Principles of the Biological Level of Analysis

Bennett

IB Psychology

Biological Level of Analysis
Review

Principles of the biological level of analysis

1. Behavior can be innate because it is genetically based. If this principle is accepted it is logical to believe that evolution may play a key role in behavior.
2. Animal research can provide insight into human behavior; as a result, a significant amount of research is undertaken using animals.
3. There are biological correlates of behavior. The implication of this is that it should be possible to fins a link between a specific biological factor (e.g. a hormone) and a specific behavior, and this is the aim of researchers working at the biological level of analysis.

Researchers look at how cognition and the environment interact with biological systems and affect physiology. This relationship is bidirectional (i.e. biology can affect cognition and cognition can affect biology.

Nature versus Nurture Debate – researchers debate whether human behavior is the result of biological or environmental factors.

The interactionist approach used by modern psychologists does not solely rely on either nature (biological) or nurture (environment), but adopts a more holistic picture of human behavior. This is the goal of IB psychology.

Physiology and Behavior

Mechanisms of neurotransmission and their effects on human behavior

Neuron- a nerve cell; the basic building block of the nervous system.

Neurotransmission – the method by which neuron send electrochemical messages to the brain to that people respond to stimuli – wither from the environment or from internal changes in the body.

Dendrite - the bushy, branching extensions of a neuron that receive messages and conduct impulses toward the cell body.

Axon - the extension of a neuron, ending in branching terminal fibers, through which messages are sent to other neurons or to muscles or glands.

Myelin [MY-uh-lin] Sheath - a layer of fatty cells segmentally encasing the fibers of many neurons; enables vastly greater transmission speed of neutral impulses.

Synapse [SIN-aps] - junction between the axon tip of the sending neuron and the dendrite or cell body of the receiving neuron; tiny gap at this junction is called the synaptic gap or cleft.

Neurotransmitters- chemical messengers, when released by the sending neuron, neurotransmitters travel across the synapse and bind to receptor sites on the receiving neuron, thereby influencing whether it will generate a neural impulse.

How neurotransmitters can affect behavior

Kasamatsu and Hirai (1999) – aim of study was to see how sensorydeprivation affects the brain. Buddhist monks who went on a 72-hour pilgrimage to a holy mountain in Japan were studied. During their stay on the mountain, the monks did not consume food or water, they did not speak, and they were exposed to the cold. After about 48 hours, they began to have hallucinations (often seeing ancient ancestors or feeling a presence at their side.) Researchers took blood samples before the monks ascended the mountain and again immediately after the monks reported hallucinations. They found that serotonin levels had increased in the monks’ brains. These higher levels of serotonin activated the hypothalamus and frontal cortex of the brain resulting in hallucinations.

The brain and behavior

Prior to the development of modern scanning technology, one of the most common ways to study the brain was the use of case studies of brain damage. Case studies of brain damaged patients are often carried out longitudinally- that is over a long period of time in order to observe the shorttermand long term effects of damage.

Case Study: Phineas P. Gage (1823 – 1860) was an American railroad construction foreman now remembered for his incredible survival of an accident in which a large iron rod was driven completely through his head, destroying much of his brain's left frontal lobe, and for that injury's reported effects on his personality and behavior—effects so profound that friends saw him as "no longer Gage."

Localization of brain function

Paul Broca (1861) found that people suffering from brain damage in the left frontal lobe of the brain were unable to understand and make grammatical complex sentences. This area is called Broca’s Area.

Broca’s aphasia – condition where the people had problem’s producing speech, but were able to understand it. Broca’s most famous patient was Tan. He used Tan’s case study to support his claims. This name was Tan because that was the only word he could say. After death, an autopsy revealed the source of his rain damage that the disability was the result of a specific brain trauma.

Carl Wernicke’s(1847) first described the area that appears to be crucial for language comprehension – the left posterior superior gyrus (this is called Wernicke’s area.) Wernicke’s patients could produce speech, nut could not understand it. This condition is known as Wernicke’s aphasia.

By carrying out post-mortem studies of people who had suffered from strokes, Broca and Wernicke came to the conclusion that language processing is localized. When a behavior is localized in the brain, it is possible to trace the origin of the behavior to a specific part of the brain. Studies of localization function led to the desire to map out the brain’s functions. Though localization does not explain all human behavior.

Below: Brain activity when hearing, seeing, and speaking words

Localization of brain function and ethics in research

In the 1950s, Robert Heath performed many controversial experiments involving electrical stimulation of the brain (SB). He found that by electrically stimulating specific parts of the brain of depressed patients, they would experience pleasure. He let the participants press the button themselves to experience pleasure. During a three-hour session, the subject, code-named B-19, electrically self-stimulated his reward circuitry some 1,500 times. “During these sessions, B-19 stimulated himself to a point that he was experiencing an almost overwhelming euphoria and elation, and had to be disconnected, despite his vigorous protests."

At the same time, JamesOlds carried out research on rats to see what could happen if their pleasure centers were stimulated. He devised an experiment in which the rat would receive electrical stimulation of the nucleus accumbens by pressing a lever. It was found that the rats were willing to walk across electrified grids in order to get to the “pleasure lever.” In fact, they even preferred the stimulation to eating and drinking.

The use of technology in brain research

Modern technology is used extensively in neuropsychology because it provides an opportunity to study the active brain. However, experiments with animals are still extensively used in brain research because they allow psychologists to study specific biological correlates of behavior using invasive techniques. Early experiments on the brain involved invasive techniques – for example removing (abalation) or scarring (lesioning) brain tissue in order to study behavioral changes, behavior before and after lesioning was compared.

Hetherington and Ranson(1942) conducted one of the first experiments studying regulation of feeding behavior. They lesioned a part of a rat’s brains. They found that lesions in the lateral hypothalamus caused the rats to stop eating, while lesions in the ventromedial hypothalamus caused the animals to overeat, leading to obesity.

Electroencephalogram (EEG) an amplified recording of the waves of electrical activity that sweep across the brain’s surface; these waves are measured by electrodes placed on the scalp.

CT (computed tomography) Scan a series of x-ray photographs taken from different angles and combined by computer into a composite representation of a slice through the body; also called CAT scan.

PET (positron emission tomography) Scan a visual display of brain activity that detects where a radioactive form of glucose goes while the brain performs a given task.

MRI (magnetic resonance imaging) a technique that uses magnetic fields and radio waves to produce computer-generated images that distinguish among different types of soft tissue; allows us to see structures within the brain.

How the environment affects the brain

Brain plasticity - the brain’s capacity for modification, as evident in brain reorganization following damage (especially in children) and in experiments on the effects of experience on brain development.

Every time we learn something new, the neurons connect to create a new trace in the brain. This is called dendrite branching because the dendrites of the neurons grow in numbers and connect with the other neurons.

One of the most well known claims of brain plasticity is the Mozart Effect. Rauscher et. al (1993) investigated the effect of listening to music by Mozart on spatial reasoning. They gave research participants one of three standard tests of abstract spatial reasoning after they had experienced each of three listening conditions: a sonata by Mozart, repetitive relaxation music, and silence. They found a temporary enhancement of spatial-temporal reasoning, as measured by the Stanford-Binet IQ test. By simply listening to the music, the brain will develop a more sophisticated ability to solve spatial problems.

A mirror neuron is a neuron that fires both when an animal or human acts and when the animal or human observes the same action performed by another. Thus, the neuron "mirrors" the behavior of the other, as though the observer were itself acting. Such neurons have been directly observed in animals and humans. Mirror neurons may play a vital role in the ability to learn from – as well as empathize with another person.

Functions of hormones in human behavior

Hormonesarechemical messengers, mostly those manufactured by the endocrine glands that are produced in one tissue and affect another.

The Endocrine System

Some hormones and their functions

Hormone / Glands / Function
Adrenaline / Adrenals / Flight or flight response, arousal
Cortisol / Adrenals / Arousal, stress hormone, memory
Melatonin / Pineal / Regulation of sleep
Oxytocin / Pituitary and hypothalamus / Mother-child attachment
Testosterone and estrogen / Gonads / Development, emotion

Rosenthal (1987) found that higher levels of melatonin contribute to seasonal affective disorder (SAD) – a subcategory of depression that is characterized by sleepiness and lethargy – as well as craving for carbohydrates. Reduced levels of sunlight in fall and winter are believed to disrupt circadian rhythms in certain people leading to this form of depression.

Genetics and Behavior

Behavioral genetics

Behavioral Genetics–deals with understanding how both genetics and the environment contribute to individual variations in human behavior.

Psychologists argue that an individual may have a predisposition to a certain behavior; however without the appropriate environmental stimuli, this behavior will not be manifested.

Genetic arguments of behavior are based on the principle of inheritance. Genes and their DNA are passed down from parents to their offspring.

Chromosomes- threadlike structures made of DNA that contains the genes.

DNA (deoxyribonucleic acid)- complex molecule containing the genetic information that makes up the chromosomes; has two strands-forming a “double helix”--held together by bonds between pairs of nucleotides

Genes- biochemical units of heredity that make up the chromosomes; a segment of DNA capable of synthesizing a protein

Genetic Research

Genetic research in humans is to a large extent based on correlational studies. Researchers look at how different variables may co-vary. This means that a correlational study establishes that there is a relationship between variables, but the researcher does not manipulate the independent variable as in an experiment. Therefore no cause and effect can be determined.

Twin studies, family studies and adoption studies

Monozygotic (Identical Twins) MZ- develop from a single fertilized egg that splits in two, creating two genetically identical organisms.

Dizygotic (Fraternal Twins) DZ-develop from separate eggs; genetically no closer than brothers and sisters, but they share the fetal environment.

Twin Studies

Identical twins: Identical genes

• Prenatal environment: nearly same
• Environmental

•A: Raise in birth family: similar environment

•B: Separated at birth and adopted: different environments

• Variability between identical twins in adopted families is measure of environmental + genetic influence
• Variability between identical twins raised together is measure of genetic influence (mostly).
• Epigenetic (study of inherited changes in appearance) changes contribute to differences between identical twins:

•infant twins show few differences in number of genes that have been turned on or shut down

•elderly twins show a large number of differences

The Minnesota Study of Twins Reared Apart

In 1979, Thomas Bouchard began to study twins who were separated at birth and raised in different families. Bouchard found that an identical twin reared away from his or her co-twin seems to have about an equal chance of being similar to the co-twin in terms of personality, interests, and attitudes as one who has been reared with his or her co-twin. This leads to the conclusion that the similarities between twins are due to genes, not environment, since the differences between twins reared apart must be due totally to the environment.

MZ Twins raised apart are about as similar as twins raised together in personality and temperament, activity levels, interests, intelligence and attitudes, even some EEG patterns and psychological disorders.

DZ twins vary a lot more, together or apart. Home environment has little impact on these variables; they appear to be determined by genetics to a great degree.

Criticisms of twin studies:

• Identical twins have same or highly similar prenatal environments
• Adoptive parents are often selected to be similar in background, social status and intelligence to biological parents: variation in environments between separated, adopted twins is often small
• Identical twins, because they look and initially behave alike, may evoke similar responses from people in their environment.
• Researchers of twins may be biased more towards seeing traits in common vs. traits that differ

Family studiesare another way that behavioral genetics are studied. It is a more general representative sample of the general population. Children have 50/50 of mother and father’s genetics.

Adoption studies allow for the most direct comparison of genetic behaviors and environmental influences. Adopted children generally share none of their genes with adoptive parents, focuses on effect of environment. Adoption agencies use selective placement with adoptions and try to place the child in with families that are similar to biological parents.

Evolution

Darwin’s theory of natural selection explains how species acquire adaptive characteristics to survive in an ever-changing environment. According to natural selection those members of a species who have characteristics which are better suited to the environment will be more likely to breed.

Adaptation – over several generations the results of natural selection is that species develops characteristics that make it a more competitive environment.

Evolutionary Psychology

The goal of research in evolutionary psychology is to discover and understand the design of the human mind. Evolutionary psychology is an approach to psychology, in which knowledge and principles from evolutionary biology are put to use in research on the structure of the human mind. In this view, the mind is a set of information-processing machines that were designed by natural selection to solve adaptive problems faced by our hunter-gatherer ancestors. According to evolutionary psychologists, all organisms, including humans, are “gene-producing machines” with the basic motivation of perpetuating their own genetic pool. Our genes predispose us to act in ways that enhance their chances of surviving and spreading. This motive underlines all our behavior.

Criticisms of evolutionary psychology:

• 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.
• Little is known about the behavior of early homo sapiens, so statements about how humans “used to be” are hypothetical.
• Evolutionary arguments often underestimate the role of cultural influences in shaping behavior.

An integrative look at criminal behavior

Modern researchers argue that no one is born to be a criminal, but that various biological factors can contribute to criminality. There are several theories regarding the biological nature of criminality: genetics, brain abnormalities, and neurochemical imbalances.

Genetics

Genetic influences also have been implicated in non-violent forms of antisocial and criminal behavior. Twin studies (Rowe, 1983) and adoption/cross-fostering studies (Hutchings & Mednick, 1975) have shown that antisocial and criminal behavior is in part genetically determined. In their adoptee study, Mednick, Gabrielli, and Hutchings (1984) assessed court convictions of 14,427 adoptees and whether their biological and adoptive parents had criminal histories. Results showed a significant relationship between biological parents’ criminal convictions and criminal convictions in their adopted-away children. That is, those whose biological parents were criminal were more likely to commit crimes themselves as adults. In addition, the more crimes the biological parent had committed, the higher the rate of criminality in the adopted-away offspring. Surprisingly, in this and at least two other adoption studies, no evidence was found for heritability of violent offending. This suggests that while violent and nonviolent forms of antisocial behavior have much in common, they may differ in that heritable influences may affect the latter, but not the former.

The Brain

Blair et. al (1999) found that the fundamental dysfunction lies within the amygdala, a small almond-shaped structure that plays a critical role in processing emotion and mediating fear. Using PET scanning, Blair has shown that activation of the amygdala in normal volunteers is involved in responding to the sadness and anger of others, and he hypothesizes that amygdala dysfunction could explain the lack of fear and empathy in psychopaths. Blair points out, as the orbitofrontal cortex, which does the ‘thinking’, and the amygdala, which does the ‘feeling’, is highly interconnected.