23. The system of claim 21 , wherein determining a concreteness feature score includes: defining a plurality of bins, each bin being associated with a concreteness rating condition; selecting one or more of the plurality of bins, each selected bin's concreteness rating condition being satisfied by the predetermined concreteness rating assigned to the content word; determining the concreteness feature score based on the one or more bins selected.
21. The system of claim 16 , wherein the processing system is configured to execute steps comprising: for each content word in the plurality of training texts, determining a concreteness feature score based on a predetermined concreteness rating assigned to the content word; wherein the generating of the prediction model is further based on the concreteness feature scores.