Cross-Sectional and Longitudinal approaches to the study of development
The study of development, also known as Developmental psychology is all about the study of change over time. It is about understanding the nature and processes that are involved in biological, social, cognitive and emotional changes. The main interest and focus of developmental psychology lies in childhood development from birth through to adolescence. However the main responsibility is to study change from infancy to old age. The goal is to establish a core understanding of changes and the processes that generate them.
Psychologists want to do more than simply describe, they want to understand the processes and causes of developmental change. They want to be able to explain changes in behaviour in order to be able to control or prevent it. In order to comprehend developmental change over time, psychologists have employed a number of research methods both experimental and non-experimental. One of the fundamental things that psychologists often examine is the change that occurs with age. That is to say performance at 2 or more age points. Psychologists have employed two approaches used for data collection so as to study change with age.
These approaches are Longitudinal and cross-sectional. The main feature of the longitudinal design is that it uses the same children at different age points. An example of this is Schaffer and Emerson’s (1964) longitudinal study of attachment. Using sixty infants, they examined their reaction to separation, from birth to eighteen months of age. This study enabled basic questions to be answered about the age at which attachment becomes intense. The longitudinal approach has lots of merits, particularly since it controls individual differences. However it is known for being time consuming.
That is to say in Schaffer and Emerson’s study of attachment, data was collected monthly. For example data is collected at 7 months followed by a one-month waiting period before data is collected once again at 8 months old. It has been known for the longitudinal approach to take years. An example of this could be the study of children’s memory at the age of five and ten. Data is collected when the child is aged five. Following this there is a five-year waiting period before data collection is complete at age ten. There are problems, however, regarding the longitudinal approach.
Because of the issue of time and the long waiting periods, participant drop out, also known as participant attrition, tends to be high. Participant attrition occurs for various reasons such as moving away, a lack of interest in the study or on a more serious note the death of a child. The problem of participant attrition raises the question of whether the remaining participants are representative of the original sample. It has been known for studies that start out with one hundred participants can end up with as little as thirty-five participants resulting in a participant attrition rate of 65%.