Which technique of developmental researchers requires a significant expenditure of time as the researcher waits for the participants to get older?

The technique of developmental research which requires significant expenditure of time is called Longitudinal Studies.

Longitudial studies access changes by studying the same group of subjects  over an extended period of time - for months or even years. This form of research provides valuable information, but many factors can occur over time, like relocation or illness.

answer; empathy;

answer; the merit selection, also known as the missouri plan;