 Expressions of happiness become more intentional with age, with young children interrupting their actions to smile or express happiness to nearby adults at 8–10 months of age, and with markedly different kinds of smiles (e.g., grin, muted smile, mouth open smile) developing at 10 to 12 months of age.Between 18–24 months, children begin to acquire a sense of self.This gives rise to the onset of self-conscious emotions (e.g., shame, embarrassment, guilt, pride) around that same age, which are considered more complex in nature than basic emotions such as happiness, anger, fear, or disgust.