Reduced perceptual narrowing in synesthesia.

Synesthesia is a neurologic trait in which specific inducers, such as sounds, automatically elicit additional idiosyncratic percepts, such as color (thus "colored hearing"). One explanation for this trait-and the one tested here-is that synesthesia results from unusually weak pruning of cortical synaptic hyperconnectivity during early perceptual development. We tested the prediction from this hypothesis that synesthetes would be superior at making discriminations from nonnative categories that are normally weakened by experience-dependent pruning during a critical period early in development-namely, discrimination among nonnative phonemes (Hindi retroflex /d̪a/ and dental /ɖa/), among chimpanzee faces, and among inverted human faces.

Beyond neonatal imitation: Aerodigestive stereotypies, speech development, and social interaction in the extended perinatal period.

In our target article, we argued that the positive results of neonatal imitation are likely to be by-products of normal aerodigestive development. Our hypothesis elicited various responses on the role of social interaction in infancy, the methodological issues about imitation experiments, and the relation between the aerodigestive theory and the development of speech. Here we respond to the commentaries.

The prevalence of synaesthesia depends on early language learning.

According to one theory, synaesthesia develops, or is preserved, because it helps children learn. If so, it should be more common among adults who faced greater childhood learning challenges. In the largest survey of synaesthesia to date, the incidence of synaesthesia was compared among native speakers of languages with transparent (easier) and opaque (more difficult) orthographies.

Neonatal imitation in context: Sensorimotor development in the perinatal period.

More than 35 years ago, Meltzoff and Moore (1977) published their famous article, "Imitation of facial and manual gestures by human neonates." Their central conclusion, that neonates can imitate, was and continues to be controversial. Here, we focus on an often-neglected aspect of this debate, namely, neonatal spontaneous behaviors themselves.

Color constancy for an unseen surface.

The illumination of a scene strongly affects our perception of objects in that scene, e.g., the pages of a book illuminated by candlelight will appear quite yellow relative to other types of artificial illuminants.

Synesthesia and learning: a critical review and novel theory.

Learning and synesthesia are profoundly interconnected. On the one hand, the development of synesthesia is clearly influenced by learning. Synesthetic inducers - the stimuli that evoke these unusual experiences - often involve the perception of complex properties learned in early childhood, e.

Grapheme-color synaesthesia benefits rule-based Category learning.

Researchers have long suspected that grapheme-color synaesthesia is useful, but research on its utility has so far focused primarily on episodic memory and perceptual discrimination. Here we ask whether it can be harnessed during rule-based Category learning. Participants learned through trial and error to classify grapheme pairs that were organized into categories on the basis of their associated synaesthetic colors.

Second-order mappings in grapheme-color synesthesia.

Typically, the search for order in grapheme-color synesthesia has been conducted by looking at the frequency of certain letter-color associations. Here, we report stronger associations when second-order similarity mappings are examined--specifically, mappings between the synesthetic colors of letters and letter shape, frequency, and position in the alphabet. The analyses demonstrate that these relations are independent of one other.