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Developmental Psychology 101: Methods of Studying Development


The Developmental Psychology 101 series addresses the theories, periods, and implications of development in a human life from conception all the way through to the stage of adolescence. Developmental psychology is a field which is studied by psychology students and academic researchers; its purpose is to understand individuals based on the biological and psychological changes they experience throughout their lifespan. Development is defined as modifications that momentarily or permanently change an organism in the journey from conception to death (Cole et al., 2005). This 101 series of articles will refer to development from a psychological perspective, discussing its social, emotional, cognitive, and physical areas. Moreover, the debate of nature versus nurture will be discussed in the development of the following four stages of life: prenatal period, infancy, childhood, and adolescence.

The Developmental Psychology 101 series is divided into six chapters:

2. Developmental Psychology 101: Methods of Studying Development

3. Developmental Psychology 101: Prenatal Development and Birth

4. Developmental Psychology 101: Development in Infancy

5. Developmental Psychology 101: Development in Childhood

6. Developmental Psychology 101: Development in Adolescence

Developmental Psychology 101: Methods of Studying Development

No theory can be proven without scientific facts. The theories discussed in the previous article rely on well-developed methods of research when trying to answer questions in regard to development. This article strives to explain why the methods of research are different and how to use them in practice.

Before diving into the practical and organized world of research, one should understand the basic differences between the categories of research that are built on the goals of the researchers. Basic research has the goal of advancing the scientific knowledge of human development. Its results help solve practical problems, and it is mostly used to explore major theoretical issues (Cole et al., 2005, p. 30). Applied research “is designed to answer practical questions related to improving children’s lives and experiences” (Cole et al., 2005, p. 30). This category of research not only explores theories, but comes with the purpose of applying them in day-to-day life to bring real solutions to specific societal problems. Action research “is designed primarily to provide data that can be used in making social-policy decisions” (Coghlan & Jacobs, 2005 as cited in Cole et al., 2005, p. 30). An addition to basic and applied research, action research is meant to bring change at legal and governmental levels and has the purpose of adjusting opinions at a societal level.

Figure 1: Methods of Research (Minutes, 2019).

In order to fulfill the specific objective each researcher has when doing a study, these four criteria have been developed and are used in the qualitative judgment of studies. The first criterion is objectivity. This imposes that the gathering and analyzing of data should not be biased by the investigator’s opinions and perceptions (Cole et al., 2005, p. 31). Reliability, the second criterion, implies that the consistency of collected results is given by two aspects: investigators should get the same results every time they collect data under the same conditions while independent observers should be in agreement over the data collected at the same time, in the same conditions (Cole et al., 2005, p. 31). The replicability criterion says that in order to test if the hypothesis was truly proven or not by a study, independent investigators can replicate the study with the same criteria and procedures as the initial researcher. If the results are consistent in between studies, that is a good indicator that the study had qualitative results (Cole et al., 2005, p. 31). In science, validity means that the collected data reflects the studied phenomenon, hence the study measures what it is supposed to measure and the causal or correlative relationships have the implied effect on the data (Cole et al., 2005, p. 31). These are four of the most important aspects to be taken into consideration when beginning a psychological study.

Figure 2: Reliability and Validity in Psychology (Public Health Notes, 2018).

Methods of Studying Development

A variety of methods have been refined by researchers in the lifespan of this field that are still being implemented today. This article will focus on the three most widely used: naturalistic observation, experiment, and clinical interview.

Naturalistic observation is the most direct research method and implies watching the participants and recording what happens in certain conditions (Cole et al., 2005, p. 33). The observational study has the advantage of recording behaviors and observable and measurable actions directly. On the other hand, a big disadvantage is that people tend to behave differently when they are being watched, which might result in the study being scientifically invalid (Hoff-Ginsberg & Tardiff, 1955). Some other limitations that come up with this method are the investigator’s biases that would make them observe selectively and the information that is lost when the investigator does not manage to write everything down. A good way to combat these loses is recording while observing and analyzing the recorded material afterwards to fill in the gaps (Cole et al., 2005, p. 34).

Figure 3: Observing a child (Nursery World, 2022).

Experiments are used to study the cause-effect relationship of certain variables on others, which is how the independent variable causes a change on a dependent variable. Usually, the independent variable is defined as the treatment or intervention over what the investigator wishes to research, while the dependent variable frames a change in the behavior. To make sure that the change in the dependent variable is indeed caused by the modification of the independent one, researchers use different groups: the experimental group is exposed to the independent variable (or intervention), while the control group is not. If behavioral changes happen in both of these groups, with or without the intervention, it means that another variable caused the change to occur (Cole et al., 2005, p. 34).

The great advantage of using this method is that experiments can clearly separate variables and establish a causal or correlational relationship between them. Of course, this effect comes with the limitation of the fact that a controlled environment can distort the validity of the study and the results obtained. As it was already discussed, people tend to behave differently when observed, which might cause behavioral changes that would not normally occur if not observed. When the environment in which the children are tested differs a lot from their day-to-day environments, the experimental results are placed under questioning, as a generalization outside the clearly pre-set conditions cannot be made (Cole et al., 2005, p. 35).

Figure 4: The Marshmallow Experiment (Fypmoney, 2022).

The last method that is to be discussed is the clinical interview. In this frame of research, “questions are tailored to the individual, with each question depending on the answer to the previous one” (Cole et al., 2005, p. 35). The advantage of this method is that it can spot patterns in children's way of thinking and verbalizing of their thoughts. Jean Piaget is the figure that most established this method of research in his work focusing on the internal processes of the child. One can compare the differences in cognitive abilities of the children in the below example from Piaget’s series of interviews that focuses on this method of research.

Piaget: What is a dream? 11-year-old: It’s a thought. Piaget: What do you dream with? 11-year-old: With the head. (Piaget, 1929/1979, p. 39)

Piaget: When you are in bed and you dream, where is the dream? 5-year-old: In my bed, under the blanket. (Piaget, 1929/1979, p. 97)

This method allowed Piaget to develop his Constructivist theory that was described in the first article of this series. While holding interviews with children, Piaget managed to establish a thought pattern that each age would express, thus defining the boundaries of cognitive abilities of specific periods of time (Cole et al., 2005, p. 37).

Figure 5: Clinical Interview with a child (NDAA, 2021)

While researching children’s development, these three big methods of study often overlap: one might observe the recording of a clinical interview after the candidate finished an experiment and take notes on the process. This mix-and-match is often used to confirm the conclusions and to minimize the disadvantages of only using one method of research.

As it can be noticed, the methods of researching children’s development differ according to what the investigator wishes to study. If the cognitive aspects are targeted, then the clinical interview can be used. The experiment, however, should not be excluded, as the cognitive side of children’s development is vast, and it could be studied even on a computer through gamification. If the researcher wishes to study a behavior in its naturally occurring environment, the natural observation should be used as a method. Moreover, if a behavior should be changed through interventions, the experiment is the best way to go.

Figure 6: Emotional recognition experiment (Today's Parent, 2019).


Taking into consideration the learnings from this article, one could take forward a few concepts: research can either be basic, applied, or action research. A study of high quality, no matter if it uses the method of natural observation, experiment, or clinical interview, should prove objectivity, replicability, reliability and validity. Without these, the results of any study in the field of Developmental Psychology can be questioned. The results generated by this field of research help improve everyday actions of people that implement the new guidelines. Understanding how development works and how the environment as well as genetics affects children, researchers can offer solutions and ideas that can only improve parenting styles, thus improving the mental health of future adults.

Bibliographical References

Cole, M., Cole, S. R., & Lightfoot, C. (2005). The development of children, 7th Edition. Worth Publishers, New York.

Coghlan, D. & Jacobs, C. (2005). Kurt Lewin on reeducation: Foundations for action research. Journal of Applied Behavioral Science, 41(4), 444-457.

Hoff-Ginsberg, E. & Tardiff, T. (1955). Socioeconomic status and parenting. In M. H. Bornstein (Ed.), Handbook of parenting: Biology and ecology of parenting: Vol 2 (pp. 161-188). NJ: Lawrence Erlbaum Associates, Mahwah.

Piaget, J. (1929/1979). The language and thought of the child. Meridian Books, New York.

Visual Sources

Figure 1: Minutes. (2019). The Timeless Importance Of Research And Scholarship In Building Something Big. [Illustration]. Retrieved from:

Figure 2: Public Health Notes. (2018). 17 Differences between Validity and Reliability. [Illustration]. Retrieved from:

Figure 3: Nursery World. (2022). EYFS Best Practice - All about… observing progress. [Photo]. Retrieved from:

Figure 4: Fypmoney. (2022). Heard about “The Marshmallow Experiment”? [Photo]. Retrieved from:

Figure 5: NDAA. (2021). Best Practices in Forensic Interviewing and Working with Child Victims. [Photo]. Retrieved from:

Figure 6: Today's Parent. (2019). Does your kid need a therapist? [Photo]. Retrieved from:


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Raluca Reinerth

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