chris williams, hillary clinton, and beyonce are a few famous examples. the youngest child charming and popular. think whoopi goldberg, jon stewart, and steven colbert. bunch we're talking about jan. >> well, all i hear all day long at cool school is how great marsha is at this. marsha, marsha, marsha. >> now, sweetheart. >> donald trump is a middle child. so is kim kardashian. enough said. but is it true? does birth order really matter? >> birth order does not define who you are. there are other factors that determine your personality and intelligence level. >> a new study, one of the largest ever, put nearly half a million kids through a battery of personality and intelligence tests. and found that birth order made just a marginal difference. >> there's a very, very small association. it was.02. so that's almost zero. so how does that explain more than a century of anecdotal evidence? by a majority of u.s. presidents were first born sons. same for all of the actors who have ever played -- >> -- bond, james bond. >> how does it explain why so many younger kids go into comedy? or perhaps most telling, how does it explain why prince harry just seems c