Abstract: Age of acquisition (AoA) has recently drawn considerable attention as a determinant of lexical processing. Several hypotheses have been proposed to explain the mechanism of AoA effects. One of these hypotheses is the Phonological Completeness Hypothesis, which assumes that AoA effects arise at the level of phonological representation. Although it could explain some AoA effects in word naming, it failed to do so in a phonological segment experiment. It could also not explain the AoA effects in some experiments where phonological output was not necessary. Neither could it explain why there were AoA effects in picture naming tasks where semantic factors were invited but there were no AoA effects in Chinese Characters naming tasks where the phonetic factor was involved. Another important hypothesis is the Semantic Hypothesis, which assumes that at least parts of the AoA effect originates from the semantic system. According to this hypothesis, the order of acquisition has a lasting effect on the time needed to activate the meanings of words. It was supported in some semantic tasks but not in some other studies. Evidence against this hypothesis seemed also available from AoA studies on bilinguals. In the present study, three experiments were conducted to examine the locus of the age of acquisition effects in the processing of Chinese words of Putonghua-Chaoshan bilinguals, with the focus on testing the Semantic Hypothesis of AoA effects.
In Experiment 1, the bilinguals were required to name words and pictures. The stimuli were 36 single characters and 36 line drawings obtained from the Snodgrass and Vanderwart (1980). The 36 characters were 18 early- and 18 late-acquired characters. Each character was the Chinese name of one of the 36 line drawings. The aim was to compare the AoA effects between participants’ performance in picture and character naming tasks both in Chaoshan dialect and in Putonghua. To reduce the influence of the phonological output on the AoA effects in the picture naming task of Experiment 1 semantic category judgment task was used in Experiment 2, in which the bilinguals had to judge whether one of 32 early- and 32 late-acquired characters belongs to a certain the semantic category of “action” in both languages. In Experiment 3, the task of initial syllable monitoring was used in which an initial syllable and a Chinese character appeared in the screen at the same time and participants had to judge whether the stimuli matched in a specific language. The materials were 32 (16 early- and 16 late-acquired) characters in each category.
Error rates and reaction times for correct responses were analyzed with ANOVA by subject and by item. In Experiment1, there was an interaction between AoA and task in both languages: especially in Chaoshan dialect there was a substantial AoA effect in picture naming task (131ms), but there was no AoA effect in character naming task in both languages. In Experiment 2, the semantic category judgment task showed significant AoA effects in both languages (26ms and 21ms). In Experiment 3, there were no AoA effects in either Chaoshan dialect or in Putonghua. The results of the present study suggested that AoA effects could be partially produced within the semantic processing system, rather than only within the speech output system.

Key words: word AoA effects, bilinguals, semantic hypothesis, phonological completeness hypothesis