The Acoustic Features and Didactic Function of Foreigner Directed Speech: A literature Review.

Abstract

This review considers the acoustic features of a clear speech register directed to non-native listeners known as Foreigner Directed Speech (FDS). We identify vowel hyperarticulation and low speech rate as the most representative acoustic features of FDS; other features, including wide pitch range and high intensity, are still under debate.We also discuss factors that may influence the outcomes and characteristics of FDS. We start by examining accommodation theories (Lindblom, 1990), outlining the reasons why FDS is likely to serve a didactic function by helping listeners acquire a second language (L2). We examine how this speech register adapts to listeners’ identities and linguistic needs, suggesting that FDS also takes listeners’ L2 proficiency into account. To confirm the didactic function of FDS, we compare it to other clear speech registers, specifically Infant Directed Speech and Lombard Speech. However, our review reveals that research has not yet established whether FDS, in fact, succeeds as a didactic tool that supports L2 acquisition. Our review reveals a complex set of contextual factors that determine specific realisations of FDS, which need further exploration. We conclude our review by summarising open questions and indicating directions and recommendations for future research.

Phonetic Accommodation in Non-native Directed Speech Supports L2 Word Learning and Pronunciation

“…An important consideration is that the present study used an online method to collect participants' responses. Several studies have addressed the question of whether online experiments provide reliable results and revealed that chronometric experiments for speech production can be implemented online without information loss (Anwyl-Irvine et al, 2020; Bridges et al, 2020;Fairs & Strijkers, 2021;Piazza, Kartushina, et al, 2022;Vogt et al, 2021). Thus, we are con dent in sustaining that the differences we found between speech register groups were genuine and not driven by the online setting.…”

The effect of clear speech to foreign-sounding interlocutors on native listeners’ perception of intelligibility

“…Although the appropriate spoken word identification and therefore speech intelligibility had previously been found to be affected by how accurate vowels are articulated (Liu et al, 2005;Weismer et al, 2001), other acoustic-phonetic features have also been highlighted in clear speech perception such as increased vowel length and word length (Bond and Moore, 1994;Scarborough et al, 2007). For example, increased word length was observed to be part of clear speech (Bond and Moore, 1994;Piazza et al, 2021) and increased vowel length was reported in speech to foreigners (Ashby, 2004;Sankowska et al, 2011). It could therefore be stated that it is a combination of vowel space together with other acoustic-phonetic features that might contribute to clear speech.…”

Phonetic accommodation in non-native directed speech supports L2 word learning and pronunciation

“…An important consideration is that the present study used an online method to collect participants' responses. Several studies have addressed the question of whether online experiments provide reliable results and revealed that chronometric experiments for speech production can be implemented online without information loss [74][75][76][77][78] . Thus, we are confident in sustaining that the differences we found between speech register groups were genuine and not driven by the online setting.…”