What may have originated as a sign of fertility has evolved into a device for wider-reaching social messaging about who you are. “Hair is the Swiss Army knife of beauty tools because it can convey so many things,” says Nancy Etcoff, Ph.D., psychologist at Harvard Medical School and author of “Survival of the Prettiest: The Science of Beauty.” Here are a few ways your hair speaks volumes:MORE: The Psychology of HairIt can symbolize a fresh startA flattering new cut and color offers a visual and mental do-over, which is why breakups and big birthdays are prime times for a chop. “When you’re open to meeting someone new after a breakup, you want to project a new level of confidence like you haven’t ‘had’ to project during your relationship,” says Art Markman, Ph.D., a psychology professor at the University of Texas at Austin and YouBeauty Psychology Advisor. Similarly, reaching a major age-marker, like turning 40 or 50 are times when women often want to make a new statement about who they are.MORE: Beauty Breakthroughs After a BreakupOr totally reboot your lifeHairstylist and YouBeauty Hair Advisor Guido likens a big change to a journey. “Every woman should chop her hair off once in her life, to try something totally new,” he says. It’s the sort of risky move that opens you up to changes and fulfillment in other parts of your life. “Even if you don’t like the initial results, as it grows back it will change and you might find a look that you would never have experienced,” he says.Hair attracts similar typesThe hairstyle you choose can act like a homing device to other like-minded people. “There’s a ‘birds of a feather effect’ with certain aspects of style that show our affiliation to a group,” says Etcoff. (Just look at the Real Housewives of Orange County…or the cast of Jersey Shore.)MORE: Breaking out of the Mold: Emma Stone Talks Beauty in ‘The Help’You can be a chameleonHair’s versatility allows you to change it to reflect who you are at any given moment. “You can start with a ponytail for the pre-school drop off, switch to a looser brushed-out look for lunch with your best girlfriend, and then run a hot iron through your ends for a more provocative look before your partner comes home,” says Guido. He encourages women to play with their hair to find different ways to wear it. “Just changing your part from side to center can give you a different look that you can use to express what you feel,” he says.MORE: The Best Haircut for Your Hair TypeIt lets you rage against the machine“A powerful style that goes against the conventional norm like punk hair or getting a pixie is a way of saying ‘don’t mess with me,’ and that you’re in control,” says Guido.QUIZ: How Healthy is Your Hair?