These cards deliver different meanings, both on a personal and cultural level. Research suggests that birthday cards may be "indicators of societal attitudes towards aging, communication of love, and gender-based expressiveness. " For example, one study analyzing 150 birthday cards in 1981 found negative views on aging portrayed through humor. A 2017 study of online greeting cards found similar portrayals. Because of the ubiquity of the sentiments in cards, sociologist Dana Sawchuk recommended replicating this research with undergraduates as a form of active learning. Birthday cards can be written or printed for anyone, be it father, husband or a friend.