Whether dots moving in two directions appear coherent or transparent depends on directional biases induced by...

When two random-dot patterns moving in different directions are superimposed, motion appears coherent or transparent depending on the directional difference. In addition, when a pattern is surrounded by another pattern that is moving, the perceived motion of the central stimulus is biased away from the direction of the surrounding motion. That phenomenon is known as induced motion. How is the perception of motion coherence and transparency modulated by surrounding motion? It was found that two random-dot horizontal motions surrounded by another stimulus in downward motion appeared to move in two oblique directions: left-up and right-up. Consequently, when motion transparency occurs, each of the two motions interacts independently with the induced motion direction. Furthermore, for a central stimulus consisting of two physical motions in left-up and right-up directions, the presence of the surrounding stimulus in a vertical motion modulated the perceptual solution of motion coherence/transparency such that if interactions with an induced motion signal narrow the apparent directional difference between the two central motions, then motion coherence is preferred over motion transparency. Therefore, whether a moving stimulus is perceived as coherent or transparent is determined based on the internal representation of motion directions, which can be altered by spatial interactions between adjacent regions.