3.4 Sensory dominance is observed in childhood

[The second in a series of 3 excerpts re sensory integration from my book, Ready to Learn.]

Objectives:

A. Learn that animal and human studies reveal that immature perceivers often rely on a dominant sensory input to guide task-related behaviour.

B. Understand that sensory dominance in a particular context can change as part of normal development.

When a perceiver in a multisensory task must decide upon a task-appropriate action, experience routinely assigns a weighted reliability to each of the sensory inputs deemed to be relevant. Combining (integrating) those weighted inputs can then yield well documented multisensory benefits, informing a behavioural response that is measurably stronger, faster, and more reliable than that which any of the contributing inputs could provide on their own.

The adult participants in the Nardini and colleagues (2008) darkened room study outperformed the children for one simple reason. The adults had more experience integrating sensory cues to deal with navigational uncertainty. While the children could only draw on the cues of one sensory system at a time, the adults were using visual and vestibular cues that had each been weighted for reliability. Their more mature strategy allowed the adults to lower the variability of their estimations and more accurately return an object to its original location.

Acquiring the full advantage of multisensory integration requires time and suitable experience, and the breadth of sensory interactions seen along that path is not fully understood. In one scenario that is often seen during child development, sensory information from one modality may provide little corroborating information to another modality. When this occurs, the more valuable (task relevant) input will dominate and suppress processing of the other (see Barnhart, 2018; Robinson et al., 2020).

In animals, sensory dominance frequently occurs. For instance, Johnston and Gottlieb (1981, 1985) observed that the developing sensory systems of mallard hatchlings do not operate on an “equal footing.” Hatchlings typically experience both auditory and visual stimulation following hatching but “prefer” to use auditory cues over visual cues to find their mother. The authors concluded that hatchlings ignore visual cues altogether during the first two days of life and will only use dominant auditory cues unless those cues are unavailable or unclear (Johnston & Gottlieb, 1985). Only at three days of age and with typical experience will ducklings begin to prefer visual cues over auditory cues when both are available. Lickliter and Virkar (1989) made similar observations with quail chicks.

In humans, sensory dominance has been used to explain a developmental change we see in the relationship between vision and hearing. Specifically, adults have no difficulty when asked to look at a computer screen and press one button upon seeing a light and another button upon hearing a tone. On the other hand, if the light and tone sometimes occur together and participants are asked to press the button for the first stimulus they recognize, we begin to see surprising errors. Even when the light and tone occur at the same time, participants are much more likely to respond as if the light had occurred first, and many will later report they had not even heard the tone. In short, the visual light dominates the auditory tone. This phenomenon was named the “Colavita effect” after Francis B. Colavita, the researcher who discovered it (Colavita, 1974). Since then, other researchers have consistently observed the effect in many variations of the original experiment.

However, more recent studies have failed to find the Colavita effect in early childhood. In fact, the evidence suggests something very different. Young children, especially infants, show a strong auditory dominance that gradually shifts during development to the visual dominance we see in adulthood.