Episodic Memory in Adult Age and Effects of Sibship Size and Birth Order: Longitudinal Data

Abstract

This study examined the effects of sibship size and birth order on episodic memory performance in adulthood and old age. Participants were 1,141 healthy individuals aged 35–80 years, who took part in a longitudinal project on age, health, and memory. Episodic memory measurements over a 5-year interval included tests of recognition (recognition of faces, family names, first names, and nouns) and tests of recall (free recall of sentences, free recall and cued recall of nouns, and recall of activities). Results showed significant effects for both recall and recognition, that is, the smaller the sibship size is for an individual and the earlier born, the better memory performance. These results demonstrate that the effects of sibship size and birth order previously shown in children and adolescents (Belmont and Marolla, Science 182:1096–1101, 1973; Zajonc and Markus, Psych Rev 82:74–88, 1975; Zajonc, Am Psychol 56:490–496, 2001) are robust over time and hold over a large adult range.