A study on audiovisual processing in noise in typically reading adults

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The main question we tried to answer in the current research was: Do adults without dyslexia identify steps from an audio-visually presented continuum similar in a modulated noise condition and a stationary noise condition? In order to contribute to this investigation, we determined: I) if typical readers show different audiovisual perception of phonetic categories in two different noise conditions, II) if typical readers show different reaction times in the two different noise conditions and III) if in typically readers a correlation is present between speechreading ability and the visual influence on audio-visual perception of phonetic categories. 11 typically reading adults were asked to participate in the study. We used a phonetic categorization task with a /p/-/t/-continuum. Five auditory steps along the continuum were combined with five visual steps along the continuum, both presented unimodally and bimodally combined with different types of noise (speech-shaped steady state noise and speech-shaped modulated noise). We did not find a statistically difference in audiovisual perception of the phonetic categories between the two noise conditions, although the figure suggests there is a difference. It might, therefore, not be statistically significant due to the small sample size, further research is suggested. We also did not find a statistically significant difference in the reaction times between responses in the different noise conditions. Since, again, it can be seen from the figure that the reaction times are (mostly) slower for the modulated, we argue that this might also be due to the small sample size. Another explanation could be that the modulation used in the current study did not result in a difference in reaction time between the modulated noise condition and the stationary noise condition. Also, not correlation was found between the speech-reading abilities and the visual influence on the audio-visual perception of phonetic categories.
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