Shepard and metzler found that the reaction time for solving mental rotation tasks as the difference in orientation from zero to 180 degrees.

increased, increased

Explanation:

Shepherd and Metzler(1971) tested mental rotation tasks on three dimensional objects. They concluded that the reaction time to determine if a pair of items matched or not was linealy proportional to the angle of rotation from the original position. That is the reaction time increases as the difference in orientation increase from zero to 180 degrees.

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