Young children combine sensory cues with learned information in a statistically efficient manner: But task complexity matters

Multisensory perception constrains the formation of object categories: a review of evidence from sensory-driven and predictive processes on categorical decisions

Although object categorization is a fundamental cognitive ability, it is also a complex process going beyond the perception and organization of sensory stimulation. Here we review existing evidence about how the human brain acquires and organizes multisensory inputs into object representations that may lead to conceptual knowledge in memory. We first focus on evidence for two processes on object perception, multisensory integration of redundant information (e.g. seeing and feeling a shape) and crossmodal, statistical learning of complementary information (e.g. the 'moo' sound of a cow and its visual shape). For both processes, the importance attributed to each sensory input in constructing a multisensory representation of an object depends on the working range of the specific sensory modality, the relative reliability or distinctiveness of the encoded information and top-down predictions. Moreover, apart from sensory-driven influences on perception, the acquisition of featural information across modalities can affect semantic memory and, in turn, influence category decisions. In sum, we argue that both multisensory processes independently constrain the formation of object categories across the lifespan, possibly through early and late integration mechanisms, respectively, to allow us to efficiently achieve the everyday, but remarkable, ability of recognizing objects. This article is part of the theme issue 'Decision and control processes in multisensory perception'.

Bayesian causal inference in visuotactile integration in children and adults

If cues from different sensory modalities share the same cause, their information can be integrated to improve perceptual precision. While it is well established that adults exploit sensory redundancy by integrating cues in a Bayes optimal fashion, whether children under 8 years of age combine sensory information in a similar fashion is still under debate. If children differ from adults in the way they infer causality between cues, this may explain mixed findings on the development of cue integration in earlier studies. Here we investigated the role of causal inference in the development of cue integration, by means of a visuotactile localization task. Young children (6-8 years), older children (9.5-12.5 years) and adults had to localize a tactile stimulus, which was presented to the forearm simultaneously with a visual stimulus at either the same or a different location. In all age groups, responses were systematically biased toward the position of the visual stimulus, but relatively more so when the distance between the visual and tactile stimulus was small rather than large. This pattern of results was better captured by a Bayesian causal inference model than by alternative models of forced fusion or full segregation of the two stimuli. Our results suggest that already from a young age the brain implicitly infers the probability that a tactile and a visual cue share the same cause and uses this probability as a weighting factor in visuotactile localization.