If your eyes wrinkle when you smile or frown, you appear more sincere. Researchers have shown that our brains are pre-wired to perceive wrinkles around the eyes as conveying more intense and more sincere emotions. This eye-wrinkle feature, called the Duchenne marker, occurs across multiple facial expressions, including smiles, expressions associated with pain, and -- as found by these researchers -- expressions of sadness. Source 7h.