1.1 Understanding How and Why

The science of human development seeks to understand how and why people—all groups of people, all over the world, of every age—change over time. The goal is to help all 7 billion people on Earth fulfill their potential. This science is one way to reach that goal.

Developmentalists recognize that growth over the life span is multidirectional, multi-contextual, multicultural, multidisciplinary, and plastic, five terms that will be explained soon. First we need to emphasize that developmental study is a science. It depends on theories, data, analysis, critical thinking, and sound methodology, just like every other science. All scientists ask questions and seek answers to figure out the “how and why.”

Science is especially necessary when the topic is human development: Lives depend on the answers. People disagree vehemently about what pregnant women should eat, whether babies should be left to cry, when children should be punished, under which circumstances adults should marry, or divorce, or retire, or die. Opinions are subjective, arising from emotions and culture. Scientists seek to progress from opinion to truth, from subjective to objective, from wishes to evidence.

The Scientific Method

FIGURE 1.1 Process, Not Proof Built Into the scientific method—in questions, hypotheses, tests, and replications—is a passion for possibilities, especially unexpected ones.

As you may realize, facts may be twisted, and applications sometimes spring from assumptions, not from data. To avoid unexamined opinions and to rein in personal biases, researchers follow five steps of the scientific method (see Figure 1.1):

1. Begin with curiosity. On the basis of theory, prior research, or a personal observation, pose a question.
2. Develop a hypothesis. Shape the question into a hypothesis, a specific prediction that can be tested.
3. Test the hypothesis. Design and conduct research to gather empirical evidence (data).

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4. Draw conclusions. Use the evidence to support or refute the hypothesis.
5. Report the results. Share the data, conclusions, and alternative explanations.

As you see, developmental scientists begin with curiosity and then seek the facts, drawing conclusions after careful research. Replication—repeating the procedures and methods of a study with different participants—is often a sixth and crucial step (Jasny et al., 2011). Are the findings from this replication study similar to the original study? Scientists study the reported procedures and results of other scientists. They read publications, attend conferences, send emails, and sometimes move from one nation to another to collaborate. Conclusions are revised, refined, and confirmed after replication.

The implications of those conclusions spread beyond science, involving religion, politics, and ethics. One of the most famous scientists of all time said, “Science without religion is lame; religion without science is blind” (Einstein, 1954/1994). Some of the politics and ethics of scientific research are discussed at the end of this chapter. Every chapter of this book, and every “Opposing Perspectives” feature, describes the interaction of empirical data with moral values.

The Nature–Nurture Controversy

A good example of the need for science concerns a great puzzle of development, the nature–nurture debate. Nature refers to the influence of the genes that people inherit. Nurture refers to environmental influences, beginning with the health and diet of the embryo’s mother and continuing a lifetime, including family, school, community, and society.

The nature–nurture debate has many other names, among them heredity–environment and maturation–learning. Under whatever name, the basic question is: How much of any characteristic, behaviour, or emotion is the result of genes and how much is the result of specific experiences? Some people are predisposed to believe that most traits are inborn, that children are innately good or bad, naturally innocent or evil. Other people stress nurture, crediting or blaming parents, or circumstances, or drugs, or food (as in “You are what you eat”).

Developmentalists have learned that neither belief by itself is accurate. The question is “how much,” not “which,” because both genes and the environment affect every characteristic: Nature always affects nurture, and then nurture affects nature. Some scientists think that even “how much” is misleading, as it implies that nature and nurture each contribute a fixed amount when actually their dynamic interaction is crucial (Gottlieb, 2007; Meaney, 2010; Spencer et al., 2009). I fainted at Caleb’s birth because of the interaction of at least seven factors (low blood sugar, lack of sleep, physical exertion, gender, age, relief, joy), all influenced by both nature and nurture, all combining to land me on the floor.

A VIEW FROM SCIENCE

Sudden Infant Death*

Coverage of every topic in this book is based on research that follows the scientific method. Here we present one topic, sudden infant death syndrome (SIDS), to illustrate. Every year until the mid-1990s, tens of thousands of 2- to 6-month-old infants died of SIDS (called crib death in North America, cot death in England, nameless but nonetheless tragic in many developing nations). Tiny babies smile at their caregivers, wave at rattles that their small fingers cannot yet grasp, go to sleep, but never wake up. For many years, as parents mourned, scientists asked why (step 1) and tested hypotheses (the cat? the quilt? unpasteurized honey? homicide? spoiled milk?) to no avail: Sudden infant death was a mystery.

Then a scientist named Susan Beal studied every SIDS death in South Australia, seeking factors that might be causes. She learned that some circumstances did not matter (such as birth order) and others increased the risk (such as maternal smoking and lambskin blankets).

A breakthrough came when Beal noticed an ethnic variation: Australian babies of Chinese descent died far less often of SIDS than did Australian babies of European descent. Genetic? Most experts thought so. But Beal’s scientific observation led her to note that Chinese babies slept on their backs, contrary to the Australian (as well as European and North American) custom of stomach-sleeping. She developed a new hypothesis (step 2): Sleeping position matters.

To test her hypothesis (step 3), Beal convinced a large group of non-Chinese parents to put their newborns to sleep on their backs. Almost none of the infants died suddenly. After several years of data, she drew a surprising conclusion (step 4): Back-sleeping protected against SIDS. Her published reports (step 5) (Beal, 1988) caught the attention of doctors in the Netherlands, where pediatricians for some time had been telling parents that babies should sleep on their stomachs. Two Dutch scientists (Engelberts & de Jong, 1990) recommended back-sleeping; thousands of parents took heed. SIDS was reduced in Holland by 40 percent in one year—a stunning replication (step 6).

Sleeping Safely Sudden infant death syndrome occurred too often in many nations before 1990, but not in Mongolia (shown here) or other Asian countries. The reason, as scientists hypothesized and later confirmed, is that Asian parents put their children “back to sleep.”

SEAN SPRAGUE/THE IMAGE WORKS

In Canada in 1993, the federal government and several public health organizations began recommending that parents place their babies on their backs to sleep. SIDS rates had been falling since the late 1980s, but after the government launched a formal “Back to Sleep” campaign in 1999, the rate of SIDS in Canada fell by 50 percent over the next five years. Researchers believe this significant reduction can be directly linked to the increase in the number of babies who were put to sleep on their backs, as well as to lower smoking rates among pregnant women.

OBSERVATION QUIZ

Back-sleeping babies sometimes squirm, making the blankets covering them come loose—another risk factor for SIDS. What detail makes that unlikely here?

The swaddling blanket is not only folded under the baby but is also tied in place.

Stomach-sleeping is a proven, replicated risk, but it is not the only one: SIDS still occurs. Beyond sleeping position, and factors such as cigarette smoke in the household and low birth weight, other risks include a brain-stem abnormality that produces too little serotonin (a neurotransmitter), soft blankets or pillows, and bed-sharing (when infants sleep in their parents’ beds) (Duncan et al., 2010; Ostfeld et al., 2010). In Canada, there is currently a higher incidence of SIDS among infants born prematurely and with low birth weight or those born to low-income or Aboriginal parents (Public Health Agency of Canada, 2011a). As with almost every development, a combination of nature and nurture produces the outcome.

*Each chapter includes a feature entitled A View From Science that is intended to help readers to understand the scientific process as well as to learn details of a topic of interest. For both reasons, don’t skip over these features.