Lifespan Development. Tara L. Kuther

as illustrated in Figure 1.7.

      As an example, contextual factors such as gravity, light, temperature, and moisture even influence how genes are expressed and therefore how individuals develop (Meaney, 2017). For instance, in some reptiles, such as crocodiles, sex is determined by the temperature in which the organism develops. Eggs incubated at one range of temperatures produce male crocodiles and at another temperature produce female crocodiles (Pezaro, Doody, & Thompson, 2017).

      Description

      Figure 1.7 Interaction of Genetic and Environmental Factors

      Development is influenced by the dynamic interplay of genetic and environmental factors. Genetic predispositions may influence how we experience environmental factors, and environmental factors may influence how genes are expressed.

      Source: The Role of Genetic and Environmental Factors in the Development of Schizophrenia by Jonathan Picker, PhD, Psychiatric Times, August 01, 2005.

      According to evolutionary developmental theory, genetic factors and biological predispositions interact with the physical and social environment to influence development, and Darwinian natural selection determines what genes and traits are passed on to the next generation (Bjorklund, 2018; Witherington & Lickliter, 2016). People are viewed as active in their development, influencing their contexts, responding to the demands for adaptation posed by their contexts, and constantly interacting with and adapting to the world around them. The relevance of both biological and contextual factors to human development is indisputable, and most developmental scientists appreciate the contributions of evolutionary developmental theory (DelGiudice, 2018; Frankenhuis & Tiokhin, 2018; Legare, Clegg, & Wen, 2018). The ways in which biology and context interact and their influence on development change over the course of the lifetime, as we will discuss throughout this book.

      Thinking in Context 1.3

      Maria and Fernando have just given birth to their first child, a healthy baby boy. Like most new parents, Maria and Fernando are nervous and overwhelmed with their new responsibilities. Of utmost importance to them is that the baby develop a strong and secure bond to them. They want their baby to feel loved and to love them.

      1 What advice would a psychoanalytic theorist give Maria and Fernando? Contrast psychoanalytic with behaviorist perspectives. How might a behaviorist theorist approach this question?

      2 How might an evolutionary developmental theorist explain bonding between parents and infants? What advice might an evolutionary developmental theorist give to Maria and Fernando?

      3 Considering bioecological systems theory, what microsystem and mesosystem factors influence the parent–child bond? What role might exosystem and macrosystem factors take?

Table 1.5

      The many theories of human development offer complementary and contrasting views of how we change throughout our lifetimes. Table 1.5 provides a comparison of theories of human development.

      Research in Human Development

      The many theories of lifespan human development differ in focus and explanation, but they all result from scientists’ attempts to organize observations of people at all ages. Developmental scientists conduct research to gather information and answer questions about how people grow and change over their lives. They devise theories to organize what they learn from research and to suggest new hypotheses to test in research studies. In turn, research findings are used to modify theories. By conducting multiple studies over time, developmental scientists refine their theories about lifespan human development and determine new questions to ask.

      The Scientific Method

      Researchers employ the scientific method, a process of posing and answering questions by making careful and systematic observations and gathering information. The scientific method provides an organized way of formulating questions, finding answers, and communicating research discoveries. Its basic steps are as follows:

      1 Identify the research question or problem to be studied and formulate the hypothesis, or proposed explanation, to be tested.

      2 Gather information to address the research question.

      3 Summarize the information gathered and determine whether the hypothesis is refuted, or shown to be false.

      4 Interpret the summarized information, consider the findings in light of prior research studies, and share findings with the scientific community and world at large.

      In practice, the scientific method usually does not proceed in such a straightforward, linear fashion. Frequently, research studies raise as many questions as they answer—and sometimes more. Unexpected findings can prompt new studies. For example, researchers may repeat an experiment (called a replication) to see whether the results are the same as previous ones. Sometimes analyses reveal flaws in data collection methods or research design, prompting a revised study. Experts may also disagree on the interpretation of a study. Researchers may then conduct new studies to test new hypotheses and shed more light on a given topic. For all of these reasons, scientists often say the scientific method is “messy.”

      Methods of Data Collection

      The basic challenge that scientists face in conducting research is determining what information is important and how to gather it. Scientists use the term data to refer to the information they collect. How can we gather data about children, adolescents, and adults? Should we simply talk with our participants? Watch them as they progress through their days? Hook them up to machines that measure physiological activity such as heart rate or brain waves? Developmental scientists use a variety of different methods, or measures, to collect information.

      Observational Measures

      Observational measures are methods that scientists use to collect and organize information based on watching and monitoring people’s behavior. Developmental scientists employ two types of observational measures: naturalistic observation and structured observation.

      Scientists who use naturalistic observation observe and record behavior in natural, real-world settings. For example, Coplan, Ooi, and Nocita (2015) studied peer interaction patterns in children by observing 9- to-12-year-old children in the schoolyard during recess and lunch. They recorded the children’s activity and interaction with peers and found that children who were consistently unengaged with peers tended to show high levels of problems, such as anxiety, depression, and loneliness, as reported by both the children and their mothers.

      This researcher is using a video camera to observe and record the facial expressions a newborn baby makes while it sleeps.

      Thierry Berrod, Mona Lisa Production / Science Source

      Sometimes the presence of an observer causes those being observed to behave in unnatural ways or ways that are not typical for them. This is known as participant reactivity, and it poses a challenge to gathering by naturalistic observation. One way of reducing the effect of observation is to conduct multiple observations so that the children get used to the observer and return to their normal behavior. Another promising method of minimizing participant reactivity is to use an electronically activated voice recorder (EAR) (Mehl, 2017). Participants carry the EAR as they go about their daily lives. The EAR captures segments of information over