Increasing Task Difficulty Enhances Effects of Intersensory Redundancy: Testing a New Prediction of the Intersensory Redundancy Hypothesis


Infants can detect information that is common and redundantly across the senses. This information includes temporal synchrony (most fundamental amodal property), rhythm, tempo, and changing intensity, all of which are labeled amodal (meaning not specific to a particular sense modality). Amodal information are considering “building blocks” of perceptual development and facilitate perception of unitary multimodal events and are the “gatekeeper” to processes an event as a whole. To explain selective attention, Bahrick and Lickliter proposed the Intersensory Redundancy Hypothesis (IRH), which states that intersensory redundancy is highly salient and directs selective attention to amodal aspects of events that are redundantly specified across senses. It makes three predictions, with a forth being proposed and tested in this new study.

The fourth prediction of the IRH states that intersensory facilitation occurs in the presence of tasks of relatively high difficulty to a person in terms of perception. In early development, infants have limited attentional resources, making perceptual processing difficult. Perceptual learning occurs throughout a person’s lifetime, which means intersensory facilitation should be present in later development when perceivers need to learn how to perceive finer distinctions in stimuli (learning a new language, playing an instrument).  As infants grow older, they have more attentional resources and increased perceptual differentiation. The more difficult a task difficulty is, the more differentiation is needed, reverting older infants to use patterns of intersensory facilitation seen in younger infants. They are expected to show better detection of amodal properties in bimodal, redundant stimulation than in unimodal, nonredundant stimulation.

Results of the study confirmed predictions, finding that infants who receive tempo contrasts of high difficult showed intersensory facilitation. Infants given tempo contrasts of low and moderate difficult showed discrimination in both conditions. Findings suggest that discrimination is key in task difficultly, and supports the prediction that as tasks get more difficult, older and more experienced infants show patterns of intersensory facilitation shown by younger infants.


Bahrick, L. E., Lickliter, R., Castellanos, I., Vaillant-Molina, M. (2010). Increasing task difficulty enhances effects of intersensory redundancy: Testing a new prediction of the intersensory redundancy hypothesis. Developmental Science13(5), 731–737. doi: 10.1111/j.1467-7687.2009.00928.x


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