Perception and control of altitude: splay and depression angles

In 3 experiments altitude control was examined as a function of texture type and forward speed. Four texture types were used: grid (rectangular grid with neutral colored cells); dot (small triangles distributed randomly on the ground surface); splay (rows of colored texture parallel to the direction of motion); and depression (rows of colored texture extending perpendicular to the direction of motion). The first 2 experiments required participants to track a constant altitude. Experiment 3 required participants to descend as low as possible without crashing. Results showed an interaction between texture type and forward speed. At low speeds, there was little difference between performance with the depression and splay textures. However, performance with the depression texture deteriorated with increasing forward speeds. Performance with the splay texture was independent of forward speed.