Running title: Lexical frequency and acoustic reduction ABSTRACTThis study investigates the effects of lexical frequency on the durational reduction of morphologically complex words in spoken Dutch. The hypothesis that high-frequency words are more reduced than low-frequency words was tested by comparing the durations of affixes occurring in different carrier words. Four Dutch affixes were investigated, each occurring in a large number of words with different frequencies. The materials came from a large database of face-to-face conversations. For each word containing a target affix, one token was randomly selected for acoustic analysis. Measurements were made of the duration of the affix as a whole and the durations of the individual segments in the affix. For three of the four affixes, a higher frequency of the carrier word led to shorter realizations of the affix as a whole, individual segments in the affix, or both. Other relevant factors were the sex and age of the speaker, segmental context, and speech rate. To accommodate for these findings, models of speech production should allow word frequency to affect the acoustic realizations of lower-level units, such as individual speech sounds occurring in affixes.

Purpose Service robots can offer benefits to consumers (e.g. convenience, flexibility, availability, efficiency) and service providers (e.g. cost savings), but a lack of trust hinders consumer adoption. To enhance trust, firms add human-like features to robots; yet, anthropomorphism theory is ambiguous about their appropriate implementation. This study therefore aims to investigate what is more effective for fostering trust: appearance features that are more human-like or social functioning features that are more human-like. Design/methodology/approach In an experimental field study, a humanoid service robot displayed gaze cues in the form of changing eye colour in one condition and static eye colour in the other. Thus, the robot was more human-like in its social functioning in one condition (displaying gaze cues, but not in the way that humans do) and more human-like in its appearance in the other (static eye colour, but no gaze cues). Self-reported data from 114 participants revealing their perceptions of trust, anthropomorphism, interaction comfort, enjoyment and intention to use were analysed using partial least squares path modelling. Findings Interaction comfort moderates the effect of gaze cues on anthropomorphism, insofar as gaze cues increase anthropomorphism when comfort is low and decrease it when comfort is high. Anthropomorphism drives trust, intention to use and enjoyment. Research limitations/implications To extend human–robot interaction literature, the findings provide novel theoretical understanding of anthropomorphism directed towards humanoid robots. Practical implications By investigating which features influence trust, this study gives managers insights into reasons for selecting or optimizing humanoid robots for service interactions. Originality/value This study examines the difference between appearance and social functioning features as drivers of anthropomorphism and trust, which can benefit research on self-service technology adoption.

This study explores the effects of informational redundancy, as carried by a word's morphological paradigmatic structure, on acoustic duration in read aloud speech. The hypothesis that the more predictable a linguistic unit is, the less salient its realization, was tested on the basis of the acoustic duration of interfixes in Dutch compounds in two datasets: One for the interfix -s-͑1155 tokens͒ and one for the interfix -e͑n͒-͑742 tokens͒. Both datasets show that the more probable the interfix is, given the compound and its constituents, the longer it is realized. These findings run counter to the predictions of information-theoretical approaches and can be resolved by the Paradigmatic Signal Enhancement Hypothesis. This hypothesis argues that whenever selection of an element from alternatives is probabilistic, the element's duration is predicted by the amount of paradigmatic support for the element: The most likely alternative in the paradigm of selection is realized longer.

This study investigates the relationship between word repetition, predictabil-ityfrom neighbouring words, and articulatory reduction in Dutch. For the sevenmost frequent words ending in the adjectival suffix -lijk, 40 occurrences were ran-domlyselected from a large database of face-to-face conversations. Analysis ofthe selected tokens showed that the degree of articulatory reduction (as measuredby duration and number of realized segments) was affected by repetition, pre-dictabilityfrom the previous word and predictability from the following word.Interestingly, not all of these effects were significant across morphemes and tar-getwords. Repetition effects were limited to suffixes, while effects of predictabil-ityfrom the previous word were restricted to the stems of two of the seven targetwords. Predictability from the following word affected the stems of all targetwords equally, but not all suffixes. The implications of these findings for models ofspeech production are discussed.

PurposeConversational agents (chatbots, avatars and robots) are increasingly substituting human employees in service encounters. Their presence offers many potential benefits, but customers are reluctant to engage with them. A possible explanation is that conversational agents do not make optimal use of communicative behaviors that enhance relational outcomes. The purpose of this paper is to identify which human-like communicative behaviors used by conversational agents have positive effects on relational outcomes and which additional behaviors could be investigated in future research.Design/methodology/approachThis paper presents a systematic review of 61 articles that investigated the effects of communicative behaviors used by conversational agents on relational outcomes. A taxonomy is created of all behaviors investigated in these studies, and a research agenda is constructed on the basis of an analysis of their effects and a comparison with the literature on human-to-human service encounters.FindingsThe communicative behaviors can be classified along two dimensions: modality (verbal, nonverbal, appearance) and footing (similarity, responsiveness). Regarding the research agenda, it is noteworthy that some categories of behaviors show mixed results and some behaviors that are effective in human-to-human interactions have not yet been investigated in conversational agents.Practical implicationsBy identifying potentially effective communicative behaviors in conversational agents, this study assists managers in optimizing encounters between conversational agents and customers.Originality/valueThis is the first study that develops a taxonomy of communicative behaviors in conversational agents and uses it to identify avenues for future research.