Abstract: The regularity effect has been found for naming low-frequency pictophonetic characters but not high-frequency pictophonetic characters. However, all or most of the characters used in these studies had their phonetic radicals on the right. Therefore, the results may suggest a processing pattern that is only applicable to these characters. In the present study, three experiments were conducted to investigate the regularity effect for naming four types of pictophonetic characters: left-right structure with their phonetic radicals on the left; left-right structure with their phonetic radicals on the right; upper-lower structure with their phonetic radicals on top; and upper-lower structure with their phonetic radicals on the bottom. In this way, we were able to explore effects of the positions of phonetic radicals on the regularity effect.
In the first experiment, only characters with their phonetic radicals on the right were tested. The results a) duplicated the regularity effect for low-frequency characters that was shown in previous studies in which the positions of phonetic radicals were not manipulated and b) displayed a reversed regularity effect for naming the high-frequency characters. In the second experiment, characters with their phonetic radicals in the left and right positions were examined. The regularity effect was found for naming the low-frequency characters with their phonetic radicals on the right, and a reversed regularity effect was found for naming the high-frequency characters with their phonetic radicals on the left. In the third experiment, characters with their phonetic radicals in the upper and lower positions were tested. The regularity effect was found for naming the low-frequency characters with their phonetic radicals in the lower position and both the low- and high-frequency characters with their phonetic radicals in the upper position, but a reversed regularity effect was obtained for naming the high-frequency characters with their phonetic radicals in the lower position.
These results indicate that when phonetic radicals are located in the right or lower positions, where their pronunciations are easily activated, the regularity effect is applicable to naming low-frequency characters whereas there is a reversed regularity effect or no regularity effect for naming high-frequency characters. The reversed regularity effect is more sensitive to position changes of phonetic radicals for the left-right structure of characters but less sensitive to changes in the upper-lower structure of characters.
We propose that the positions of phonetic radicals may be a spatial attribute of the sub-lexical units that determines the convenience of the activation of their pronunciation. Word frequency may be a lexical attribute that restricts the convenience and may regulate the direction of the effects of the positions of phonetic radicals on the regularity effect.

Key words: pictophonetic characters, regularity effect, positions of phonetic radicals, word frequency, sub- lexical level processing