An established finding in research on infant-directed speech (IDS) is that vowels are hyperarticulated compared to adult-directed speech (ADS). Studies showing this investigate point vowels, leaving us with a rather weak foundation for concluding whether IDS vowels are hyperarticulated within a particular language. The aim of this study was to investigate a large sample of vowels in IDS and to elicit speech in a natural situation for mother and infant. Acoustical and statistical analyses for /æ:, æ, ø:, ɵ, o:, ɔ, y:, y, ʉ:, ʉ, e:, ɛ/ show a selective increase in formant frequencies for some vowel qualities. In addition, vowels had higher fundamental frequency and were generally longer in IDS, but the difference between long and short vowels were comparable between IDS and ADS. With an additional front articulation and less lip protrusion in IDS compared to ADS, it is argued that IDS is hypoarticulated.
