Longitudinal Studies vs Cross Sectional Studies

Definition: Longtindiunal study is a a study of the same participants over a longer period of time

e.g. Bowlby/Kohlberg 

• High control over participant variables

- Many logitudinal studies use repeated measures where the same participants are studied on multiple occassions over the months/years the stuidy is running. This mean that participant variable such as gender or age differences will not affect the results because you are using the same participant. 

- This increases INTERNAL VALIDITY. Because there are no participant variables to affect the results because the same participant is being used. 

• Can allow researchers to separate the effects of nature from nurture

- Because same person = same genetics therefore any changes in behaviour are due to the environment.

- This allows a cause and effect relationship.

Definition: Longtindiunal study is a a study of the same participants over a longer period of time

e.g. Bowlby/Kohlberg

• Very time consuming and cost a lot

- Lowers external validity as the sample size may be small due to the cost of studying larger groups of participants 

• Attrition( When Participants drop out half way through) is a particular problem in longitudinal research. The real problem is that those whp tend to drop out more often share similar characteristics (e.g. those who are less motivated, or who aaare more unhappy) resulting in the sample which remains becoming unrepresentative lowering external validity.

Definition: This method can also be used to study differenced in behaviour between people of different ages (Like a longitduinal study but with differetn groups of people)

• STRENGTHS
• Much quicker thtn a longitudinal study therefore cheaoer
• No risk of attrition

• WEAKNESSES
• Participant Variables. The other differences between the participants may impact behaviour. Lowers internal vlidity. Participant variables could become confounding variables as they could have an impact on the DV. Therefore it will be dificult to establish a cause and effect relationship.
• Cohort Effects. When people are born/living at a particular time share similar experiences which are different from those living at other times. These cohort effects can affect cross-sectional studies lowering internal validity