AP Psychology Notes

Unit 0: Science Practices

This unit introduces psychological perspectives and research methods used to gather data about human thinking and behavior. The content is located in the history and research methods chapters of AP Psychology textbooks. Research methods are crucial throughout the curriculum. The AP test requires applying research methods to multiple-choice and free-response questions from each unit.

History of Psychology

This chapter covers psychological perspectives.

Psychological Perspectives

Contemporary psychologists view human thought and behavior from various perspectives, categorized into eight broad categories.

Humanist Perspective

Humanists like Abraham Maslow (1908-1970) and Carl Rogers (1902-1987) emphasize individual choice and free will, contrasting with deterministic behaviorists who believe behaviors are caused by past conditioning. Humanists believe choices are guided by physiological, emotional, or spiritual needs. For example, an introverted person may limit social contact to satisfy social needs with close friends rather than large groups. Humanistic theories are hard to test scientifically and are sometimes seen as historical rather than current. However, therapists find humanistic ideas useful in helping clients overcome obstacles.

Psychodynamic Perspective

The psychodynamic perspective remains relevant, albeit controversial. It posits that the unconscious mind, which is beyond conscious control or access, significantly influences thought and action. Psychoanalysts explore impulses or memories repressed into the unconscious through dream analysis, word association, and psychoanalytic therapy. For instance, an introverted person might avoid social situations due to a repressed memory of childhood trauma involving social embarrassment or anxiety.

Biopsychology (or Neuroscience) Perspective

Biopsychologists explain human thought and behavior in terms of biological processes, such as genes, hormones, and neurotransmitters in the brain. For example, extroversion might be attributed to inherited genes and their impact on neurotransmitter abundance. Biopsychology is a rapidly advancing field, with some suggesting psychology may become a branch of biology.

Evolutionary (or Darwinian) Perspective

Evolutionary psychologists, or sociobiologists, examine human thoughts and actions through the lens of natural selection. Traits advantageous for survival are passed down. Based on Charles Darwin's (1809-1882) theory, extroversion could be seen as a survival advantage, where outgoing individuals make friends and allies, improving their survival chances and the likelihood of passing on the extroverted trait. This perspective is similar to biopsychology.

Behavioral Perspective

Behaviorists explain thought and behavior through conditioning, focusing on observable behaviors and responses to stimuli. Extroversion may be explained by rewards and punishments for being outgoing or withdrawing. Behaviorists examine environmental conditions causing extroverted responses.

Cognitive Perspective

Cognitive psychologists study thought and behavior by examining how we interpret, process, and remember environmental events. The rules used to view the world are crucial. Jean Piaget's (1896-1980) cognitive developmental theory explains how cognitions develop in stages. An extroverted person might interpret social situations as important for getting to know others or for personal life improvement. Cognitive psychologists believe extroversion stems from seeing the world in a way that makes being outgoing logical.

Social-Cultural (or Sociocultural) Perspective

Social-cultural psychologists study how thoughts and behaviors vary across cultures, emphasizing cultural influence. Extroversion is explained by examining cultural rules about social interaction, such as personal space during conversation, touching frequency, and the value placed on group versus individual identity.

Biopsychosocial Perspective

This perspective recognizes that human thinking and behavior result from biological, psychological, and social factors. It views other perspectives as too focused on specific influences and reductionistic. It explains extroversion through a combination of genetic tendencies (similar to biopsychological explanations), conditioning toward extroverted behavior, and social pressures like conformity.

Summary

Psychologists may agree that each perspective offers valid explanations depending on the situation, an approach called eclectic. This view claims that no single perspective has all the answers. Psychologists use different perspectives based on which best fits the explanation. Future perspectives may combine or new ones may emerge with continued research.

Research Methods

This chapter covers experimental and correlational methods, naturalistic observation, and case studies.

Key Terms

Key terms include:

  • Hindsight bias
  • Confirmation bias
  • Overconfidence
  • Quantitative research
  • Qualitative research
  • Hypothesis
  • Dependent variable
  • Independent variable
  • Falsifiable
  • Operational definitions
  • Replicated
  • Sample
  • Population
  • Representative sample
  • Random sampling
  • Convenience sampling
  • Generalize
  • Stratified sampling
  • Confounding variables
  • Random assignment
  • Experimenter bias
  • Double-blind study
  • Single-blind study
  • Social desirability bias
  • Experimental group
  • Control group
  • Placebo method
  • Placebo effect
  • Positive correlation
  • Negative correlation
  • Study
  • Likert scales
  • Directionality problem
  • Third variable
  • Naturalistic observation
  • Structured interview
  • Case study

Overview

Psychology is a science based on research. Intuition can be misleading, leading to hindsight bias—the feeling of knowing something all along after it occurs. Scientific research aims to predict events in advance. Research is also important because people exhibit confirmation bias, favoring information confirming existing beliefs, and overconfidence. Understanding research methods is crucial to psychology, emphasized more in the updated AP exam.

Applied vs. Basic Research

Research can be applied or basic. Applied research solves practical problems, such as comparing teaching methods or testing smoking cessation programs. Basic research explores questions of interest without immediate real-world applications, such as how attitudes are formed or how intelligence is defined across cultures.

Quantitative vs. Qualitative Research

Research can be quantitative, using numerical measures, or qualitative, using complex textual responses to find key themes.

Hypotheses and Variables

Most psychological research is guided by hypotheses, which express relationships between variables. Variables can vary among participants, such as religion, stress level, and height. An experimental hypothesis states that the dependent variable depends on the independent variable. For example, the hypothesis that violent television makes people more aggressive suggests that watching violent television (independent variable) changes behavior (dependent variable). Researchers manipulate the independent variable and measure the dependent variable. Hypotheses stem from theories, which explain phenomena and allow generating testable hypotheses. Hypotheses must be falsifiable, meaning data could disprove them.

Operational Definitions

Researchers must define variables operationally, explaining how they will be measured. For example, what programs are violent, and what behaviors are aggressive? Operationalization impacts the validity and reliability of research.

Validity and Reliability

Good research is valid (accurate) and reliable (consistent). Validity means the research measures what it intends to measure. Reliability means the research can be replicated with similar results.

Sampling

Sampling involves selecting participants for a study from a population. The goal is a representative sample, reflecting the larger population. Using only one's own psychology students is not representative. Random sampling, where every population member has an equal chance of selection, increases representativeness and generalizability. Using one's own students is convenience sampling.

Random Sampling

Psychologists use the term "random" precisely. Approaching people in front of a library may not be truly random. Random selection uses computers, random number tables, or drawing names from a hat.

Random sampling maximizes the chance that the sample will represent the population from which it was drawn and allows researchers to draw generalizations about the population based on their findings about the sample.

Stratified Sampling

A large sample is more likely to represent the population, but time and money can be limiting factors. Statistics determine the appropriate sample size. Stratified sampling ensures the sample represents the population based on specific criteria. For instance, representing racial groups proportionally. In a school of 1,000 students, with 500 white, 300 Black, and 200 Latino students, a sample of 100 should have 50 white, 30 Black, and 20 Latino students. This can be achieved by dividing potential participants by racial group and randomly selecting a subsample from each.

Experimental Method

Experiments can be laboratory (highly controlled) or field (realistic). The preferred method is the experiment because it can show causal relationships by manipulating the independent variable and controlling for confounding variables—differences between experimental and control conditions (other than the independent variable) that could affect the dependent variable. Random assignment to conditions and control methods eliminate confounding variables.

Random Assignment

Students often equate all research with experiments. As described in the text, many kinds of research can be conducted, but only experiments can identify cause and effect relationships.

Assignment

Assignment puts participants into experimental or control groups. Random assignment ensures each participant has an equal chance of being in either group, limiting participant-relevant confounding variables. Allowing participants to choose groups would likely result in dissimilar groups. Random assignment controls for participant-relevant variables.

Random assignment controls for participant-relevant confounding variables. Students sometimes confuse random assignment and random sampling. Although both involve randomization, sampling is the process of choosing the research participants from the population, and it happens before assignment. Assignment is the process of dividing participants into groups (for example, experimental and control), and it cannot be done until after you have identified the sample.

Ensuring Equivalent Groups

Differences between groups refer to group averages. A single, very aggressive subject will not throw off the results of the entire group. The idea behind random assignment is that, in general, the groups will be equivalent. To ensure experimental and control groups are equivalent on criteria like sex, IQ, or age, group matching can be used. The sample is divided into subgroups (e.g., males and females), and then half of each subgroup is randomly assigned to each condition.

Situation-Relevant Confounding Variables

Situation-relevant confounding variables can also affect an experiment. The situations that the different groups experience must also be equivalent except for the differences produced by the independent variable. If the experimental group watches violent television in a large lecture hall while the control group watches other programs in a small classroom, their situations are not equivalent. Making the environments into which the two groups are placed as similar as possible controls for situation-relevant confounding variables.

Experimenter Bias

Experimenter bias, an unconscious tendency for researchers to treat groups differently to confirm their hypothesis, is a situation-relevant variable. It can be eliminated by a double-blind procedure, where neither participants nor researchers can affect the outcome. A single-blind study, where only participants are unaware of their group assignment, minimizes demand characteristics and response bias. Demand characteristics are cues about the study's purpose that participants use to respond appropriately. Response/subject bias is the tendency to behave in certain ways. Social desirability bias involves giving answers that reflect well on oneself.

Experimental and Control Groups

Experiments have an experimental group (receiving the independent variable treatment) and a control group (receiving no treatment), serving as a comparison. Without a control group, determining if changes are due to the treatment or other factors is impossible. The Hawthorne effect shows that merely selecting a group affects its performance, irrespective of treatment. The placebo method involves giving the control group an inert substance, separating the physiological effects of a drug from the psychological effects of believing one took a drug (the placebo effect).

Counterbalancing

Sometimes using participants as their owns control group is possible, a procedure known as counterbalancing. For instance, if I wanted to see how frustration affected performance on an IQ test, I could have my participants engage in a task unlikely to cause frustration, then test their IQ, and then give them a frustrating task and test their IQs again. However, this procedure creates the possibility of order effects. This problem can be eliminated by using counterbalancing. I can counterbalance by having half the participants do the frustrating task first and half the participants do the not-frustrating task first and then switching.

Correlational Method

A correlation expresses a relationship between two variables without ascribing cause. Correlations can be positive (one predicts the presence of the other) or negative (one predicts the absence of the other).

Ex Post Facto Study

Sometimes psychologists elect not to use the experimental method. In some cases, testing a hypothesis with an experiment is impossible. If an experiment is impossible, an ex post facto (quasi-experimental) study can be done.

Survey Method

An even more popular research design is the survey method, which uses surveys. Items used on surveys can be Likert scales, which pose a statement and ask people to express their level of agreement/disagreement with the statement.

Understanding Limitations

The original hypothesis, that watching violent television programs makes people more aggressive, cannot be tested using the survey method, because only an experiment can reveal a cause-effect relationship. It may be that watching violent television causes aggression, but it is also possible that aggressive people are drawn to watch violent television. The inability to tell which of the variables came first (also known as temporal precedence) is called the directionality problem. It is also possible that a third variable―for instance, a genetic predisposition-causes both the love of violent television and one's aggressive behavior. In this case, there is no real relationship between the two variables being studied at all, and the correlation is known as a spurious (false) correlation.

Confounding Variables

Using the survey method means that one cannot control participant-relevant confounding variables. Controlling situation-relevant confounding variables using the survey method is possible (by bringing all the participants to one place at one time to fill out the survey), it is rarely done. Obtaining a random sample when one sends out a survey is difficult because relatively few people will send it back (low response rate), and these people are unlikely to make up a representative sample.

Naturalistic Observation

Researchers sometimes observe participants unobtrusively in their natural habitats to gain a realistic view of behavior. This is called naturalistic observation. Control is sacrificed for realism.

Qualitative Methods

Surveys can be open-ended, yielding qualitative data. Interviews, either one-on-one or in focus groups, also gather qualitative data. Interviews range from structured (fixed questions) to unstructured (allowing interviewer flexibility). Case studies provide a full, detailed picture of one participant or a small group, often used by clinical psychologists. Findings from case studies cannot be generalized to a larger population.

Statistics

This chapter focuses on descriptive and inferential statistics, correlations, and APA ethical guidelines related to data analysis.

Key Terms

Key terms include:

  • Central tendency
  • Mean
  • Median
  • Mode
  • Bimodal
  • Positively skewed
  • Negatively skewed
  • Range
  • Variance
  • Standard deviation
  • Normal curve
  • Percentiles
  • Correlation
  • Correlation coefficient
  • Scatterplot
  • Statistically significant
  • Effect size
  • Replication
  • Meta-analysis
  • Peer review
  • No coercion
  • Informed consent
  • Deception
  • Informed assent
  • Confidentiality
  • Risk
  • Protection from harm
  • Debriefing

Overview

Statistics are crucial for understanding and making inferences based on numerical data in psychological research. Understanding statistical terms and processes and testing oneself is important.

Descriptive Statistics

Descriptive statistics describe a data set. A frequency distribution summarizes data (e.g., the number of students with dogs, cats, etc.). Findings can be graphed using frequency polygons (line graphs) or histograms (bar graphs). The y-axis represents frequency, and the x-axis represents what is being graphed.

Measures of Central Tendency

Measures of central tendency mark the center of a distribution. The mean is the average, calculated by summing scores and dividing by the number of scores. The median is the central score when scores are ordered ascendingly or descendingly. If there are an odd number of scores, find the middle one. If the distribution contains an even number of scores, the median is the average of the middle two scores. The mode is the most frequent score; a distribution can be bimodal if two scores appear equally and more frequently than others.

Impact of Outliers

The mean is the most used measure of central tendency, but its accuracy can be distorted by extreme scores or outliers. Outliers skew distributions. In such cases, the median is a better measure. Unless a distribution is symmetrical, it is skewed. When a distribution includes an extreme score (or group of scores) that is very high, as in the car example above, the distribution is said to be positively skewed. When the skew is caused by a particularly low score (or group of scores), the distribution is negatively skewed. In a positively skewed distribution, the mean is higher than the median vice versa for a negatively skewed distribution.

Measures of Variability

Measures of variability depict the diversity of the distribution. These measures include the range, variance, and standard deviation. The range is the distance between the highest and lowest scores. Variance and standard deviation are closely related; standard deviation is the square root of the variance. Both relate to the average distance of scores from the mean. Higher values indicate more spread. Scores from different distributions can be compared using z-scores, which measure the distance from the mean in standard deviation units. Scores below the mean have negative z-scores, while scores above the mean have positive z-scores. In a normal distribution, approximately 68% of scores fall within one standard deviation of the mean, 95% within two, and almost 99% within three. Also, someone who scores at the 50th percentile has a z-score of 0, and someone who scores at the 98th percentile has an approximate z-score of +2.

Correlations

Correlations measure the relationship between two variables, being positive (presence of one predicts the other) or negative (presence of one predicts absence of the other). The strength of a correlation is computed by the correlation coefficient, ranging from -1 (perfect negative) to +1 (perfect positive), with 0 indicating no correlation. Correlations can be graphed on a scatterplot, with each axis representing a variable. The closer the points are to a straight line, the stronger the correlation.

Inferential Statistics

Inferential statistics determine if findings apply to the larger population. Samples must represent the population. The extent to which the sample differs from the population is known as sampling error. Inferential statistical tests, like t-tests, chi-square tests, and ANOVAs, yield a p-value, indicating the probability that the difference between groups is due to chance. A p-value of 0.05 or less indicates statistically significant results. The stronger the correlation and the larger the sample, the more likely the relationship will be statistically significant, which will be shown by a p-value of 0.05 or less. In addition to statistical significance, psychologists are interested in practical significance or how large an effect is; the goal is replicated findings that have both low p-values and high effect sizes.

Replication Crisis

In recent years, many areas of science, including psychology, have been experiencing a replication crisis. When we replicate a study, we conduct it again using the same methodology in an attempt to see if the results will be the same. Meta-analysis is a type of research that combines the results of many studies on the same topic in order to approximate an average effect. Prior to publication, psychology studies undergo peer review, a process by which a paper is read by several others in the field and the is author asked to make revisions in order to ensure high quality publications.

APA Ethical Guidelines

APA (American Psychological Association) has ethical guidelines that must be followed for human and animal research.

Ethical Review

Any type of academic research must first propose the study to the ethics board or institutional review board (IRB) at the institution. The IRB reviews research proposals for ethical violations and/or procedural errors. This board ultimately gives researchers permission to go ahead with the research or requires them to revise their procedures.

Animal Research

Ethical psychological studies using animals must meet the following requirements:

  • The research must have a clear scientific purpose.
  • The research must answer a specific, important scientific question.
  • Animals chosen must be best suited to answer the question at hand.
  • Researchers must care for and house animals in a humane way.
  • Researchers must acquire animal subjects legally. Animals must be purchased from accredited companies. If wild animals must be used, they need to be trapped in a humane manner.
  • Researchers must design experimental procedures that employ the least amount of suffering feasible.
Human Research

Research involving human subjects must meet the following standards:

  • No coercion-Participation should be voluntary.
  • Informed consent―Participants must know that they are involved in research and give their consent. If the participants are deceived in any way about the nature of the study, the deception must not be so extreme as to invalidate the informed consent, and it is ethically preferable to keep deception to a minimum. Only adults can consent to be in research; minors should be asked to assent (informed assent) and may also be asked to obtain the consent of their parent or guardian.
  • Confidentiality (or anonymity)-Participants' privacy must be protected. Their identities and actions must not be revealed by the researcher. Participants have anonymity when the researchers do not collect any data that enable the researchers to match a person's responses with his or her name. In some cases, such as interview studies, a researcher cannot promise anonymity but instead guarantees confidentiality, which means the researcher will not identify the source of any of the data.
  • Risk-Participants cannot be placed at significant mental or physical risk; they must have protection from harm. Typically, it is considered permissible for participants to experience temporary discomfort or stress. However, activities that might cause someone long-term mental or physical harm must be avoided.
  • Debriefing―After the study, participants should be told the purpose of the study and provided with ways to contact the researchers about the results. When research involves deception, it is particularly important to conduct a thorough debriefing.