1. Research methods in developmental psychology
   As in other research disciplines, developmental psychologists rely on the scientific method to evaluate predictions of specific theories or to determine the applicability of theory to real-world settings.
   1. Measuring attributes and behaviors
      When conducting research, scientists examine variables such as attributes and behaviors that may vary among and within individuals. Variables must be operationally defined, that is, precisely specified in measurable terms. Variables must demonstrate validity, that is, must actually measure what they were intended to measure. The measurement of a variable must also be reliable when administered repeatedly, and when recorded by several observers it should show inter-rater reliability.
   2. Methods of collecting data
      Scientists who use naturalistic observations do not manipulate variables directly but simply attempt to discern important relationships among variables of interest. A well-designed naturalistic observation will have operationally defined all relevant variables, avoided participant reactivity (the tendency of participants who know that they are being observed to alter their behavior), and minimized the effects of observer bias (the tendency of researchers to interpret the behaviors being measured as consistent with their research hypotheses).
      Structured observations are research situations in which the experimenter devises ways to elicit those behaviors of interest that normally would not be displayed consistently in a natural setting.
      With structured interviews, children are asked the same sequence of questions. The questionnaire is a standard set of items to which children provide written responses. The clinical method is a flexible, open-ended questioning technique that permits the researcher to follow a child's train of thought. Researchers must be careful, however, to avoid situations that prompt children to shade the truth in order to present themselves in the best possible light.
      When a large number of studies are available on the same topic and the results are inconsistent or in conflict, a meta-analysis can be conducted. With meta-analysis, the results of previously published research are statistically analyzed to assess whether the central variable in all of the studies has an important effect.
   3. Research designs
      The type of research design an experimenter chooses determines whether a variable will be manipulated (experimental design) or not (correlational design), whether many or only a few participants will be studied, and other features of the research process.
      Correlational studies look for systematic relationships among variables of interest. The direction and strength of the relationship between two variables is described with the statistical tool known as the correlation coefficient (r). The sign of the r indicates whether the variables change in the same direction (positive correlation) or in the opposite direction (negative correlation). The value of r, which ranges from 1 to 1, indicates the strength of the relationship, with 0.0 signifying no relationship between variables and 1.0 indicating a perfect one-to-one relationship between variables. Since variables are not manipulated in correlational studies, it is not possible to determine cause-and-effect relationships. The strength of the correlational design lies in the ability to examine variables that can not be manipulated.
      The major strength of the experimental design is that it can isolate cause-and-effect relationships between variables. The variable suspected of being the cause of a behavior is called the independent variable. The dependent variable is the behavior being measured or the suspected outcome. Experimental studies are designed to allow the researcher to control for factors other than the independent variable that can influence the dependent variable. A common control procedure is random assignment of participants to different treatment groups, one of which is usually a control group that receives no treatment. In a field experiment, experimental manipulations are carried out in a natural setting, such as the child's home or school. In a quasi-experiment, the independent variable is not directly manipulated but occurs as a result of the participant's natural experiences.
      A case study, often in the form of a narrative, provides an in-depth description of an individual child. The single-case design provides an in-depth examination of one or a few children. It manipulates an independent variable and notes any change in behavior over time. Case studies can be particularly useful when children come from an unusual background or have an unusual ability.
   4. Strategies for assessing developmental change
      The developmental psychologist relies on two approaches to record changes in behavior that occur over time: the longitudinal study and the cross-sectional study.
      In the longitudinal study, the same sample of participants is repeatedly observed over time, typically over years. Longitudinal studies are subject to the age-history confound, in which historical changes can influence the variables the researchers are studying.
      In the cross-sectional study, children of different ages are observed or tested at the same point in time. Cross-sectional studies are subject to cohort effects, the generational differences among children of different ages that result from the cultural and historical climate in which they were reared.
      The sequential study is a compromise between the longitudinal and cross-sectional approaches. Groups of children at different ages are repeatedly observed or tested for only a few years.
   5. Cross-cultural studies of development
      Cross-cultural studies, which compare children from different cultural groups, are very useful in addressing whether certain behaviors or abilities are determined by biological or experiential factors. However, they pose unique difficulties for researchers who must be concerned about language and other differences. Cross-cultural studies also permit in-depth observations of behavior within the context of the particular meanings of importance to the culture, a benefit that can extend to understanding development in societies where there is considerable cultural diversity.
      
      
2. Ethical issues in developmental research
   The American Psychological Association has established guidelines for the use of human participants in psychological research. Participants must provide informed consent before participating in a study, have the right to decline or stop at any time, and be debriefed at the conclusion of the study if they were deceived about its true nature. The implementation of these guidelines with children is often difficult, because children may not understand the nature of the study and may be especially sensitive to the effects of participating in a research study.
   
   

Controversy: Should Researchers Reveal Information They Learn About Participants in Their Studies? When studying topics with important consequences, researchers may discover information about individuals that has significant consequences for their development. Researchers are expected to take action such as violating confidentiality if they believe that a child is at significant risk or is in jeopardy. However, such action may interfere with the conclusions that can be drawn from a study and raises further concerns about confidentiality. In some cases, such as if the researcher suspects child abuse, a legal obligation exists to enforce the principle of jeopardy.