2.5 SUMMARY

• Empiricism is the belief that the best way to understand the world is to observe it firsthand. It is only in the last few centuries that empiricism has come into prominence.
• Empiricism is at the heart of the scientific method, which suggests that our theories about the world give rise to falsifiable hypotheses, and that we can thus make observations that test those hypotheses. The results of these tests can disprove our theories but cannot prove them.
• Observation doesn’t just mean “looking.” It requires a method. The methods of psychology are special because human beings are especially complex, variable, and reactive.

• Measurement involves defining a property in concrete terms and then constructing an instrument that can detect the things those terms specify.
• A good measure is valid (the things it measures are conceptually related to the property of interest), reliable (it produces the same measurement whenever it is used to measure the same thing), and powerful (it can detect changes in the dependent variable).
• Demand characteristics are features of a setting that suggest to people that they should behave in a particular way. Psychologists try to reduce or eliminate demand characteristics by making sure participants don’t know they are being observed, by measuring things that the participant can’t control, and by hiding their expectations from the participant.
• Observer bias is the tendency for observers to see what they expect to see or cause others to behave as they expect them to behave. Psychologists try to eliminate observer bias by making double-blind observations.

• To determine whether two variables are causally related, we must first determine whether they are related at all. This can be done by measuring each variable many times and then comparing the patterns of variation within each series of measurements. If the patterns are synchronized, then the variables are correlated.
• When we observe a naturally occurring correlation between two variables, we can’t conclude that they are causally related because there are an infinite number of third variables that might be causing them both.
• Experiments solve this third-variable problem. In experiments, we manipulate an independent variable, randomly assign participants to the experimental and control groups that this manipulation creates, and measure a dependent variable. These measurements are then compared across groups.
• An internally valid experiment establishes a causal relationship between variables as they were operationally defined and among the people who participated. An externally valid experiment mimics the real world.
• Thinking critically about evidence is difficult because people have a natural tendency to see what they expect to and to fail to consider what they don’t see.

• Institutional review boards ensure that scientific research upholds the principles of respect for persons, beneficence, and justice.
• Psychologists are obligated to get informed consent from participants, to not coerce participation, to protect participants from harm, to weigh benefits against risks, to avoid deception, and to keep information confidential.
• Psychologists are obligated to respect the rights of animals and treat them humanely. Most people are in favor of using animals in scientific research.
• Psychologists are obligated to tell the truth about their studies, to share credit appropriately, and to let others examine their data.