  Recently, Ferrer i Cancho and Moscoso del Prado Martin [arXiv:1209.1751]
argued that an observed linear relationship between word length and average
surprisal (Piantadosi, Tily, & Gibson, 2011) is not evidence for communicative
efficiency in human language. We discuss several shortcomings of their approach
and critique: their model critically rests on inaccurate assumptions, is
incapable of explaining key surprisal patterns in language, and is incompatible
with recent behavioral results. More generally, we argue that statistical
models must not critically rely on assumptions that are incompatible with the
real system under study.
