Stimulation Of The Impact Of The Perspective Of The Size On Mental Rotation Rate And The Erp Amplitude

Mental rotation is an important ability for the transformation of mental images.Since the publication of an important research article by Shepard and Metzler in 1971,the study on mental imagery and mental rotation increased rapidly.Studies have found that the reaction time increase linearly as more mental rotation has to be executed.The ERPs studies of mental rotation have found that the positivity at parietal electrode sites become more negative as more mental rotation has to be executed.This effect was thought to be connected with the processing of mental rotation.Shwartz(cited in Kosslyn,1980) and Suzuki and Nakata(1988) used two-dimentional and three-dimentional figures exemined whether the visual angle of the stimuli had effects on the speed of mental rotation respectively.However,their results were inconsistent:Shwartz(cited in Kosslyn, 1980) found that the rotation rate of the stimuli with biger visual angle was more slower;but Suzuki and Nakata(1988) found that the rotation rate of the stimuli with smaller visual angle was more slower in the lit condition.Qiu xiang(2006) studied this problem also.This study used two-dimentional figures and characters as experiment materials,and used ERPs technology to investigate whether the visual angle of the stimuli had effects on the rotation-related potentials.This study consisted of three experiments.Experiment 1 and 2 were behavioral experiments, used two-dimentional figures and characters as materials to investigate whether the visual angle of the stimuli had effects on the rotation rate,respectively.Experiment 3 was an ERP experiment which used characters as stimuli.The shapes of the two-dimentional figures used in experiment 1 were similar to "T",but the left and right side were different.The figures had two different sizes,and the length of the big ones was the double of the small ones.Because the distances between the eyes of the subjects and the stimuli were the same,the visual angle of the big in this direction was the double of the small ones.The present method of the stimuli was present two figures consequently,and the angle differences between the second one and the first one could be 0°,120°or 240°.The subjects had to rotate the second figure counterclockwise to the 0°orientation and then judge if the two figures have the same shape(if they were the same then they can superposition,if one of them was the mirror version of the other then they can't).The results indicated that,the visual angle of the stimuli had no effect on the rotation rate.Experiment 2 used characters with normal or mirror version as materials to validate the results of experiment 1.Also there were two sizes of the characters,and the length and the breath of the big were duble of the small,so as the visual angle. The method of the presentation of the stimuli was present one character per trial,and the version of it could be normal or mirror with its orientation was 0°or 120°or 240~°from uptight.The subjects had to rotate the character counterclockwise to the 0°orientation and then judge its version.The results were the same with experiment 1 which used two-dimentional figures as stimuli that the visual angle of the stimuli had no effect on the rotation rate.Experiment 3 was an ERP study that used 32 electrodes to record the EEG when the subjects do the experiment tasks.The method and procedure were similar to experiment 2,except that it increased the number of the characters and the repeated times of each condition.The behavioral data of this experiment indicated that,the visual angle of the stimuli had no effect on the rotation rate,so it was consistent with Experiment 1 and 2. This experiment found that the positivity at parietal electrode sites become more negative as the angle increased,in consistent with the ERPs studies of mental rotation before.So the effects of the rotation of big and small characters on the change of the positivity at parietal electrode sites were different.Generally speaking,the behavioral results of this study were different with studies before,as the data indicated that the visual angle of the stimuli had no effect on the rotation rate,which was consistent with Cooper's(1975) opinion.This study also found that the mental rotation of stimuli that with different sizes of visual angle had different effects on rotation-related potentials,which provided new evidence to the opinion that the positivity at parietal electrode sites become more negative as more rotation has to be executed reflected the processing of mental rotation.