That's a fascinating example of how architectural design can be influenced by the predominance of right-handedness in a population. The fact that castle staircases were built with a clockwise spiral, allowing defenders to swing their swords with their right hands while attackers were limited by the wall, highlights the importance of handedness in medieval combat.

This example supports the idea that the predominance of right-handedness in human populations has influenced the design of various structures and tools throughout history, often to the disadvantage of left-handed individuals. In this case, the design of castle staircases created a significant advantage for right-handed defenders, while left-handed attackers were put at a disadvantage.

This example also illustrates the point that conventions, such as the design of castle staircases, can be in conflict with an individual's strengths, as you mentioned. Left-handed individuals, who may have been equally skilled in combat, were nevertheless disadvantaged by the design of the staircases, which favored right-handed defenders.