Factorial invariance: A methodological issue in the study of psychological development

In this paper, I will discuss an issue which is believed to be crucial to the study of psychological and social development in adulthood and old age. This issue comes under the forbidding label of Factorial Invariance. Factorial Invariance is concerned with the interrelationships between variables in a given domain and whether such relationships are uniform under various conditions such as age differences. Specifically, if we wish to measure the same construct in the same way in a sample of old and young individuals, it is crucial that the relationships between that operational variable of interest and other variables in that domain be stable. If such relationships are not stable, it is quite possible that we are not measuring the same variable in the same way with the same test procedures or questionnaires in the old as in the young. The purpose of this paper is to further elaborate this idea.