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Evolution and Behaviour. Session 21. Quick Reminder!. Presentations due for Fridays session Needs to include a mind map/plan of a model exam response 5% deduction for late submissions. What is evolution?. Evolution is the changing in the inherited traits of a species over time. .
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Evolution and Behaviour Session 21
Quick Reminder! • Presentations due for Fridays session • Needs to include a mind map/plan of a model exam response • 5% deduction for late submissions
What is evolution? • Evolution is the changing in the inherited traits of a species over time.
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. • 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.
What is evolutionary psychology? • A principle of evolutionary psychology is that as genes mutate, those that are advantageous are passed down through a process of natural selection. This is derived from Charles Darwin's theory of evolution. • Evolutionary psychologists attempt to explain how certain human behaviours show how humans have developed over time. Certain behaviours can be explained by examining their evolutionary origins and their identifying their ability to enhance survival.
Activity • I am going to show you 14 images • For each picture I am going to ask you to write down the first emotion you feel when you look at the image • You may find some of these pictures unpleasant. You have the right to withdraw at any time
What emotion do you think these people are experiencing? How do you know?
Disgust: what the dictionary says... • Model Answer Intro In this essay the behaviour which will be examined in terms of an evolutionary explanation of behaviour is the study of emotions, in particular disgust. • Disgust: Noun A feeling of revulsion or profound disapproval aroused by something unpleasant or offensive.
A universal emotion? • Ekman (1972), found facial expression for disgust was identical in different cultures across the globe. • Facial expression also produced in blind individuals and is correctly interpreted by individuals born deaf. • This evidence indicates an innate biological basis for the expression and recognition of disgust. The recognition of disgust is also important among species as it has been found that when an individual sees another person looking disgusted after tasting a particular food, he or she automatically infers that the food is bad and should not be eaten. • This evidence suggests that disgust is experienced and recognized almost universally and strongly implicates its evolutionary significance.
“Yuck!” Curtis (2004) has even claimed that disgust could have been one of the first words uttered by humans. "The word 'yuck' is similar in languages all over the world. It seems to be a proto-word," says Curtis.
Fessler’s (2006) study of an evolutionary basis for disgust in pregnant women Aim: To investigate whether the ‘morning sickness’ experienced by pregnant women has an evolutionary basis. • Investigated women's experiences of nausea during pregnancy (resulting in morning sickness). • During the first trimester, hormones suppress the immune system in order to accustom the body to the foreign genetic material growing in the womb. • He hypothesised that the heightened sense of disgust experienced by women during this time was the body's way of compensating for the lacking immune system.
Fessler’s (2006) study of an evolutionary basis for disgust in pregnant women Procedure: A sample of 496 healthy pregnant women aged between 18 and 50 years old was used. The women were asked to consider 32 stomach churning scenarios such as: • Walking barefoot and stepping on an earthworm • Someone accidently sticking a fishhook through their finger • Maggots on a piece of meat in a outdoor trashcan Before asking the women to rank how disgusting they found the scenarios (using a survey), Fessler posed a series of questions, designed to determine whether they were experiencing morning sickness.
Fessler’s (2006) study of an evolutionary basis for disgust in pregnant women Findings & Conclusions: Women in the first trimester of their pregnancy scored much higher on scores across the board on disgust sensitivity than their counterparts in the second and third trimester. They found the scenarios involving food most disgusting. As many of the most harmful diseases are food-borne, Fessler concluded that a heightened sense of disgust was advantageous to our ancestors and allowed them to survive long enough to produce offspring, who passed on the same sensitivities. It would have helped compensate for the increase susceptibility to disease during early pregnancy, which is a risky period due to the suppressed immune system, by increasing the urge to be picky abut food.
Fessler’s (2006) study of an evolutionary basis for disgust in pregnant women Evaluation This study supports the role of disgust in aiding reproduction, and thus, as an evolutionary behaviour. 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 when using statistical significance).
Links back to the question • Fessler’s study supports that disgust may be an evolutionary behaviour as it may assist reproduction of offspring and protection against disease, thus having a greater chance of surviving or living a longer life, having children passing on genes to their offspring.
Curtis et al. (2004) Internet survey on disgust responses Aim: Aim To carry out research on the Internet to test whether there were patterns in people’s disgust responses.
Curtis et al. (2004) Internet survey on disgust responses Aim: Procedure: Used an online survey in which participants were shown 20 images. Participants were asked to rank their level of disgust. Among the 20 images were seven pairs in which one was infectious or potentially harmful to the immune system, and the other was visually similar but non-infectious—for example, one pair was a plate of bodily fluids and a plate of blue viscous liquid. There were 77 000 participants from 165 countries.
Curtis et al. (2004) Internet survey on disgust responses Disgust reaction was most strongly elicited for those images which threaten one’s immune system. • Natural selection may have helped human ancestors to be more disgusted at things which threatened the immune system to avoid things that could potentially lead to diseases. Women had higher disgust reactions than men. • As women are carriers for offspring, they have a stronger disgust reaction so as not to threaten the lives of unborn offspring. The disgust reaction also decreased with age. The decrease of disgust with age may be explained by the fact that the older a member of a species, the less likely they are to reproduce.
Curtis et al. (2004) Internet survey on disgust responses Evaluation • Curtis used 77 000 participants from 165 countries. Large sample size and cross cultural = generalisable • Provides support for Fessler et al (2005) and vice versa • Self report measures of disgust = subjective
Links back to question • Curtis (2004) study supports the role of disgust in aiding reproduction, and thus, as an evolutionary behaviour.
But do we find everything disgusting? • But we can override the disgust response. • People find family less disgusting than strangers. • And when it comes to sex, we compromise between our instinctive avoidance of disease and our urge to reproduce.
Other factors influencing disgust • Recent research has also suggested that sensitivity to disgust is related to ethnocentrism (Navarrete & Fessler, 2006) as well as various politically conservative issues including abortion, immigration, homosexual marriage and stem-cell research, as well as prejudice toward homosexuals. • Disgust sensitivity has also been found to be correlated with other variables such as right-wing authoritarianism, religious fundamentalism (Terrizzi & Ventis, 2006) and religious obsessions (Olatunji, Tolin, Huppert & Lohr, 2005). *Ethnocentrism is judging another culture solely by the values and standards of one's own culture.
Evaluative points for evolutionary theory In spite of such evidence, there are some things to consider when examining an evolutionary argument. • The theories are speculative – its difficult to carry out experiments to clearly prove the theories • Since it may be difficult to test empirically some evolution-based theories, researchers may be susceptible to confirmation bias— that is, they see what they expect to see. The researcher Hayes (2005)states that there is a tendency to ignore findings that don’t fit in with the theory confirmation bias • Little is known about the behaviour of early Homo sapiens, sostatements about how humans used to be are hypothetical. • Evolutionary arguments often underestimate the role of culture/nurture/the present environmental influences in shaping behavior.
Conclusions? • There is some evidence to support evolutionary explanation of disgust • Fessler (2006) showed that disgust may be an evolutionary behaviour as it may assist reproduction of offspring by compensating for a suppressed immune system. • Curtis et al. (2004) found that the disgust reaction may help to prevent sicknesses. • Research suggests that disgust aids the survival of the human species and is therefore an evolutionary behaviour. • Also need to consider other factors such as the environment
Disgust Scale Want to take part in some online disgust research? http://www.yourmorals.org/explore.php
