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Effects of task difficulty on infants normalization of naturalistic speech
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EFFECTS OF TASK DIFFICULTY ON INFANTS NORMALIZATION OF NATURALISTIC SPEECH C. Nathan Marti Department of Psychology, The University of Texas, Austin, TX 78712 The present studies investigate 11-month-olds’ ability to normalize naturalistic speech which varies on several dimensions. Dimensions of variability include fundamental frequency, amplitude, duration and speaker’s gender. Effects of task difficulty were assessed by comparing infants’ ability to recognize novel syllables during test trials based on the degree to which the familiarization speaker was characteristic of infant directed speech. Stimuli typical of infant directed speech should assist infants in forming a more accurate and detailed representation of the sequence. A modified headtum preference was used. After hearing a seven-syllable familiarization sentence, infants heard four test trials which differed from the familiarization sentence in the following ways: (1) no change, (2) the same sentence in a different voice, (3) the familiarization sentence with a syllable changed and (4) the familiarization sentence with both speaker’s voice and the final syllable changed. Experiments la and lb both contained four familiarization trials that differed only in the location of the syllabic change: ln Experiment la, the change was located in the final syllable and in Experiment lb, the change was located in the first stressed syllable (the second syllable overall). A MANOVA was conducted with looking times as the dependent measure revealing a main effect for speaker’s voice, F (1,61) = 4.41, p < .05, and a main effect for syllabic change, F (1,61) = 8.94, p c .Ol. There was also an interaction effect for speaker X syllabic change, F (1, 6 1) = 4.47, p c .05, and familiarization voice X speaker X syllabic change, F (1, 61) = 5.22, pc .05. In short, these findings indicated that infants distinguished between the syllabic change and no-change trials in the novel voices; however, infants failed to respond differentially to the change versus no change in the familiar voice. Furthermore, infants showed a greater interest in novel syllabic changes when familiarized with a female voice and speech typical of infant directed speech. The results provide evidence that 1l-month-old infants are indeed capable of normalizing naturalistic speech which varies in multiple dimensions. However, it appears that this is a difficult task which requires large amounts of familiarization and is assisted by stimuli characteristic of infant-directed speech. These results also indicate that task difficulty affects infants’ ability to detect changes in linguistic stimuli. In sum, it appears that normalization of naturalistic speech is assisted by an initial representation of a sequence possessing the exaggerated and attention holding properties typical of infant directed speech.
EFFECTS OF TASK DIFFICULTY ON INFANTS NORMALIZATION OF NATURALISTIC SPEECH C. Nathan Marti Department of Psychology, The University of Texas, Austin, TX 78712 The present studies investigate 11-month-olds’ ability to normalize naturalistic speech which varies on several dimensions. Dimensions of variability include fundamental frequency, amplitude, duration and speaker’s gender. Effects of task difficulty were assessed by comparing infants’ ability to recognize novel syllables during test trials based on the degree to which the familiarization speaker was characteristic of infant directed speech. Stimuli typical of infant directed speech should assist infants in forming a more accurate and detailed representation of the sequence. A modified headtum preference was used. After hearing a seven-syllable familiarization sentence, infants heard four test trials which differed from the familiarization sentence in the following ways: (1) no change, (2) the same sentence in a different voice, (3) the familiarization sentence with a syllable changed and (4) the familiarization sentence with both speaker’s voice and the final syllable changed. Experiments la and lb both contained four familiarization trials that differed only in the location of the syllabic change: ln Experiment la, the change was located in the final syllable and in Experiment lb, the change was located in the first stressed syllable (the second syllable overall). A MANOVA was conducted with looking times as the dependent measure revealing a main effect for speaker’s voice, F (1,61) = 4.41, p < .05, and a main effect for syllabic change, F (1,61) = 8.94, p c .Ol. There was also an interaction effect for speaker X syllabic change, F (1, 6 1) = 4.47, p c .05, and familiarization voice X speaker X syllabic change, F (1, 61) = 5.22, pc .05. In short, these findings indicated that infants distinguished between the syllabic change and no-change trials in the novel voices; however, infants failed to respond differentially to the change versus no change in the familiar voice. Furthermore, infants showed a greater interest in novel syllabic changes when familiarized with a female voice and speech typical of infant directed speech. The results provide evidence that 1l-month-old infants are indeed capable of normalizing naturalistic speech which varies in multiple dimensions. However, it appears that this is a difficult task which requires large amounts of familiarization and is assisted by stimuli characteristic of infant-directed speech. These results also indicate that task difficulty affects infants’ ability to detect changes in linguistic stimuli. In sum, it appears that normalization of naturalistic speech is assisted by an initial representation of a sequence possessing the exaggerated and attention holding properties typical of infant directed speech.