Relation between vowel hypo-/hyperarticulation and vocal affect in Swedish infant directed speech

Sammanfattning: Vowel hyperarticulation and hyper affect are two characteristics of infant-directed speech (IDS), reported in several studies. Vowel hyperarticulation has been suggested to be a way in which adults subconsciously facilitate infants’ language acquisition, but it has also been argued to be the acoustic by-product of an affective speaking style. The present thesis describes the expression of vocal affect in Swedish IDS at 12 months and investigates the relationship between vocal affect and vowel hypo-/hyperarticulation (VHH) on a speaker level. Naïve listeners (n = 23) rated affect valence in filtered samples of parents’ IDS and adult-directed speech (ADS). VHH was quantified by vowelspace area (VSA) for the same parents. In line with previous studies, IDS contained significantly more positive affect than ADS, illustrating that heightened positive affect is a distinct feature of Swedish IDS. Furthermore, no relationship was found between vocal affect and degree of VHH. However, a significant negative relationship was found between parents’ difference in VSA for IDS and ADS, and the difference in vocal affect for IDS and ADS. The results show that hyper affect was not associated with hyperarticulation of vowels. In general, parents that made affective adjustments in their IDS made smaller adjustments regarding VHH. The results support previous research suggesting that vowel hyperarticulation in IDS is not simply the result of an affective speaking style.