When speaking in any language, speakers must conceptualize what they want to say before they can formulate and articulate their message. We present two experiments employing a novel experimental paradigm in which the formulating and articulating stages of speech production were kept identical across conditions of differing conceptualizing difficulty. We tracked the effect of difficulty in conceptualizing during the generation of speech (Experiment 1) and during the abandonment and regeneration of speech (Experiment 2) on speaking fluency by Dutch native speakers in their first (L1) and second (L2) language (English). The results showed that abandoning and especially regenerating a speech plan taxes the speaker, leading to disfluencies. For most fluency measures, the increases in disfluency were similar across L1 and L2. However, a significant interaction revealed that abandoning and regenerating a speech plan increases the time needed to solve conceptual difficulties while speaking in the L2 to a greater degree than in the L1. This finding supports theories in which cognitive resources for conceptualizing are shared with those used for later stages of speech planning. Furthermore, a practical implication for language assessment is that increasing the conceptual difficulty of speaking tasks should be considered with caution.

This article presents the ventriloquist paradigm, an innovative method for studying speech processing in dialogue whereby participants interact face-to-face with a confederate who, unbeknownst to them, communicates by playing pre-recorded speech. Results show that the paradigm convinces more participants that the speech is live than a setup without the face-to-face element, and it elicits more interactive conversation than a setup in which participants believe their partner is a computer. By reconciling the ecological validity of a conversational context with full experimental control over phonetic exposure, the paradigm offers a wealth of new possibilities for studying speech processing in interaction.

Lexically guided perceptual learning has traditionally been studied with ambiguous consonant sounds to which native listeners are exposed in a purely receptive listening context. To extend previous research, we investigate whether lexically guided learning applies to a vowel shift encountered by nonnative listeners in an interactive dialogue. Dutch participants played a two-player game in English in either a control condition, which contained no evidence for a vowel shift, or a lexically constraining condition, in which onscreen lexical information required them to re-interpret their interlocutor's /ɪ/ pronunciations as representing /ɛ/. A phonetic categorization pre-test and post-test were used to assess whether the game shifted listeners' phonemic boundaries such that more of the /ɛ/-/ɪ/ continuum came to be perceived as /ɛ/. Both listener groups showed an overall post-test shift toward /ɪ/, suggesting that vowel perception may be sensitive to directional biases related to properties of the speaker's vowel space. Importantly, listeners in the lexically constraining condition made relatively more post-test /ɛ/ responses than the control group, thereby exhibiting an effect of lexically guided adaptation. The results thus demonstrate that non-native listeners can adjust their phonemic boundaries on the basis of lexical information to accommodate a vowel shift learned in interactive conversation.

Despite the importance of conscious awareness in second language acquisition theories, little is known about how L2 speech perception can be improved by explicit phonetic instruction. This study examined the relationship between phonological awareness and perception in Dutch younger and older adult L2 listeners, focusing on English contrasts of two types: a familiar contrast in an unfamiliar position (word-final /t/-/d/) and an unfamiliar contrast (/æ/-/ε/). Awareness was assessed with a task in which written minimal pairs and homophone pairs had to be judged as sounding the same or different. Perception was assessed with a two-alternative forced-choice identification task with auditorily presented words from minimal pairs. We investigated whether listeners’ awareness and perception improved after a video-based explicit instruction that oriented their attention to one of these contrasts, and we tested whether including information about the phonetic cue of vowel duration increased learning. Awareness and perception of each contrast were shown to be moderately correlated at the study’s outset. Furthermore, awareness and perception for each contrast generally improved more after the instruction drawing attention to that contrast. However, the effectiveness of explicit phonetic instruction varied depending on the combination of the contrast, cue information, and listener age group.