In this article, the authors introduce a new theoretical framework for understanding intersensory development. Their approach is based upon insights gained from adults who experience synesthesia, in whom sensory stimuli induce extra cross-modal or intramodal percepts. Synesthesia appears to represent one way that typical developmental mechanisms can play out by magnifying connections present in early life that are pruned and/or inhibited during development but persist in muted form in all adults. As such, the study of synesthesia provides valuable insights into the nature of intersensory development. The authors review evidence on the perceptual reality and neural basis of synesthesia, then summarize developmental models and evidence that its underlying mechanisms are universal in adults. They illustrate how evidence for consistent sensory associations in adults leads to predictions about toddlers' perception and present 3 bodies of work that have confirmed those hypotheses. They end by describing novel hypotheses about intersensory development that arise from this framework. Such intersensory associations appear to reflect intrinsic sensory cortical organization that influences the development of perception and of language and that may constrain the learning of environmentally based associations.
In this article, the authors introduce a new theoretical framework for understanding intersensory development. Their approach is based upon insights gained from adults who experience synesthesia, in whom sensory stimuli induce extra cross-modal or intramodal percepts. Synesthesia appears to represent one way that typical developmental mechanisms can play out by magnifying connections present in early life that are pruned and/or inhibited during development but persist in muted form in all adults. As such, the study of synesthesia provides valuable insights into the nature of intersensory development. The authors review evidence on the perceptual reality and neural basis of synesthesia, then summarize developmental models and evidence that its underlying mechanisms are universal in adults. They illustrate how evidence for consistent sensory associations in adults leads to predictions about toddlers' perception and present 3 bodies of work that have confirmed those hypotheses. They end by describing novel hypotheses about intersensory development that arise from this framework. Such intersensory associations appear to reflect intrinsic sensory cortical organization that influences the development of perception and of language and that may constrain the learning of environmentally based associations.
Many letters of the alphabet are consistently mapped to specific colours by English-speaking adults, both in the general population and in individuals with grapheme-colour synaesthesia who perceive letters in colour. Such associations may be naturally biased by intrinsic sensory cortical organisation, or may be based in literacy (eg 'A' is for 'apple', apples are red; therefore A is red). To distinguish these two hypotheses, we tested pre-literate children in three experiments and compared their results to those of literate children (aged 7-9 years) and adults. The results indicate that some colour letter mappings (O white, X black) are naturally biased by the shape of the letter, whereas others (A red, G green) may be based in literacy. They suggest that sensory cortical organisation initially binds colour to some shapes, and that learning to read can induce additional associations, likely through the influence of higher-order networks as letters take on meaning.
Many letters of the alphabet are consistently mapped to specific colors in English-speaking adults, both in the general population and in individuals with grapheme-color synaesthesia who perceive letters in color. Here, across six experiments, we tested the ubiquity of the color/letter associations with typically developing toddlers, literate children, and adults. We found that pre-literate children associate O with white and X with black and discovered that they also associate I and ameboid nonsense shapes with white; Z and jagged nonsense shapes with black; and C with yellow; but do not make a number of other associations (B blue; Y yellow; A red; G green) seen in literate children and adults. The toddlers' mappings were based on the shape and not the sound of the letter. The results suggest that sensory cortical organization initially binds specific colors to some specific shapes and that learning to read can induce additional associations, likely through the influence of higher order networks as letters take on meaning.
The purpose of this study was to document colour and texture associations to odours using a variety of odours including both pleasant and unpleasant odours, some of which were likely to be unfamiliar. We asked non-synaesthetic adults (n = 78) to make colour and shape/texture associations to 22 odours. A subset of the participants (/i = 41) smelled the odours a second time in order to identify them. Each odour stimulus was associated consistently to one or more specific colours and/or textures (all p's < O.OI by binomial probability statistics). Associations to the four odours that were identified accurately (cinnamon, lemon, peppermint and licorice) seemed to be based on learning/memory (e.g. lemon = yellow). The associations to the 18 odours that were not identified accurately are less likely to be based on learning/memory (e.g. ginger = black, rough, sharp; lavender = green, white, liquid, sticky). We speculate that sensory associations to odours, like those to pitch and letters (e.g. Mondloch and Maurer, 2004;Spector and Maurer, 2008), may result from the joint infiuence of learning and natural biases linking dimensions across sensory systems. Such links may refiect inherent neural organization that is modifiable with learning and that can manifest as cross-modal associations or synaesthetic percepts.
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