Speed dating and snap judgements
The advent of speed-dating and online matching services has led to a wealth of studies about dating behavior and what people look for in a potential partner. A study in the UK (link from Marginal Revolution) claims that women make up their minds about whether a man is a good match within 30 seconds of meeting!
As scary as that sounds (for a single guy like me), the skeptic in me says we should probably not jump to conclusions too quickly. The study was done on speed-daters which are clearly a self-selected group of people. People who speed date do so because they think they can form an impression of someone within a very short period of time. Men and women may also speed date for different reasons. For instance, women may want to sift through a large number of men to find that one perfect match while men may see it as a way to meet attractive women who would otherwise be unapproachable. Different motivations would therefore require different strategies.