The detection of a potential danger is an important factor in avoiding harm. This is even more important for vulnerable populations, such as children. We explored whether children could recognise the potential for a dangerous encounter from observing the walk of an approaching person. Participants were divided into three age groups; over 18 year olds, 16-17 year olds and 13-15 year olds. Participants made judgments of nine, point light presentations of people walking on a treadmill. Ratings of intimidation made by participants were used to assess their ability to detect the walkers’ trait aggression. The ability to accurately detect trait aggression increased with age as did the consistency in ratings between individuals within the same age group. We highlight the importance of experiential learning in the acquisition of aggression detection skills.