The unavoidable dependence of modalities in evaluation of reading (and listening) とはどういう意味ですか?

質問を翻訳

Strictly speaking, however, in the absence of actions that indicate comprehension, it is impossible to know whether the reader did not understand the reading or is unable (or reluctant) to do something that would indicate comprehension. It is also possible that there is simply a delay in the occurrence of desired observable actions.
The unavoidable dependence of modalities in evaluation of reading (and listening) can affect the validity of evaluation activities, especially in languages like Japanese and Chinese, whose orthography is more complex than the alphabetic writing system.