The scientific method illuminates and illustrates human development as nothing else does. Facts, hypotheses, and possibilities have all emerged that would not be known without science—and people of all ages are healthier, happier, and more capable than people of previous generations because of it.

For example, infectious diseases in children, illiteracy in adults, depression in late adulthood, and racism and sexism at every age are much less prevalent today than a century ago. Science deserves credit for all these advances. Even violent death is less likely, with scientific discoveries and universal education considered likely reasons (Pinker, 2011).

Developmental scientists have also discovered unexpected sources of harm. Video games, cigarettes, television, shift work, and asbestos are all less benign than people first thought. Although the benefits of science are many, so are the pitfalls. We now discuss three potential hazards: misinterpreting correlation, depending too heavily on numbers, and ignoring ethics.

Probably the most common mistake in interpreting research is confusing correlation with causation. A correlation exists between two variables if one variable is more—or less—likely to occur when the other does. A correlation is positive if both variables tend to increase together or decrease together, negative if one variable tends to increase while the other decreases, and zero if no connection is evident.

To illustrate: From birth to age 9, there is a positive correlation between age and height (children grow taller as they grow older), a negative correlation between age and napping (children nap less often as they grow older), and zero correlation between age and number of toes (children do not grow new toes with age). (Now try the quiz on correlation in Table 1.3.)

Positive; third variable: heat

Negative; third variable: age

Zero; each child must have a parent of each sex; no third variable

29

Many correlations are unexpected. For instance, first-born children are more likely to develop asthma than are later-born children, teenage girls have higher rates of mental health problems than do teenage boys, and newborns of immigrants weigh more than do newborns of nonimmigrants. All these surprising correlations are discussed later.

However, correlation is not causation. Just because two variables are correlated does not mean that one causes the other—even if it seems logical that it does. Correlation proves only that the variables may be connected. Indeed, sometimes two variables follow the same pattern but are not connected at all (see Visualizing Development on p. 31).

Many mistaken and even dangerous conclusions are drawn because people misunderstand correlation, as the following A View from Science explains.

The most important caution for all scientists, especially for those studying humans, is to uphold ethical standards in their research. Each academic discipline and every professional society involved in the study of human development has a code of ethics (a set of moral principles) delineating specific practices to protect the integrity of research.

Ethical standards and codes are increasingly stringent. In the United States, most educational and medical institutions have an Institutional Review Board (IRB), a group that permits only research that follows certain guidelines. IRBs often slow down scientific study, but they are necessary: Some research conducted more than 50 years ago, before IRBs were established, was clearly unethical, especially when the participants were children, members of minority groups, prisoners, or animals (Blum, 2002; Washington, 2006).

31

32

Scientists—and everyone else—are horrified to learn about the Tuskegee study that did not treat people who had syphilis or the Little Albert research that taught an infant to fear white furry things. Details of these studies, and several others, continue to haunt current scientists, who follow many safeguards to make sure such moral lapses never happen again.

The most important safeguards are those that ensure no one is harmed by the study. Participation must be voluntary and confidential. This entails the informed consent of the participants—that is, they must understand and agree to the research procedures, knowing what risks are involved. For children, consent must be obtained from the parents as well, and the children must be allowed to end their participation at any time.

When the study is over, the participants must be “debriefed”—told what the study was about and what the results were.

Scientists are obligated to “promote accuracy, honesty, and truthfulness” (American Psychological Association, 2010) in their methods and conclusions.

Deliberate falsification is unusual. When it does occur, it leads to ostracism from the scientific community, dismissal from a teaching or research position, and, sometimes, criminal prosecution. This occurred recently with Diederik Stapel, a Dutch social psychologist. He created data that was not actually collected. Unfortunately, he is one of several prominent scientists, in both the physical and the social sciences, who have committed fraud. Almost always, other scientists are the first to notice the deception and sound the alarm (W. Stroebe et al., 2012).

Another obvious breach of ethics is to “cook” the data, or distort one’s findings, in order to make a particular conclusion seem to be the only reasonable one. This is not as rare as it should be. Tenure, promotion, and funding all encourage scientists to publish, and publishers seek remarkable findings. Awareness of this danger is leading to increased calls for replication (Carpenter, 2012).

Scientists are rewarded for publishing surprising results. When a hypothesis is not confirmed, that may lead to the “file drawer problem”; that is, a study is filed away and never published because the results are not exciting.

Ethical standards cannot be taken for granted. As stressed in the beginning of this chapter, researchers, like all other humans, have strong opinions, and they expect research to confirm their opinions. Therefore, sometimes without even realizing it, they might try to achieve the results they want. As one team explains:

Our job as scientists is to discover truths about the world. We generate hypotheses, collect data, and examine whether or not the data are consistent with those hypotheses…. [But we] often lose sight of this goal, yielding to pressure to do whatever is justifiable to compile a set of studies we can publish. This is not driven by a willingness to deceive but by the self-serving interpretation of ambiguity….

[Simmons et al., 2011, pp. 1359, 1365]

33

Obviously, collaboration, replication, and transparency are essential ethical safeguards for all scientists.

Science can be a catalyst for social change, improving the lives of millions of people, as you will see often in this text. For example, the spread of preschool education, or the acceptance of children with disabilities, arose directly from research in child development.

In this chapter, changed attitudes about sexual orientation (page 22) and about marijuana (page 21) have followed new research on those topics. For both of these issues, and many others, the passions of people on opposite sides make evidence-based, unbiased studies especially needed—but these studies are not always available. For example, partly because marijuana has been illegal, two leaders fear that the current debates “are missing an essential piece of information: scientific evidence about the effects of marijuana on the adolescent brain” (DuPont & Lieberman, 2014, p. 557).

The ultimate purpose of the science of human development is to help “all kinds of people, everywhere, of every age” live satisfying and productive lives. Consider these questions:

The answer to all these questions is a resounding NO. Few funders are eager to support scientific studies of drug abuse, poverty, nonstandard families, or technology, partly because people have strong opinions and economic motives that may conflict with scientific findings and conclusions.

The next cohort of developmental scientists will build on what is known, mindful of what needs to be explored, answering the questions just posed and many more. Remember that the goal is to help all 7 billion people on Earth fulfill their potential. Much more needs to be learned. The rest of this book is a start.

34