Stockholm university

Iris-Corinna Schwarz

About me

I am a lecturer in special education, docent in Linguistics and a researcher at Stockholm Babylab.


I have been teaching in Higher Education since 2003.

I mainly teach courses in child language development and neurolinguistics, but also in research methodology, experimental design and project courses, both in English and Swedish.




I am interested in how infants develop language in interaction with their environment and how this process manifests in the brain. I study infant-directed speech of parents, parent-infant interaction and the neural basis of speech perception and turn-taking in adults and infants.

Research projects


A selection from Stockholm University publication database

  • Amount of speech exposure predicts vowel perception in four- to eight-month-olds

    2019. Ellen Marklund, Iris-Corinna Schwarz, Francisco Lacerda. Developmental Cognitive Neuroscience 36


    During the first year of life, infants shift their focus in speech perception from acoustic to linguistic information. This perceptual reorganization is related to exposure, and a direct relation has previously been demonstrated between amount of daily language exposure and mismatch response (MMR) amplitude to a native consonant contrast at around one year of age. The present study investigates the same relation between amount of speech exposure and MMR amplitude to a native vowel contrast at four to eight months of age. Importantly, the present study uses spectrally rotated speech in an effort to take general neural maturation into account. The amplitude of the part of the MMR that is tied specifically to speech processing correlates with amount of daily speech exposure, as estimated using the LENA system.

    Read more about Amount of speech exposure predicts vowel perception in four- to eight-month-olds
  • Using rotated speech to approximate the acoustic mismatch negativity response to speech

    2018. Ellen Marklund, Francisco Lacerda, Iris-Corinna Schwarz. Brain and Language 176, 26-35


    The mismatch negativity (MMN) response is influenced by the magnitude of the acoustic difference between standard and deviant, and the response is typically larger to linguistically relevant changes than to linguistically irrelevant changes. Linguistically relevant changes between standard and deviant typically co-occur with differences between the two acoustic signals. It is therefore not straightforward to determine the contribution of each of those two factors to the MMN response. This study investigated whether spectrally rotated speech can be used to determine the impact of the acoustic difference on the MMN response to a combined linguistic and acoustic change between standard and deviant. Changes between rotated vowels elicited an MMN of comparable amplitude to the one elicited by a within-category vowel change, whereas the between-category vowel change resulted in an MMN amplitude of greater magnitude. A change between rotated vowels resulted in an MMN ampltude more similar to that of a within-vowel change than a complex tone change did. This suggests that the MMN amplitude reflecting the acoustic difference between two speech sounds can be well approximated by the MMN amplitude elicited in response to their rotated counterparts, in turn making it possible to estimate the part of the response specific to the linguistic difference.

    Read more about Using rotated speech to approximate the acoustic mismatch negativity response to speech
  • The LENATM system applied to Swedish

    2017. Iris-Corinna Schwarz (et al.). Proceedings of Interspeech 2017, 2088-2092


    The Language Environment Analysis system LENATM is used to capture day-long recordings of children’s natural audio environment. The system performs automated segmentation of the recordings and provides estimates for various measures. One of those measures is Adult Word Count (AWC), an approximation of the number of words spoken by adults in close proximity to the child. The LENA system was developed for and trained on American English, but it has also been evaluated on its performance when applied to Spanish, Mandarin and French. The present study is the first evaluation of the LENA system applied to Swedish, and focuses on the AWC estimate. Twelve five-minute segments were selected at random from each of four day-long recordings of 30-month-old children. Each of these 48 segments was transcribed by two transcribers,and both number of words and number of vowels were calculated (inter-transcriber reliability for words: r = .95,vowels: r = .93). Both counts correlated with the LENA system’s AWC estimate for the same segments (words: r = .67, vowels: r = .66). The reliability of the AWC as estimated by the LENA system when applied to Swedish is therefore comparableto its reliability for Spanish, Mandarin and French.

    Read more about The LENATM system applied to Swedish
  • OZI: Australian English Communicative Development Inventory

    2016. Marina Kalashnikova, Iris-Corinna Schwarz, Denis Burnham. First language 36 (4), 407-427


    For more than 20 years, the MacArthur–Bates Communicative Development Inventory(CDI) and its adaptations for languages other than English have been used as reliable measures of infants’ and toddlers’ early receptive and productive vocabulary size. This article introduces the OZI, the Australian English adaptation of the MacArthur–Bates CDI, now normed for 12- to 30-month-old children. The findings of two studies are presented: (1) a comparison study that demonstrated that toddlers (N = 64) acquiring Australian English(24- and 30-month-olds) obtain higher productive vocabulary scores on the OZI than the MacArthur–Bates CDI; and (2) an OZI norming study that included 12- to 30-month-old Australian infants and toddlers (N = 1496). These studies provide (i) evidence for the greater applicability of the OZI for infants and toddlers learning Australian English and (ii) productive vocabulary acquisition norms for Australian English for ages 12–30 months, a research and diagnostic tool highly anticipated by researchers and clinicians around Australia.

    Read more about OZI: Australian English Communicative Development Inventory
  • Pause and utterance duration in child-directed speech in relation to child vocabulary size

    2015. Ulrika Marklund (et al.). Journal of Child Language 42 (5), 1158-1171


    This study compares parental pause and utterance duration in conversations with Swedish speaking children at age 1;6 who have either a large, typical, or small expressive vocabulary, as measured by the Swedish version of the McArthur-Bates CDI. The adjustments that parents do when they speak to children are similar across all three vocabulary groups; they use longer utterances than when speaking to adults, and respond faster to children than they do to other adults. However, overall pause duration varies with the vocabulary size of the children, and as a result durational aspects of the language environment to which the children are exposed differ between groups. Parents of children in the large vocabulary size group respond faster to child utterances than do parents of children in the typical vocabulary size group, who in turn respond faster to child utterances than do parents of children in the small vocabulary size group.

    Read more about Pause and utterance duration in child-directed speech in relation to child vocabulary size

Show all publications by Iris-Corinna Schwarz at Stockholm University