This study has three objectives: a) to describe the main differences in the crying patterns produced by the three affective states most closely related to crying: fear, anger and pain; b) to study the adults' accuracy in the recognition of the affective states related to the infant's crying, and c) to analyze the emotional reaction that infant crying elicits in the observers. Results reveal that the main differences appear in the ocular activity and in the pattern of weeping. The infants maintain their eyes open during the crying produced by fear and anger, but in the case of crying provoked by painful stimuli, the eyes remain closed almost all the time. In regard to the pattern of weeping, the crying gradually increase in the case of anger, but the weeping reaches its maximum intensity practically from the beginning in the case of pain and fear. In spite of these differences, it is not easy to know the cause that produces crying in infants, especially in the case of fear or anger. Although observers can't recognize the cause of crying, the emotional reaction is greater when the baby cries in pain than when the baby cries because of fear or anger.