What is the age of mental rotation?

Already the earliest pictorial depictions show rotated objects, demonstrating evolutionary origins of mental rotation. Unlike children do with their drawing sheets, cave artists could not rotate the wall on which they were painting. This study investigated whether the fixation of the drawing medium, which prevented practical rotation, has an impact on drawing a rotated object N = 230 children at age five, seven and nine copied an original cave drawing which was adapted to modern time. In a 'natural drawing' condition, paper and model were loose, in a 'fixed' condition, the model could not be moved, and in a third 'completely fixed' condition, neither paper nor model could be moved. 5-year-olds could best draw rotated objects in the 'natural drawing' condition, while 9-year-olds could best draw rotated objects in the highly constrained, 'completely fixed' condition. Children who rotated their sheet of paper in the natural and fixed condition were drawing more rotated objects, independently of age. Additional analysis showed that besides practical rotation also other predictors were significant, i.e. the number of objects in the correct place, their relative size and spatial relation. These results showed that mental rotation is a complex, high-level ability, embedded in a set of spatial skills, which requires considerable information processing capacity, experience and practice, and may have been already present in some early human cultures. Thus, mental rotation would be an ontogenetically late, but phylogenetically ancient skill.