Ordering within the same food category as your friends brings greater happiness to restaurant-goers. Researchers found this peer pressure can overwhelm original desires for specific foods. People will try to avoid looking like the lone glutton or nutri-freak just to fit in. It's only true if people order out loud though. Researchers recommend ordering first because "the first person is the only one who truly gets what they want".
Positive Tip: Be a positive peer and order healthy dishes to encourage your friends when eating out.