As is speculated with other practices considered paraphilia, sexual imprinting may play a role in age-disparate relationships.
In some societies age-disparate relationships are seen as aberrant or even perverse.
They may seek the sexual vigor of the young, which partners of their own age group may no longer possess.
Assessment | Biopsychology | Comparative | Cognitive | Developmental | Language | Individual differences | Personality | Philosophy | Social | Methods | Statistics | Clinical | Educational | Industrial | Professional items | World psychology | Social psychology: Altruism · Attribution · Attitudes · Conformity · Discrimination · Groups · Interpersonal relations · Obedience · Prejudice · Norms · Perception · Index · Outline Significant age disparity in sexual relationships has been a feature of both heterosexual and same-sex couples in many cultures and societies.
The most common pattern in heterosexual couples is an older man with a younger woman.
This may be brought about as an arranged marriage, or either member may pursue and initiate the relationship in those societies that favor freer association.
Situations involving a younger male with an older female also exist, but are not as common.
Many arranged marriages have been age-disparate, with the husband being much older than the wife.
Mail-order brides have been frequently younger than their husbands.
In keeping with modern American mores, a folk formula (sometimes referred to as the Trophy Rule) seems to have evolved so as to compute correct disparities of age between older and younger partners, this being "divide by two and add seven", that is, the younger partner in a relationship should be at least seven years older than half the older partner's age, else the relationship is liable to be subject to moral disapprobation.
The United States Census Bureau's March 2000 statistics show that only 800,000 unmarried American couples are more than five years divergent in age, and 7 in 100 of women who have married more than once have a husband six or more years younger than they.
Age disparity in same-sex male relationships was even more historically common than age similarity in such relationships.
(Such relationships were practised in Ancient Greece, pre-Modern Japan, Melanesia, Islamic lands and Renaissance Italy.) Monarchs have traditionally exercised the freedom to choose younger spouses; Henry VIII, for instance, chose women far younger than himself as some of his wives, and a number of female monarchs have chosen younger consorts.
Age disparity in extreme cases may be seen as dysfunctional (a paraphilia) if such relationships are pursued to the exclusion of all others and to the detriment of the partners.