Are there really interactive processes in speech perception?

On both empirical and theoretical grounds, we argue that the affirmative answer of McClelland et al. [1] is premature. Contrary to the predictions of the TRACE model, which postulates interactive processing in speech perception, there is no lexically mediated compensation for coarticulation when there is a lexical bias in interpretation of the preceding fricative [2]. This cannot be dismissed with criticism of the fricative-final lexical contexts and their distance from the stops (Box 3 in Ref. [1]). The contexts in Ref. [2] were effective – there was a lexical bias on the fricatives; and the timing was appropriate – there was a compensation effect with the same fricative-stop gap in the nonword-context conditions. Furthermore, we suggest that the evidence on compensation that purports to show interaction is unconvincing. Some apparent lexical effects [3,4] are possibly higher-order transitional-probability effects [2]. Others perhaps reflect learning about experimentinternal biases; indeed, the effect in Ref. [5] did not seem to increase over time, but this null result is not definitive because learning could have occurred in the practice block. Perceptual retuning can explain the selective-adaptation data (e.g. Ref. [6]). Retuning of phonetic perception can arise after only ten critical trials [7]; selective adaptation effects depend onmany more exposures (e.g. 768 in Ref. [6]). Thus, selective adaptation can follow from perceptual retuning. After listeners learn that the ambiguous phoneme is /s/, for example, it acts as an adaptor, reducing the number of /s/ responses to the test stimuli. Further analysis of the data in Ref. [6] reveals exactly this: early blocks of trials show retuning, whereas later blocks show adaptation (Figure 3 in Ref. [8]). The evidence onwhether there is on-line lexical influence on prelexical processes is thus inconclusive. However, consensus has been reached on the existence of lexical feedback for learning [7,9] and, as just shown, this can also explain apparent evidence of on-line interaction. Why might there be feedback that affects learning but not processing? Feedback for learning is helpful because it enables the listener to adjust to speaker-related variability [9], but feedback in on-line processing is not beneficial and could even be harmful [10]. These views are based on rational analysis [11]. Analyzing the nature of the perceptual task generated a hypothesis (thatwas confirmed inRef. [9]) about how speech perception should operate. According to the rational-analysis perspective, and McClelland et al. [1], the goal of the speech-recognition device is optimal interpretation. Bayesian methods