3-1 How do theories advance psychological science?

In everyday conversation, we often use theory to mean “mere hunch.” Someone might, for example, discount evolution as “only a theory”—as if it were mere speculation. In science, a theory explains behaviors or events by offering ideas that organize what we have observed. By organizing isolated facts, a theory simplifies. By linking facts with deeper principles, a theory offers a useful summary. As we connect the observed dots, a coherent picture emerges.

A theory about the effects of sleep on memory, for example, helps us organize countless sleep-related observations into a short list of principles. Imagine that we observe over and over that people with good sleep habits tend to answer questions correctly in class, and they do well at test time. We might therefore theorize that sleep improves memory. So far so good: Our principle neatly summarizes a list of facts about the effects of a good night’s sleep on memory.

Yet no matter how reasonable a theory may sound—and it does seem reasonable to suggest that sleep could improve memory—we must put it to the test. A good theory produces testable predictions, called hypotheses. Such predictions specify what results (what behaviors or events) would support the theory and what results would disconfirm it. To test our theory about the effects of sleep on memory, our hypothesis might be that when sleep deprived, people will remember less from the day before. To test that hypothesis, we might assess how well people remember course materials they studied before a good night’s sleep, or before a shortened night’s sleep (FIGURE 3.1). The results will either confirm our theory or lead us to revise or reject it.

Our theories can bias our observations. Having theorized that better memory springs from more sleep, we may see what we expect: We may perceive sleepy people’s comments as less insightful. The urge to see what we expect is ever-present, both inside and outside the laboratory. According to the bipartisan U.S. Senate Select Committee on Intelligence (2004), preconceived expectations that Iraq had weapons of mass destruction led intelligence analysts to wrongly interpret ambiguous observations as confirming that theory (much as people’s views of climate change may influence their interpretation of local weather events). This theory-driven conclusion then led to the preemptive U.S. invasion of Iraq.

To avoid biases, psychologists report their research with precise operational definitions of procedures and concepts. Sleep deprived, for example, may be defined as “X hours less” than the person’s natural sleep. Using these carefully worded statements, others can replicate (repeat) the original observations with different participants, materials, and circumstances. The first study of hindsight bias (the tendency to believe, after learning an outcome, that one would have foreseen it) aroused psychologists’ curiosity. Now, after many successful replications with differing people and questions, we feel sure of the phenomenon’s power. Although a “mere replication” of someone else’s research seldom makes headline news, recent instances of fraudulent or hard-to-believe findings have sparked calls for more replications (Asendorff et al., 2013). Replication is confirmation. Replication enables scientific self-correction. One Association for Psychological Science journal now devotes a section to replications and 72 researchers are collaborating on a “reproducibility project” that aims to replicate a host of recent findings (Open Science Collaboration, 2012). So, replications are increasing, and so far, most “report similar findings to their original studies” (Makel et al., 2012).

27

In the end, our theory will be useful if it (1) organizes a range of self-reports and observations, and (2) implies predictions that anyone can use to check the theory or to derive practical applications. (Does people’s sleep predict their retention?) Eventually, our research may (3) stimulate further research that leads to a revised theory that better organizes and predicts what we know.

As we will see next, we can test our hypotheses and refine our theories using descriptive methods (which describe behaviors, often through case studies, surveys, or naturalistic observations), correlational methods (which associate different factors), and experimental methods (which manipulate factors to discover their effects). To think critically about popular psychology claims, we need to understand these methods and know what conclusions they allow.