This article examines the acquisition of wh-questions in a Polish-Mandarin bilingual child (2;0-3;1) with a focus
on how computational difficulty shapes cross-linguistic influence. The analysis draws on a longitudinal corpus
of naturalistic interactions and targets the contrast between ‘what’ (Polish co, Mandarin shénme) and ‘where’ (Polish gdzie, Mandarin nǎlǐ) questions in Polish, Mandarin, and Polish-matrix (code-mixed) utterances. Two
complexity measures are applied: (1) a movement-based derivational index and (2) a feature-reassembly
index that incorporates the feature inventory, constructional markedness, and meaning-form mapping burden.
The results reveal a systematic wh-type asymmetry that is not captured by dominance alone. In Polish-directed
production, ‘what’ questions show stronger Mandarin influence, including frequent use of Mandarin wh-lexemes
and in-situ configurations, whereas ‘where’ questions more often display Polish-like fronting even
when Mandarin lexical material is used. In Mandarin-directed production, residual Polish influence is more
evident in the ‘where’ domain than in the ‘what’ domain. These patterns align with the feature-reassembly
metric: the Polish ‘what’ domain imposes a higher mapping burden due to case-conditioned alternants, while
the ‘where’ domain remains morphologically stable. The findings support a complexity-sensitive account
of selective cross-linguistic influence in bilingual wh-development.