Abstract
BackgroundPerceived spatial intervals between successive flashes can be distorted by varying the temporal intervals between them (the “tau effect”). A previous study showed that a tau effect for visual flashes could be induced when they were accompanied by auditory beeps with varied temporal intervals (an audiovisual tau effect).Methodology/Principal FindingsWe conducted two experiments to investigate whether the audiovisual tau effect occurs in infancy. Forty-eight infants aged 5–8 months took part in this study. In Experiment 1, infants were familiarized with audiovisual stimuli consisting of three pairs of two flashes and three beeps. The onsets of the first and third pairs of flashes were respectively matched to those of the first and third beeps. The onset of the second pair of flashes was separated from that of the second beep by 150 ms. Following the familiarization phase, infants were exposed to a test stimulus composed of two vertical arrays of three static flashes with different spatial intervals. We hypothesized that if the audiovisual tau effect occurred in infancy then infants would preferentially look at the flash array with spatial intervals that would be expected to be different from the perceived spatial intervals between flashes they were exposed to in the familiarization phase. The results of Experiment 1 supported this hypothesis. In Experiment 2, the first and third beeps were removed from the familiarization stimuli, resulting in the disappearance of the audiovisual tau effect. This indicates that the modulation of temporal intervals among flashes by beeps was essential for the audiovisual tau effect to occur (Experiment 2).Conclusions/SignificanceThese results suggest that the cross-modal processing that underlies the audiovisual tau effect occurs even in early infancy. In particular, the results indicate that audiovisual modulation of temporal intervals emerges by 5–8 months of age.
Highlights
IntroductionWe addressed the issue of whether the perceptual system of 5- to 8-month-old infants is able to construct audiovisual events by arbitrarily integrating auditory and visual information across space and time
On the other hand, when the first temporal interval between B1 and B2 was longer than the second temporal interval between B2 and B3, the first spatial interval between F1 and F2 was perceived to be longer than the second spatial interval between F2 and F3. This effect disappeared when B1 and B3 were withdrawn from the stimulus. These findings suggest that the audiovisual tau effect arises from the modulation of temporal intervals between flashes by those between concurrent beeps, not from the temporal capture occurring between F2 and B2
The t-test revealed that the difference in proportions between phases was significant (t(23) = 2.369, p,.027). These results indicate that infants’ preferences for the novel array were caused after habituation to the stimuli in the familiarization phase. These results indicate that perceived spatial intervals between the pairs of flashes in the familiarization phase were distorted for the infants, resulting in a preference for the novel array in the test phase
Summary
We addressed the issue of whether the perceptual system of 5- to 8-month-old infants is able to construct audiovisual events by arbitrarily integrating auditory and visual information across space and time. It has been found that infants are able to detect temporal concurrency of audiovisual information [1,2,3], and to match intensity across information [4]. It has been suggested that these data may reflect the detection of amodal equivalence of signals perceived through several input modalities. It has been shown in two studies [6,7] that infants are able to detect equivalence in temporal congruency or intensity. A previous study showed that a tau effect for visual flashes could be induced when they were accompanied by auditory beeps with varied temporal intervals (an audiovisual tau effect)
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