It has been suggested that animals subjected to loud noise at an early age will not be afraid of such noises later in life if the early experience occurred in the presence of the mother. Forty infant rats were used to test the suggestion, half being exposed to noise in the presence of their mothers and half when the mother was not present. When the rats were one year old their response to the same loud noise was videorecorded. Two independent judges examined their behaviour to determine whether the animal "froze" when the noise was played. There was perfect agreement between the judges. The total number of rats which were rated as being afraid of the noise in each group was recorded.