DeBellis 2001- Sex Differences

Aims, Procedure, Findings, Conclusion, Evaluation

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Sex Differences in Brain Maturation during Childhood and Adulthood
DeBellis et al ­ 2001
To investigate sex differences in brain development, looking at grey matter (which is cell
bodies and synapses), white matter (axons) and an area called the corpus callosum (which
is the part of the brain that links the left and the right sides of the brain).
Sample: 61 males 57 female (children ages 6-17) obtained using volunteer sample
(advertised in the local community Pittsburgh, USA).
Children assessed for: cognitive abilities, handedness, intelligence (via IQ), socioeconomic
status and ethnicity. There were no differences between males and females in terms of IQ,
age, handedness, socioeconomic status, and ethnicity. The boys were taller than the girls in
general. Most participants had a higher IQ than average.
A full written description of the study was given to parents, and participants, and full written
consent was given.
Brain Volumes were measured using an MRI scanner. The participants went through a
simulator first, so they were used to the sight and sounds. They were allowed to watch their
favourite film when in the scanner, and also were given a bribe that they could see a picture
of their brain, if they promised to stay still.
The volumes were assessed by raters who were in a blind condition (unaware of the sex of
participants). There was high inter rather reliability between raters of 0.98 and 0.99, in each
The volume of grey matter significantly fell with age, more so in males than in females.
The volumes of white matter and the corpus callosum increased with ages, more so in
The differences were significant in white matter and corpus callosum.
There wasn't a significant change on cerebral volume between ages; there was a significant
difference between males and females. This was taken into account.
As boys show faster changes (loss of grey matter, increase of white matter and corpus
callosum volume) this shows boys brain mature faster than female brains.
One of these reasons could be linked to hormones. Oestrogen delays pruning, but
testosterone promotes myelination.
These differences can help to explain gender difference in cognitive abilities. Also, helps to
see the patterns of development as males and females mature.
It can also help to explain gender related differences in early development disorders like
autism and ADHD.
Strengths Weaknesses
Uses of MRI scans are very accurate, objective and It was a cross sectional study, but a longitudinal study
reliable. may have been more appropriate.
Consent was given from the parents and the Lab experiment so low in ecological validity.
participants themselves. Environmental Factors and Learning factors weren't
Large Sample. taken into account; these could have caused the brain
Results are reliable as they could be replicated differences.
because of the tight controls over the variables. Volunteer sample isn't representative.

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