an emergency (or the contrary if others aren’t seen helping).
  3. Feel a sense of responsibility (or assume that bystanders will do this instead, rendering you unnecessary)
  4. Know how to assist (or feel helpless to assist)
  5. Intervene (or opt out due to fear of danger, nativity, or the assumption that others have it in hand)

This research and model helped to shape our understanding of why people seemingly lack empathy in emergency situations. Often, this is due to displaced personal responsibility. When people feel solely responsible, they are more likely to directly intervene. As recently as 2019, studies have showed that intervening is people’s intention but rather is dependent on certain conditions (such as that outlined by Latané and Darley) in order to be successful or unsuccessful.

While these studies certainly came with their ethical controversies, they established a basis from which to develop a stronger approach to ethics in research, a deeper understanding of human nature, and helped to shape the field of psychology into what it is today.


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