Publisher Correction: Five-month-old infants detect affiliation in colaughter.

An amendment to this paper has been published and can be accessed via a link at the top of the paper

Is Visual Perceptual Narrowing an Obligatory Developmental Process?

Perceptual narrowing, or a diminished perceptual sensitivity to infrequently encountered stimuli, sometimes accompanied by an increased sensitivity to frequently encountered stimuli, has been observed in unimodal speech and visual perception, as well as in multimodal perception, leading to the suggestion that it is a fundamental feature of perceptual development. However, recent findings in unimodal face perception suggest that perceptual abilities are flexible in development. Similarly, in multimodal perception, new paradigms examining temporal dynamics, rather than standard overall looking time, also suggest that perceptual narrowing might not be obligatory. Across two experiments, we assess perceptual narrowing in unimodal visual perception using remote eye-tracking. We compare adults’ looking at human faces and monkey faces of different species, and present analyses of standard overall looking time and temporal dynamics. As expected, adults discriminated between different human faces, but, unlike previous studies, they also discriminated between different monkey faces. Temporal dynamics revealed that adults more readily discriminated human compared to monkey faces, suggesting a processing advantage for conspecifics compared to other animals. Adults’ success in discriminating between faces of two unfamiliar monkey species calls into question whether perceptual narrowing is an obligatory developmental process. Humans undoubtedly diminish in their ability to perceive distinctions between infrequently encountered stimuli as compared to frequently encountered stimuli, however, consistent with recent findings, this narrowing should be conceptualized as a refinement and not as a loss of abilities. Perceptual abilities for infrequently encountered stimuli may be detectable, though weaker compared to adults’ perception of frequently encountered stimuli. Consistent with several other accounts we suggest that perceptual development must be more flexible than a perceptual narrowing account posits

Are the Products of Statistical Learning Abstract or Stimulus-Specific?

Learners can segment potential lexical units from syllable streams when statistically variable transitional probabilities between adjacent syllables are the only cues to word boundaries. Here we examine the nature of the representations that result from statistical learning by assessing learners’ ability to generalize across acoustically different stimuli. In three experiments, we compare two possibilities: that the products of statistical segmentation processes are abstract and generalizable representations, or, alternatively, that products of statistical learning are stimulus-bound and restricted to perceptually similar instances. In Experiment 1, learners segmented units from statistically predictable streams, and recognized these units when they were acoustically transformed by temporal reversals. In Experiment 2, learners were able to segment units from temporally reversed syllable streams, but were only able to generalize in conditions of mild acoustic transformation. In Experiment 3, learners were able to recognize statistically segmented units after a voice change but were unable to do so when the novel voice was mildly distorted. Together these results suggest that representations that result from statistical learning can be abstracted to some degree, but not in all listening conditions

Is speech special? : insights from neonates and neuroimaging

Language is a uniquely human adaptation that is hypothesised to require specialised anatomical substrates and dedicated processing mechanisms. Speech, the primary medium for language, is argued to rely on specialised substrates and processing as well. Yet, to date, evidence for the speech specialisation hypothesis has been equivocal. The four experiments in this thesis aim to advance the discussion in two ways. The differential processing of speech by humans was investigated through the use of functional neuroimaging tools (Experiment One), and through developmental studies of young infants' listening biases (Experiments Two-Four). In Experiment One, functional neuroimaging tools are used to investigate the specificity of neural substrates recruited in detecting speech compared with closely matched non-speech controls. This study takes advantage of an event-related imaging design that provides a narrow window of observation for neural recruitment during individual stimulus events. The results of the first study demonstrate that adults activate specific neural substrates when detecting speech sounds, indicating that specialised substrates are involved from the early processing stages. Experiments Two through Four take an ethological approach to speech specialisation and investigate whether young infants show a bias for listening to speech as compared to matched non-speech sounds. In Experiment Two, behavioural methods probe whether young infants of 2 to 7 months show listening preferences for speech compared with non-speech. Experiment Three seeks to establish the roots of a speech bias in the neonatal period. Finally, Experiment Four investigates the origin of the bias, to determine whether the speech bias originates from prenatal experience, or is independent of specific experience. The results of these studies show that differential processing has its roots in early infancy, with infants demonstrating a preference for listening to speech from birth. The speech bias shown by neonates appears not to be based on specific experience with speech sounds, but instead is rooted in human biology. Human infants are prewired to preferentially attend to speech, granting speech a special status in relation to other sounds.Medicine, Faculty ofGraduat