Frequency trajectory is a better measure to investigate age-limited learning effects than age of acquisition (AoA) ratings (Zevin, J. D., & Seidenberg, M. S. (2002). "Age of acquisition effects in word reading and other tasks." "Journal of Memory and Language, 47"(1), 1-29). The current study uses frequency trajectory as a variable to investigate age-limited learning effects in Chinese character recognition, and tests predictions of the arbitrary mapping hypothesis as applied in a non-alphabetic writing system. In Experiment 1, regression analyses showed that, compared to rated AoA, frequency trajectory of characters was less affected by other lexical properties, and could explain a significant proportion of variance of AoA. In Experiment 2, the frequency trajectory and predictability from orthography to pronunciation of characters were orthogonally manipulated in a character naming task. The frequency trajectory effect appeared only for the arbitrary mapping condition. In Experiment 3, frequency trajectory and predictability from orthography to meaning of characters were manipulated in a semantic category judgment task. The frequency trajectory effects were found only when the mapping from orthography to semantic is less consistent. In summary, the study confirmed that AoA is a genuine factor affecting word processing, and the AoA effects were limited to those situations in which mapping between input and output representation was arbitrary. These results provide strong cross-linguistic evidence in support of the arbitrary mapping hypothesis. (Contains 6 tables.)