Explain how the perspectives of behaviourism can account for the learning and behavioural
differences seen between the twins in the following case study:
Dizygotic twins Sarah and Sandra
Sarah was born slightly heavier than Sandra and her weight advantage gradually increased during
their development. By preadolescence, her weight was recognised as a problem by the family and
she generally felt fat and ugly, constantly regarded as the “fat twin.” Sarah was notoriously
compulsive; she ate lunch every day at precisely 1pm, went to bed at exactly the same time every
night and wore the same style of clothes daily. She was often criticised by her family for her
routine lifestyle. Sarah was extremely independent throughout her development. As a child and
into adolescence, she preferred her own company, and her parents generally left her to her own
devices, which consisted mainly of reading as she was an avid reader. She later became an author.
Sarah was self-contained and given to outbursts particularly towards her younger sister and this
was met with strong rebuke from her mother. This made her very resentful towards her parents.
Sarah was always more sensitive to stressful situations, for example, her family had to move to a
new town and Sarah struggled to adapt to the new environment and often cried herself to sleep
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and acted out in school. In an attempt to make her feel better, her parents would buy her gifts.
Subsequently, during her teenage years, Sarah’s behaviour became highly problematic; she
changed from the “model daughter” to a stubborn, irritable and disobedient individual.
Sandra on the other hand, was extremely physical from a young age, she was an extremely gifted
dancer and acrobat, skills she honed throughout her development and eventually became a dance
instructor. Sandra was more impulsive than her sister and was affectionately considered a
prankster by her family. As an infant she was cuddly, happy and even-tempered and she
continued to be warm and sociable throughout her development and her parents constantly
played board games with her and interacted with her. Her father even taught her how to fish
when she was 10 years old.
Sandra was more openly affectionate than Sarah, a trait that she shared with her mother.
Sandra’s adolescence was smooth as she coped well with the family’s move to a new town. She
quickly made new friends, joined the dance team and was liked by most of her teachers. Although
both girls were of similar intelligence, Sandra received slightly higher grades and was constantly
awarded trophies and prizes at school for her work and was praised by her family for her
achievements.
The above case study was adapted from Frank, R. A., & Cohen, D. J. (1980). Preadolescent
development: case studies in twins. The Yale Journal of Biology and Medicine, 53(6), 471-483.
Starting references:
For this assignment, you are required to utilise the reading provided in addition to providing at least
four more peer-reviewed articles.
Frank, R. A. and Cohen, D. J. (1980). Preadolescent development: case studies in twins. The Yale
Journal of Biology and Medicine, 53(6), 471-483
