Speech perception strategies shift instantly

To perceive speech listeners must decide how to prioritize information from multiple acoustic dimensions. Over the course of language learning, individuals form stable perceptual strategies which reflect the strength of the statistical relationship between values along particular acoustic dimensions and linguistic categories. However, despite this underlying stability, listeners respond to evidence about shifts in the reliability of acoustic dimensions as cues to categorization, changing their strategies. Here we show that such changes are maximally efficient: listeners will adjust after hearing just a single stimulus in which the relationship between acoustic cues diverges from the expected pattern. Furthermore, these shifts in strategy vanish as quickly as they appear, lasting only a single trial before returning to baseline. Finally, we show that shifts in cue weighting are resistant to distraction, occurring equally when speech is presented in quiet versus in informational masking. Speech perception strategies, therefore, are characterized by short-term fluctuation and long-term stability.