5 Steps to a 5 AP Psychology, 2010-2011 Edition (18 page)

Random assignment
—division of the sample into groups so that every individual has an equal chance of being put in any group or condition.

Confounding variables—
factors that cause differences between the experimental group and the control group other than the independent variable.

Operational definition
—a description of the specific procedure used to determine the presence of a variable.

Experimenter bias
—a phenomenon that occurs when a researcher’s expectations or preferences about the outcome of a study influence the results obtained.

Demand characteristics
—clues participants discover about the purpose of the study that suggest how they should respond.

Single-blind procedure
—research design in which participants don’t know whether they are in the experimental or control group.

Double-blind procedure
—research design in which neither the experimenter nor the participants know who is in the experimental group and who is in the control group.

Placebo
—a physical or psychological treatment given to the control group that resembles the treatment given to the experimental group, but contains no active ingredient.

Placebo effect
—a response to the belief that the independent variable will have an effect, rather than the actual effect of the independent variable, which can be a confounding variable.

Reliability
—consistency or repeatability of results.

Validity
—the extent to which an instrument measures or predicts what it is supposed to measure or predict.

Statistics
—a field that involves the analysis of numerical data about representative samples of populations.

•
Descriptive statistics
—numbers that summarize a set of research data obtained from a sample.

•
Frequency distribution
—an orderly arrangement of scores indicating the frequency of each score or group of scores.

•
Central tendency
—average or most typical scores of a set of research data or distribution.

mode
—most frequently occurring score in a set of research data (“quick and dirty”).

median
—the middle score when a set of data is ordered by size.

mean
—the arithmetic average of a set of scores.

•
Variability
—the spread or dispersion of a set of research data or distribution.

Range
—the difference between the largest score and the smallest score (“quick and dirty”).

Standard deviation (SD)
—measures the average difference between each score and the mean of the data set.

•
Normal distribution
—bell-shaped curve that represents data about how lots of human characteristics are dispersed in the population.

•
Percentile score
—the percentage of scores at or below a particular score.

•
Correlation coefficient (
r
)—a statistical measure of the degree of relatedness or association between two sets of data that ranges from −1 to +1.

•
Inferential statistics
—statistics that are used to interpret data and draw conclusions.

•
Statistical significance (
p
)
—the condition that exists when the probability that the observed findings are due to chance is less than 1 in 20 (
p
< .05) according to some psychologists, or less than 1 in 100 (
p
< .01) according to those with more stringent standards.

•
Ethical guidelines
—suggested rules for acting responsibly and morally when conducting research or in clinical practice.

IN THIS CHAPTER

Summary:
As you read this page, lots of things are going through your mind. Your mind is what your brain does, according to many psychologists. The relationships of behavior, the mind, and the nervous system, especially the brain, have become increasingly clear as improvements in technology have enabled scientists to make better observations. In all areas of anatomy and physiology, structure is related to function. Specialized structures throughout your body enable regulatory function at all levels of organization from your neurotransmitter molecules to your nervous and endocrine systems.

Neuropsychologists
explore the relationships between brain/nervous systems and behavior. Neuropsychologists are also called biological psychologists or biopsychologists, behavioral geneticists, physiological psychologists, and behavioral neuroscientists.

This chapter focuses on what we know about our nervous system and all of its parts at different levels of organization, and the tools that have enabled us to learn about them.

Key Ideas

Techniques to learn about structure and function

Nervous system organization

Brain structure and function

Neuron structure and functions

Endocrine system structure and function

Evolution and behavior

Genetics and behavior

As technology has improved, scientists have used a wide range of techniques to learn about brain and neural function. Over 150 years ago, studying patients with brain damage linked loss of structure with loss of function. Phineas Gage was the level-headed, calm foreman of a railroad crew (1848) until an explosion hurled an iron rod through his head. After the injury severed the connections between his limbic system and frontal cortex, Gage became hostile, impulsive, and unable to control his emotions or his obscene language. Observed at autopsy, his loss of tissue (where the limbic system is connected to the frontal lobes) revealed the relationship between frontal lobes and control of emotional behavior. In another case, Paul Broca (1861) performed an autopsy on the brain of a patient, nicknamed Tan, who had lost the capacity to speak although his mouth and vocal cords weren’t damaged and he could still understand language. Tan’s brain showed deterioration of part of the frontal lobe of the left cerebral hemisphere, as did the brains of several similar cases. This connected destruction of the part of the left frontal lobe known as
Broca’s area
to loss of the ability to speak, known as expressive
aphasia
. Carl Wernicke similarly found another brain area involved in understanding language in the left temporal lobe. Destruction of
Wernicke’s area
results in loss of the ability to comprehend written and spoken language, known as receptive
aphasia
.