Influence of local orientation cues on estimating the tilt of two-dimensional patterns.

Ten subjects estimated the orientation of elongated random patterns composed of dots or short line segments. The estimated overall orientation of the patterns was influenced by the local orientation of the composing lines. Thus, when they formed an angle of 5.7 deg with the orientation of the least-squared-distances axis (LS-axis) of the pattern there was an effect of 'attraction', and when this angle was 22.9 deg, an effect of 'repulsion'. Estimated orientation coincided with the orientation of the LS-axis for angles of 11.5 and 45.8 deg, and when the patterns were composed of dots. The results point to interactions between different mechanisms involved in orientation perception.