A Noisy-Channel Approach to Depth-Charge Illusions

Abstract

The “depth-charge” sentence, No head injury is too trivial to be ignored, is often interpreted as “no matter how trivial head injuries are, we should not ignore them” while the literal meaning is the opposite as “we should ignore them”. Four decades of research have failed to resolve the source of this entrenched semantic illusion. Here we adopt the noisy-channel framework for language comprehension to provide a potential explanation. We hypothesize that depth-charge sentences result from production errors whereby comprehenders derive the interpretation by weighing the plausibility of possible readings of the depth-charge sentences against the likelihood for plausible sentences to be produced with errors. In four experiments, we find that (1) the more plausible the intended meaning of the depth-charge sentence is, the more likely the sentence is to be misinterpreted; (2) the higher the likelihood of our hypothesized noise operations, the more likely depth-charge sentences are to be misinterpreted. These results suggest that misinterpretation is affected by both world knowledge and the distance between the depth-charge sentence and a plausible alternative, which is consistent with the noisy-channel framework.

Keywords: depth-charge sentence, semantic illusion, noisy-channel framework, speech error, language comprehension