RETRIEVAL PRACTICE Take a moment to answer each of these Learning Objective Questions (repeated here from within this section). Then click the 'show answer' button to check your answers. Research suggests that trying to answer these questions on your own will improve your long-term retention (McDaniel et al., 2009).

Psychological theories are explanations that apply an integrated set of principles to organize observations and generate hypotheses—predictions that can be used to check the theory or produce practical applications of it. By testing their hypotheses, researchers can confirm, reject, or revise their theories. To enable other researchers to replicate the studies, researchers report them using precise operational definitions of their procedures and concepts. If others achieve similar results, confidence in the conclusion will be greater.

Descriptive methods, which include case studies, naturalistic observations, and surveys, show us what can happen, and they may offer ideas for further study. The best basis for generalizing about a population is a representative sample; in a random sample, every person in the entire population being studied has an equal chance of participating. Descriptive methods cannot show cause and effect because researchers cannot control variables.

When we say two things are correlated, we are saying that they accompany each other in their movements. In a positive correlation, two factors increase or decrease together. In a negative correlation, one item increases as the other decreases. The strength of their relationship is expressed as a correlation coefficient, which ranges from +1.00 (a perfect positive correlation) through 0 (no correlation) to - 1.00 (a perfect negative correlation). Their relationship may be displayed in a scatterplot, in which each dot represents a value for the two variables.

Regression toward the mean is the tendency for extreme or unusual scores to fall back toward their average.

Correlations enable prediction because they show how two factors move together, either positively or negatively. A correlation can indicate the possibility of a cause-effect relationship, but it does not prove the direction of the influence, or whether an underlying third factor may explain the correlation.

To discover cause-effect relationships, psychologists conduct experiments, manipulating one or more factors of interest and controlling other factors. Using random assignment, they can minimize confounding variables, such as preexisting differences between the experimental group (exposed to the treatment) and the control group (given a placebo or different version of the treatment). The independent variable is the factor the experimenter manipulates to study its effect; the dependent variable is the factor the experimenter measures to discover any changes occurring in response to the manipulations. Studies may use a double-blind procedure to avoid the placebo effect.

Researchers intentionally create a controlled, artificial environment in the laboratory in order to test general theoretical principles. These general principles help explain everyday behaviors.

Some psychologists are primarily interested in animal behavior; others want to better understand the physiological and psychological processes shared by humans and other species. Government agencies have established standards for animal care and housing. Professional associations and funding agencies also establish guidelines for protecting animals’ well-being. The APA ethics code outlines standards for safeguarding human participants’ well-being, including obtaining their informed consent and debriefing them later.
     Psychologists’ values influence their choice of research topics, their theories and observations, their labels for behavior, and their professional advice. Applications of psychology’s principles have been used mainly in the service of humanity.