Some online dating sites attempt to predict attraction based on qualities like whether people prefer scuba diving to shopping, or reading to running, or whether they tend to be shy or more outgoing. But social science studies have found that such a priori predictors aren't very accurate at all, and that the best prognosticators of how people will get along come from the encounters between them. Stronger predictors of possible romance include the tenor of their conversations, the subject of their discussions, or what they choose to do together.