Infants and Children in Context. Tara L. Kuther

of use, self-report measures are not without challenges. Sometimes children give socially desirable answers: They respond in ways they would like themselves to be perceived or believe researchers desire. A fifth-grade student completing a survey about cheating, for example, might sometimes peek at other students’ tests, but she might choose survey answers that do not reflect this behavior. Her answers might instead match the person she aspires to be or the behavior she believes her teacher expects—that is, someone who does not cheat on exams. Self-report data, then, may not always reflect children’s understanding, attitudes, or behavior.

      Physiological Measures

      Physiological measures are increasingly used in developmental research because cognition, emotion, and behavior have physiological indicators. For example, when you are speaking in public, such as when you give a class presentation, do you feel your heart beat more rapidly or your palms grow sweaty? Increases in heart rate and perspiration are physiological measures of anxiety that might be measured by researchers. Other researchers might measure cortisol, a hormone triggered by the experience of stress (Simons, Cillessen, & de Weerth, 2017).

      Some researchers measure eye movements or pupil dilation as indicators of attention and interest. For example, researchers in one study examined infants’ pupil dilation to determine whether they detect and attend to an unusual sound (Wetzel, Buttelmann, Schieler, & Widmann, 2016). Another study examined older children’s eye movements to determine their attention to healthy and unhealthy foods depicted in a cartoon (Spielvogel, Matthes, Naderer, & Karsay, 2018). The children paid more attention to unhealthy foods than healthy foods, especially when the characters were shown interacting with and eating the unhealthy food.

      In recent decades, researchers have increasingly used physiological measures of brain activity to study human behavior. There are many ways of measuring brain activity, and each measure provides a different perspective, as noted in the Lives in Context feature. An advantage of physiological measures is that they do not rely on verbal reports and generally cannot be faked. A challenge to physiological measures is that, although physiological responses can be recorded, they may be difficult to interpret. For example, excitement and anger may both cause an increase in heart rate. Data collection methods are summarized in Table 1.4.

Table 1.4

      Lives in Context: Cultural Context

      Methods of Studying the Brain

      What parts of the brain are active when children solve problems or feel emotions? How does the brain change with development? Until recently, the brain was a mystery. Over the past hundred years, researchers have devised several ways of studying brain activity that have increased our understanding of how the brain functions and how it develops.

      The earliest instrument created to measure brain activity was the electroencephalogram, first used with humans in the 1920s (Collura, 1993). Electroencephalography (EEG) measures electrical activity patterns produced by the brain via electrodes placed on the scalp. Researchers study fluctuations in activity that occur when participants are presented with stimuli or when they sleep. EEG recordings measure electrical activity in the brain, but they do not provide information about the location of activity.

      Not until the invention of positron emission tomography (PET) in the early 1950s did researchers obtain the first glimpse of the inner workings of the brain (Portnow, Vaillancourt, & Okun, 2013). Researchers inject a small dose of radioactive material into the participant’s bloodstream and the PET scan measures its flow throughout the brain. The resulting images can illustrate what parts of the brain are active as participants view stimuli and solve problems. Developed in 1971, computerized tomography, known as the CT scan, produces X-ray images of brain structures that are combined to make a three-dimensional picture of the person’s brain, providing images of bone, brain vasculature, and tissue (Cierniak, 2011). Because both PET and CT scans rely on the use of radioactive material, these methods are generally only used for diagnosis rather than research.

      Commonly used for research, functional magnetic resonance imaging (fMRI) measures brain activity by monitoring changes in blood flow in the brain (Bandettini, 2012). Developed in the 1990s, MRI machines house a powerful magnet that uses radio waves to measure the blood oxygen level. Active areas of the brain require more oxygen-rich blood. Like PET scans, fMRI enables researchers to determine what parts of the brain are active as individuals complete cognitive tasks.

      Near-infrared spectroscopy (NIRS) involves directing infrared light into brain tissue and detecting its differential absorption in response to neural activity. Unlike fMRI, NIRS does not require the child to remain motionless (Yücel, Selb, Huppert, Franceschini, & Boas, 2017). The infant wears a cap with sensors and can move and interact with others during testing (McDonald & Perdue, 2018). NIRS, however, measures activity only on the outer part of the brain, the cortex, limiting its use somewhat.

      What Do You Think?

      1 If you were going to study the brain, which measure would you choose and why?

      2 Would you use the same measure for an infant and older child? Why or why not?

      3 Identify a research question that your measure might help you answer. What type of information would you obtain from your chosen measure? ●

      Research Designs

      Conducting research entails determining a question, deciding what information to collect, and choosing a research design—a technique for conducting the research study. Developmental scientists employ several types of designs.

      Case Study

      A case study is an in-depth examination of a single individual (or small group of individuals). It is conducted by gathering information from many sources, such as through observations, interviews, and conversations with family, friends, and others who know the individual. A case study may include samples or interpretations of a person’s writing, such as poetry or journal entries, artwork, and other creations. A case study provides a rich description of a person’s life and influences on his or her development. It is often employed to study individuals who have unique and unusual experiences, abilities, or disorders. Conclusions drawn from a case study may shed light on an individual’s development but may not be generalized or applied to others. Case studies can be a source of hypotheses to examine in large-scale research.

      Correlational Research

      Are children with high self-esteem more likely to excel at school? Are toddlers with working parents more aggressive? Do children who participate in athletic activities have a positive body image? All of these questions can be studied with correlational research, which permits researchers to examine relations among measured characteristics, behaviors, and events. For example, in one study, scientists examined the relationship between physical fitness and academic performance in middle school students and found that children with higher aerobic capacity scored higher on achievement tests than did children with poorer aerobic capacity (Bass, Brown, Laurson, & Coleman, 2013). Note that this correlation does not tell us why aerobic capacity was associated with academic achievement. Correlational research cannot answer this question because it simply describes relationships that exist among variables; it does not enable us to reach conclusions about the causes of those relationships. It is likely that other variables influence both a child’s aerobic ability and achievement (e.g., health), but correlation does not enable us to determine the causes for behavior—for that we need an experiment.

      Experimental Research

      Developmental scientists who seek to test hypotheses about causal relationships, such as whether media exposure influences behavior or whether hearing particular types of music influences mood, employ experimental