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.