BLA Study - Tetsuro Matsuzawa (2007)

Evolutionary Psychology: Animal Researches

Tetsuro Matsuzawa (2007) Primate Studies on Spatial Memory Skills

Darwin suggested the theory of natural selection, which infers that any change in a trait, if useful, will be kept. The change in a trait is a result of a need to adapt to ever-changing environments, and in order to make the most out of the limited environments. Along with this theory, Darwin also believed that humans were very similar to primates, and had similar behaviors. These behaviors included: mate selection, maternal love and self-preservation. He also said that primates and humans shared similar emotions and facial expressions. These assertions suggest that studying animal behavior will give us insight to human behavior. 

An example of this claim is a study by Tetsuro Matsuzawa of Kyoto University (2007). Tetsuro Matsuzawa studied the spatial memory skills of chimps and humans. He had trained three pairs of chimpanzees to recognize the numbers 1-9 on a computer monitor. He then took the chimp subjects and the human subjects and directed them to sit at computer terminals. The computer monitors would briefly flash the numbers 1-9 on the screen, and then the numbers would be hidden by blank white squares. The subjects were instructed to select the blank white squares in the order of 1-9. With each trial, the period of time where the numbers were actually visible was shortened. As a result, humans made more and more errors as the intervals between numbers and white squares were shortened. However, the chimps showed remarkable spatial memory skills, and were able to accurately select the squares in the correct order even when the intervals were shortened. 

Tetsuro Matsuzawa concluded that this was a representation of adaptation to each of the subjects' species's respective environments. Chimps needed remarkable spatial memory skills to survive in the jungle: they needed to remember where food resources, and danger, was located in the rain forest. As agriculture developed, humans' needs for spatial memory skills lessened, and were replaced by language memory skills. Humans need the capacity to remember language much more than spatial memory skills. These reasons explain why and how adaptation takes place, and how animal researches can help us understand human behavior.

BLA - Mock Exam

Examine how the theory of evolution has made an impact on the biological level of analysis. Consider either cultural or historical conditions.

Evolution is a theory first suggested by Charles Darwin. Charles Darwin believed that the environment presented challenges to the individual, needed to adapt in order to survive. He stated that the traits and characteristics that allowed an individual survive in his ever-changing environment were the ones that were passed on to offspring over generations. Charles Darwin called this state the "theory of natural selection", and the act of a species changing in concordance to its environment "adaptation".

Charles Darwin first thought of these theories when he was visited the Galapagos Islands. He noticed that the finches on each island had slightly different beak shapes from finches on other islands. Darwin concluded that this was an adaptation on behalf of the finches, where they had the most advantageous beaks that helped them acquire food in their respective environments. However, Charles Darwin was unaware of how exactly the genes and traits of the finches were passed on to their offspring.

Charles Darwin heavily influenced the biological perspective in psychology with his theories of evolution, natural selection and adaptation. A branch of psychology, known as 'evolutionary psychology' was directly influenced by Darwin's suggested theories of evolution.

Evolutionary psychology is a branch of psychology believes that particular advantageous traits that allow organisms to survive in their ever-changing environments are passed on to offspring, and eventually are passed down on to us. (The theory of natural selection is widely accepted as a basis in evolutionary psychology) Therefore, evolutionary psychology views that there are mechanisms and factors that affect our behavior - and these mechanisms are those that we acquired from our ancestors over a course of hundreds of years. 

Evolutionary psychology often focuses on the biological factors and mechanisms of behavior, which is something Darwin was not able to do. Fessler et al (2006) studied the evolutionary level of behavior. Fessler predicted that women in first trimester pregnancy would have higher disgust sensitivity levels than women in other periods of pregnancy. Fessler believed that women in early pregnancy experienced nausea and vomiting as a defense mechanism - in order to protect themselves from eating dangerous foods, which are the roots of food-borne diseases. He predicted that this food-rejection was a result of adaptation - our ancestors needed to avoid food-borne diseases to live long enough to create offspring and passed their traits down to their offspring. The trait of food-rejection in order to prevent food-borne diseases was one characteristic that was passed down onto humans today.

Fessler created an online-based survey with the purpose of studying the levels of disgust sensitivity in pregnant women. 691 women were recruited off pregnancy-related websites, and 496 of these women's survey answers were used. The first part of the survey had the women rate their nausea levels on a scale of 1 - 16. The second part was a questionnaire-survey that studied the women's disgust sensitivity on 8 different levels. (8 levels: involved photos of food, hygiene, animals, etc.)

As a result, Fessler found that women in the first trimester of their pregnancy had overall higher disgust sensitivity levels compared to other pregnant women. Particularly, these first trimester pregnant women had high disgust responses with photos of food. Fessler concluded that this was a result of an adapted behavior in order to protect the mother from dangerous foods that could be causes of food-borne diseases. He suggested that the trait was first developed by our ancestors in order to protect themselves and their offspring, and that it was passed on to us. This study is a remarkable representation of evolutionary psychology and adaptive tendencies. Like this, evolution as a concept helped psychologists understand the mechanisms and origins of some behaviors such as disgust. Psychologists, who are inclined in nature to focus on environmental and cultural conditions to analyze behavior had their eyes opened by the theories of evolutionary psychology. Behaviors not only had biological origins, but are also results of natural selection.

Evolutionary psychology has contributed to the biological level of analysis because it allows researchers test whether there are biological origins to behavior, and how animals could have similar behavioral tendencies as humans. These are the two major principles in the biological level of analysis: 1) There are biological correlates to behavior, 2) Animal researches can help us understand human behavior. One negative aspect of evolutionary psychology is the fact that it tends to underestimate cultural conditions in the analysis of behavior. However, it helps us understand the roots of some mechanisms of behavior and gain insight to human behavior. 

BLA - Evolution

2.2 The Biological Level of Analysis: Genetics and Behavior

Adaptation
The environment presents challenges to the individual. In order to survive, these individuals needed to adapt best to the environment.
By adapting, individuals would have greater chances of:

• Surviving
• Reproducing
• Passing genes on to offspring

Charles Darwin's theory of evolution and natural selection explains how species acquire adaptive characteristics to survive in ever-changing environments. According to Darwin's theory of natural selection, members of a species that are able to adapt to the environment are more likely to breed and pass on their genes to offspring.

During his travel to the Galapagos Islands, Charles Darwin noticed that the finches on different islands had slightly different beak shapes. He found out that each type of finch had the beak-type that was most advantageous to its own environment - better suited to eat the food that was available on its island.

Therefore, Darwin concluded that adaptation was a process that helps species develop characteristics that make it more competitive in that environment. However, when Darwin presented this theory in his journal, On the Origin of Species, he was not aware of the biological factors through which traits and characteristics can be inherited.

^Principle: "there are biological correlates to behavior"

Animal Researches and Evolution

Charles Darwin also laid the foundation for psychologists and biologists that animal research and studies can help gain insight to human behavior. Humans have a number of traits and principles that are similar to animals, especially apes and monkeys. The similarities include:

• Mate selection
• Maternal love
• Self-preservation

Darwin also noted that there are facial expressions and emotions that humans have that are in concordance to apes.

Study: Tetsuro Matsuzawa (Kyoto University) 2007

Brief: A study on spatial memory on chimps

Three pairs of chimps were selected and taught to memorize the numbers 1-9 on a monitor. Humans and chimps were placed to sit in front of a computer monitor, where the numbers 1-9 would appear (in a random order) for a brief period, and disappear, only to be replaced by blank slates. Subjects were directed to select the slates in the order which the numbers appears at their respective locations. They had to touch the slates in the appropriate sequence.

Result: As the time that the numbers on the screen appeared shortened, humans were unsuccessful in remembering the sequential order and selecting the correct slates in order. They made many errors. The chimps showed a remarkable spatial memory ability - selecting the correct slates even when the time that the numbers were shown was shortened.

Interpretation: Chimps had strong spatial memory abilities because they need the skill to survive in the jungle. They need to remember where food resources and dangers are in the rain-forest. Humans, on the other hand, do not need as much of this skill because of their urban environment. As agriculture developed, the skill of spatial memory was no longer an essential skill for human survival. However, to compensate, humans have a remarkable language ability that chimps do not. It appears that the memory skills of each organism were used in different ways - humans with language, chimps with spatial recognition. The organisms adapted to become more suitable to their respective environments.

^Principle: "animal researches can help us understand human behavior"

Evolutionary Psychology

Evolutionary psychology is based on the belief that as genes mutate, those that are advantageous are passed down to new generations. This is based on the belief of natural selection.
Evolutionary psychologists attempt to find human behaviors that can be used as proof of how our species has developed over time. Natural selection can select for mechanisms and functions that are correlated to behavior.

Study: Fessler et. al (UCLA) 2006.

Brief: A study on the sensation of disgust in first trimester pregnancy. "The sensation of disgust helped our ancestors avoid illnesses that are food-borne and survive long enough to produce offspring. These ancestors then passed on these genes to us." (Fessler, 2006)

Aim: To investigate if the sensation of disgust in the first trimester of pregnancy was elevated. (= Hypothesis)

Procedure: Web-based survey that was completed by 691 women who are pregnant. These women were recruited via pregnancy-related sites on the internet. No compensation was provided in this experiment. The subjects were (on average) 28.1 years old.

496 subjects' answers on the survey were used. (They had to be healthy with no chronic illness, above 18 and below 50 years of age, and answer all questions on the survey.) The subjects stated their level of nausea on a 16 point scale. Then, they answered a questionnaire to test their disgust sensitivity in 8 areas.

Result: Women in their first trimester of pregnancy had elevated levels of disgust, generally in all areas. However, the level of disgust was highest in the area that involved food. Food-borne diseases are especially harmful to women in first trimester pregnancy. Consumption of spoiled foods (etc.) could result in illness, or death, to both the mother and child. Nausea and vomiting when in contact with food is an adaptive behavior that was acquired from evolution in order to prevent mothers from eating dangerous foods.

Evaluation: Subjects were liable to lie due to the method of the study. Many samples were acquired, presumably accurate data processing.

Things to Consider / Studies of Evolutionary Psychology:

• Difficult to test theories because we do not know about the lives of early humans
• Researchers interpret the data in a way they expect: confirmation bias
• Evolutionary psychology underestimates cultural influences of behavior

Resources used: 

Psychology Course Companion (Crane)

Psychology for the IB Diploma (Pearson Education)

Course Companion Outcomes Glossary