Evolutionary Psychology
Examine one evolutionary
explanation of behavior.
Darwin’s Theory of Evolution
• Based on the
assumption that living
organisms face
environmental
challenges.
• Organisms that adapt
the best have a greater
chance of passing there
genes to the next
generations.
Darwin’s Theory of Evolution
• Organisms with specific
genetic traits that
enhance survival are said
to be naturally selected.
• They are more likely to
survive and pass those
traits on.
• Many of the traits that
you have been passed
down to you to help you
survive.
Disgust in Pregnant Women
• Nausea and loss of
appetite may have been
evolved as a way to
protect the mother and
the fetus against diseases
which could threaten the
fetus.
• Disgust has evolved as
food rejection response
to prevent contamination
and the spread of illness.
Fessler et al (2005)
Elevated disgust sensitivity in the first trimester or pregnancy
Aim:
• To investigate if disgust
sensitivity in the first
trimester of pregnancy
was elevated as
predicted.
Fessler et al (2005)
Elevated disgust sensitivity in the first trimester or pregnancy
Procedure:
• A web based survey was
completed by 691
women recruited
through pregnancy
related web sites.
• No compensation was
offered.
• The women’s mean age
was 28.1 years.
Fessler et al (2005)
Elevated disgust sensitivity in the first trimester or pregnancy
Procedure:
• On the questionnaire
the participants:
– Indicated current level of
nausea on a 16 point
scale
– Answered questions to
discuss their disgust
sensitivity in 8 areas
(food, contact with
animals, dead animals,
hygiene, toilets etc..)
Fessler et al (2005)
Elevated disgust sensitivity in the first trimester or pregnancy
Results
• Overall, sensitivity for
food and body products
was higher in 1st
trimester compared to
2nd and 3rd.
• Disgust was highest
with food (as was
predicted).
Fessler et al (2005)
Elevated disgust sensitivity in the first trimester or pregnancy
Results:
• Food-borne diseases are
particularly dangerous for
women in the 1st trimester,
so it was predicted that the
sensitively would be high
(they were right).
• The results may indicate
that nausea and vomiting
are evolved behaviors
because they limit the
likelihood of a pregnant
woman eat dangerous food.
Fessler et al (2005)
Elevated disgust sensitivity in the first trimester or pregnancy
Evaluation:
• The data was collected
through questionnaires. Self
reports may not be a great
way of measuring disgust.
• It would have been better to
confront them with real
disgust-eliciting objects.
• The effect was big (but not
hugely significant).
• Curtiss et al (2004) showed
that images that threaten the
immune system are judged as
more disgusting.