A study conducted by a United States child psychiatrist, Kyle D. Pruett, found that infants between 7 and 30 months responded more favourably to being picked up by their fathers. Pruett also found that a father's parenting style is beneficial for a child's physical, cognitive, emotional and behavioural development. Mothers reassure toddlers when they become frustrated while fathers encourage them to manage their frustration. This helps the children learn to deal with stress and frustration. A long-term study Pruett conducted proved that a father's active involvement with his children, from birth to adolescence, promotes greater emotional balance, stronger curiosity and a stronger sense of self-assurance in the child.