Abstract: Age of Acquisition (AoA) refers to the age at which a word is first learnt, which is an important variable that has recently drawn considerable attention as a determinant of lexical processing. A large number of studies have found that words acquired earlier in life are processed more efficiently than words acquired late in life. Several hypotheses have been proposed to explain the origin of the AoA effects. One of these hypotheses is the Semantic Hypothesis, which assumes that at least parts of the AoA effect originate 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 (Van Loon-Vervoorn, 1985, 1989). Another hypothesis is the Phonological Completeness Hypothesis, which assumes that AoA effects arise at the level of phonological representation. The phonology of early-acquired words is stored wholly and completely, but as a child’s vocabulary increases, the phonology is assumed to be represented in a more fragmented form. Although it could explain some AoA effects in word naming (Brown & Watson, 1987), it failed to do so in a phonological segment experiment (Monaghan & Ellis, 2002). In present study, three experiments were conducted to examine the locus of the age of acquisition effects in the processing of Chinese words and Sign words of deaf college students, with the focus on testing the Semantic Hypothesis of AoA effects. In Experiment 1, the deaf students were required to use sign language to name characters and pictures. The stimuli were 44 single characters and 44 pictures obtained from the Snodgrass and Vanderwart (1980). The 44 characters were 22 early-acquired and 22 late-acquired characters respectively. The aim was to compare the AoA effects between deaf students’ performance in picture and character naming tasks. To reduce the influence of the phonological output on the deaf in the picture naming task of Experiment 1, semantic classification task was used in Experiment 2 and Experiment 3, in which deaf students had to judge whether one of 11 early-acquired and 11 late-acquired characters or pictures belongs to living things or non-living things. Reaction times for correct responses and error rates were analyzed by subject. In Experiment 1, there was an interaction between AoA and task, with substantial AoA effect in picture naming task, but no AoA effects in character naming task. In Experiment 2, the semantic classification task of character showed significant AoA effects. In Experiment 3, the significant AoA effects were also found in the task of picture classification of non-living things. However, error rates showed opposite trends in Experiment 2 and Experiment 3. It shows that deaf students had weaker awareness of semantic category. The results of the three experiments suggested that the AoA effects could be partially produced within semantic processing system effect because it can eliminates phonological factors in deaf to some extent.

Key words: Age of Acquisition, Chinese Sign Language, semantic hypothesis