Since the work of Hubel and Wiesel, it is generally accepted that visual orientation and direction selectivity are achieved by processes in the visual cortex in the higher mammals.

Further more, we give an explanation of the intrinsic implication of the present method and our comprehension about directional orientational selectivity and preferred direction orientation.

Most of the researches of selectivity of fishing gear ignored the between-haul Variation which is caused by uncontrolled factors such as the depth of water, direction and velocity of wind and current.