Final answer:
The speed at which people perform mental rotations depends on their spatial ability, as it involves the perception and understanding of three-dimensional space.
Step-by-step explanation:
The speed at which people perform mental rotations depends on the spatial ability. This is because spatial ability involves the understanding of objects in three-dimensional space, which is essential to mentally rotating an object. The further an object needs to be rotated, typically the more complex the mental task becomes and the longer it can take.
From the options provided (Reaction Time, Working Memory, Spatial Ability, Perceptual Speed), the correct answer is Spatial Ability.