Using 20 levels of intensity, we measured children's thresholds to discriminate the six basic emotional expressions from neutral and their misidentification rates. Combined with the results of a previous study using the same method ("Journal of Experimental Child Psychology, 102" (2009) 503-521), the results indicate that by 5 years of age, children are adult-like, or nearly adult-like, for happy expressions on all measures. Children's sensitivity to other expressions continues to improve between 5 and 10 years of age (e.g., surprise, disgust, fear) or even after 10 years of age (e.g., anger, sad). The results indicate that there is a slow development of sensitivity to the expression of all basic emotions except happy. This slow development may impact children's social and cognitive development by limiting their sensitivity to subtle expressions of disapproval or disappointment. (Contains 5 figures and 3 tables.)