Abstract:

It was revealed that visual angle existed in visual image, and mental image influenced image operation. Kosslyn mentioned size effect in his image calculation theory, but didn’t think about how external factors might act on the internal visual image processing. Most research on mental image didn’t regard visual angle as a factor. Whether actual visual angles of objects influence image operation was explored in the present research.

Method
Two experiments were used to investigate the effects of visual angle on visual image scanning with the task of scanning the Euclidean distance on mental image. In Experiment 1, 3(visual angle: 2.7°, 5.5°and 8.2°)×3(scanning distance: 0.0cm, 0.4cm and 0.8cm) within-subject factorial design was taken to examine whether visual angle influence image scanning. Experiment 2 investigated how visual angle influence image scanning process with a 8 (visual angle: 2.7°, 4.1°, 5.5°，6.9°, 8.2°, 9.6°, 12.3°and 17.1°)×2 ( scanning distance: 0.4cm and 0.8 cm ) within-subject factorial design.

Results
The findings indicated that: (1) visual angle of stimulus did influence the scanning time of visual image, even though the scanning Euclidean distances were the same; (2) When the visual angle was in the range from 4°to 10°, scanning time was significantly shorter than that of visual angle outside this range, the shortest scanning time was found on 6.5°.

Conclusions
The present research dispelled the interferences of the category distance, and verified the distance effect in visual image. The size effect of visual angle was different from size effect of mental scan and distance effect. The present findings have significant theoretical values. They add to Kosslyn’s image calculation theory. The findings have important practical implications as well. For it can be applied to the design of panel, illustration, game, interface, screen, and other instruments both in work and daily life

Key words: visual image, mental scanning, visual angle, Euclidean distance