Speaker-specific processing and local context information: The case of speaking rate

To deal with variation in the speech signal, listeners rely on local context, such as speaking rate in a carrier sentence directly preceding a target, as well as more global properties of the speech signal, such as speaker-specific pronunciation variants. The present study addressed whether, despite its variability even within one speaker, habitual speaking rate can be tracked as a speaker-specific property and how such speaker-specific tracking of habitual rate would interact with effects of local-rate normalization. In two experiments, listeners were exposed to a 2-min dialogue between a fast and a slow speaker. At test, listeners categorized minimal word pair continua differing in the German /a/-/a:/ duration contrast spoken by the same two speakers. The results showed that listeners responded with /a:/ more often for the fast speaker but only when words were presented in isolation and not when presented with additional local-rate information. That is, despite the general assumption that duration cues and speaking rate are too variable to be used in a speaker-specific fashion, tracking habitual speaking rate may help speech perception. The results are discussed in relation to a belief-updating model of perceptual adaptation and exemplar models

Allophones, not phonemes in spoken-word recognition

We thank Nadia Klijn for helping to prepare and test participants in Experiment 1 and Rosa Franzke for help with Experiments 2 and 3. The second author is funded by an Emmy-Noether grant (nr. RE 3047/1-1) from the German Research Council (DFG). This work was also supported by a University of Malta Research Grant to the first author.What are the phonological representations that listeners use to map information about the segmental content of speech onto the mental lexicon during spoken-word recognition? Recent evidence from perceptual-learning paradigms seems to support (context-dependent) allophones as the basic representational units in spoken-word recognition. But recent evidence from a selective-adaptation paradigm seems to suggest that context-independent phonemes also play a role. We present three experiments using selective adaptation that constitute strong tests of these representational hypotheses. In Experiment 1, we tested generalization of selective adaptation using different allophones of Dutch /r/ and /l/ – a case where generalization has not been found with perceptual learning. In Experiments 2 and 3, we tested generalization of selective adaptation using German back fricatives in which allophonic and phonemic identity were varied orthogonally. In all three experiments, selective adaptation was observed only if adaptors and test stimuli shared allophones. Phonemic identity, in contrast, was neither necessary nor sufficient for generalization of selective adaptation to occur. These findings and other recent data using the perceptual-learning paradigm suggest that pre-lexical processing during spoken-word recognition is based on allophones, and not on context-independent phonemes.peer-reviewe

My English sounds better than yours: Second-language learners perceive their own accent as better than that of their peers

Second language (L2) learners are often aware of the typical pronunciation errors that speakers of their native language make, yet often persist in making these errors themselves. We hypothesised that L2 learners may perceive their own accent as closer to the target language than the accent of other learners, due to frequent exposure to their own productions. This was tested by recording 24 female native speakers of German producing 60 sentences. The same participants later rated these recordings for accentedness. Importantly, the recordings had been altered to sound male so that participants were unaware of their own productions in the to-be-rated samples. We found evidence supporting our hypothesis: participants rated their own altered voice, which they did not recognize as their own, as being closer to a native speaker than that of other learners. This finding suggests that objective feedback may be crucial in fostering L2 acquisition and reduce fossilization of erroneous patterns

Temporal contrast effects in human speech perception are immune to selective attention

Two fundamental properties of perception are selective attention and perceptual contrast, but how these two processes interact remains unknown. Does an attended stimulus history exert a larger contrastive influence on the perception of a following target than unattended stimuli? Dutch listeners categorized target sounds with a reduced prefix "ge-" marking tense (e.g., ambiguous between gegaan-gaan "gone-go"). In 'single talker' Experiments 1-2, participants perceived the reduced syllable (reporting gegaan) when the target was heard after a fast sentence, but not after a slow sentence (reporting gaan). In 'selective attention' Experiments 3-5, participants listened to two simultaneous sentences from two different talkers, followed by the same target sounds, with instructions to attend only one of the two talkers. Critically, the speech rates of attended and unattended talkers were found to equally influence target perception - even when participants could watch the attended talker speak. In fact, participants' target perception in 'selective attention' Experiments 3-5 did not differ from participants who were explicitly instructed to divide their attention equally across the two talkers (Experiment 6). This suggests that contrast effects of speech rate are immune to selective attention, largely operating prior to attentional stream segregation in the auditory processing hierarchy

Foreign Languages Sound Fast: Evidence from Implicit Rate Normalization

Anecdotal evidence suggests that unfamiliar languages sound faster than one's native language. Empirical evidence for this impression has, so far, come from explicit rate judgments. The aim of the present study was to test whether such perceived rate differences between native and foreign languages (FLs) have effects on implicit speech processing. Our measure of implicit rate perception was "normalization for speech rate": an ambiguous vowel between short /a/and long /a:/is interpreted as /a:/following a fast but as /a/following a slow carrier sentence. That is, listeners did not judge speech rate itself;instead, they categorized ambiguous vowels whose perception was implicitly affected by the rate of the context. We asked whether a bias towards long /a:/might be observed when the context is not actually faster but simply spoken in a FL. A fully symmetrical experimental design was used: Dutch and German participants listened to rate matched (fast and slow) sentences in both languages spoken by the same bilingual speaker. Sentences were followed by non-words that contained vowels from an /a-a:/duration continuum. Results from Experiments 1 and 2 showed a consistent effect of rate normalization for both listener groups. Moreover, for German listeners, across the two experiments, foreign sentences triggered more /a:/responses than (rate matched) native sentences, suggesting that foreign sentences were indeed perceived as faster. Moreover, this FL effect was modulated by participants' ability to understand the FL: those participants that scored higher on a FL translation task showed less of a FL effect. However, opposite effects were found for the Dutch listeners. For them, their native rather than the FL induced more /a:/responses. Nevertheless, this reversed effect could be reduced when additional spectral properties of the context were controlled for. Experiment 3, using explicit rate judgments, replicated the effect for German but not Dutch listeners. We therefore conclude that the subjective impression that FLs sound fast may have an effect on implicit speech processing, with implications for how language learners perceive spoken segments in a FL