If young co-occurs with mature in a different pseudodocument (AGE might be a candidate), this results in a situation where (i) young and mature share one or more latent topics and (ii) the topic proportions for the attributes MATURITY and AGE will become similar to the extent of common words in their pseudodocuments.
the final attribute model is expected to assign a (small) positive probability to the relation between mature and MATURITY without observing it in the training data.