Take this true-or-false quiz to see just how much you know about what does (and doesn't) cause your dynamic duo to droop.

“If you don’t want your boobs to hit your knees by the time you’re 30, always wear a bra, even to bed,” Halle Berry recently told InStyle. But the star—who credits wearing a bra around the clock as the reason she sports such a perky pair—may be misinformed. Take this true-or-false quiz to see just how much you know about what does (and doesn't) cause your dynamic duo to droop.

Your breasts droop as you get older

TRUE. That’s due to stretching of the Cooper's ligaments, the connective tissue in your breasts that helps keep 'em up and looking perky. “Like all the tissue in your body, they’re made up of collagen and elastin, which break down as you age,” explains Dan Mills, MD, vice president of the American Society for Aesthetic Plastic Surgery. In addition, as you go through menopause, dense glandular tissue is replaced by fat that’s more likely to droop, he says.

Wearing a bra can prevent breasts from sagging

FALSE. We hate to break it to you, but contrary to what Berry maintains, nothing can prevent the girls from going south. “A bra will hold up your breasts to give you the shape and look you want, but it can’t prevent further sagging, which is caused by age and gravity,” says Dr. Mills. In fact, one French researcher even suggested last year that wearing a bra encourages sagging by weakening the breast's supporting tissue. The one exception: a supportive sports bra. Running or other high impact aerobic exercises cause boobs to bounce up and down, which over time can break down connective tissue. So sports bras do help in that department.

The right exercises can keep your breasts perky

FALSE. All the push-ups in the world can’t reduce the droop—since breasts are made up of fat, not muscle—and so technically there’s nothing to tighten and tone. But chest exercises can help improve the appearance of your pectoral area by strengthening surrounding ligaments, including Cooper’s ligaments, which in turn may make your girls look more lively, notes Anne Taylor, MD, a clinical assistant professor of plastic surgery at Ohio State University.

Breastfeeding can cause sagging

FALSE. A 2008 study published in the Aesthetic Surgery Journal concluded that breastfeeding isn't a risk factor for ptosis (that’s a fancy name for drooping). The real culprit? Pregnancy itself. (Weight gain during pregnancy can cause ligaments to stretch, which can lead to drooping later.) While you can’t avoid sagging completely, you can minimize it by making sure you stick to a relatively healthy weight gain when you’re pregnant, says Dr. Taylor.

Smoking and suntanning affect how your breasts look