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Vowel hypo-and hyperarticulation (VHH) was investigated in Swedish infant-directed speech (IDS) to Swedish 12-month-olds using a measure that normalizes across speakers and vowels: the vhh-index. The vhh-index gives the degree of VHH for each individual vowel token, which allows for analysis of the dynamics of VHH within a conversation. Using both the vhh-index and traditional measures of VHH, the degree of VHH was compared between Swedish IDS and ADS. The vowel space area was larger in IDS than in ADS, and the average vhh-index as well as the modal value was higher in IDS than in ADS. Further, the proportion of vowel tokens that were highly hyperarticulated (vhh-index > 75th percentile) were fewer in ADS than in IDS. Vowels in Swedish IDS to 12-month-olds are thus concluded to be hyperarticulated compared to vowels in Swedish ADS, both in terms of degree and frequency. Findings are in line with previous reports on VHH in Swedish IDS as well as on VHH in IDS to infants around 12 months in other languages. The study considers the importance of robust formant estimation, highlights the need for replication of studies on VHH in IDS on previously studied languages and ages, and discusses the benefits of the vhh-index. Those benefits include that it normalizes across speakers and vowels, can be used for dynamic measures within speech samples, and permits analyses on token-level.

The amplitude of the event-related N1 wave decreases with repeated stimulation. This repetition-attenuation has not previously been investigated in response to variable auditory stimuli, nor has the relative impact of acoustic vs. perceptual category repetition been studied. In the present study, N1 repetition-attenuation was investigated for speech and spectrally rotated speech with varying degrees of acoustic and perceptual category variation. In the speech condition, participants (n = 19) listened to stimulus trains consisting of either the same vowel exemplar (no variability condition), different exemplars of the same vowel (low variability condition), or different exemplars of two different vowels (high variability condition). In the rotated speech condition, the spectrally rotated counterparts of the vowels were presented. Findings show N1 repetition-attenuation in the face of acoustic and perceptual category variability, but no impact of the degree of variability on the degree of N1 attenuation. Speech stimuli resulted in less attenuation than the acoustically matched non-speech stimuli, which is in line with previous findings. It remains unclear if the attenuation of the N1 wave is reduced as a result of stimuli being perceived as belonging to perceptual categories or as a result of some other characteristic of speech.

Parental responsive behaviour in communication has a positive effect on child speech and language development. Absence of canonical babbling (CB) in 10-month-old infants is considered a risk factor for developmental difficulties, yet little is known about parental responsiveness in this group of children. The purpose of the current study was to examine proportion and type of parental responsive utterances after CB and vocalization utterances respectively in a clinical group of children with otitis media with effusion, with or without cleft palate. Audio-video recordings of interactions in free play situations with 22 parents and their 10-monthold infants were used, where 15 infants had reached the CB stage and 7 infants had not. Fifty consecutive child utterances were annotated and categorized as vocalization utterance or CB utterance. The parent's following contingent response was annotated and labelled as acknowledgements, follow-in comments, imitations/expansions or directives. The Average intra-judge agreement was 90%, and the average interjudger agreement was 84%. There was no significant difference in proportion contingent responses after vocalizations and CB, neither when considering all child utterances nor the child's babbling stage. However, imitations/expansions tended to be more common after CB in the typical babbling group, whereas acknowledgements were more common after CB in the late babbling group. Our findings imply that responsiveness is a supportive strategy that is not fully used by parents of children with late babbling. Implications for further research as well as parent-directed intervention for children in clinical groups with late babbling are suggested.

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