Mothers speak differently to infants at‐risk for dyslexia

Dyslexia is a neurodevelopmental disorder manifested in deficits in reading and spelling skills that is consistently associated with difficulties in phonological processing. Dyslexia is genetically transmitted, but its manifestation in a particular individual is thought to depend on the interaction of epigenetic and environmental factors. We adopt a novel interactional perspective on early linguistic environment and dyslexia by simultaneously studying two pre‐existing factors, one maternal and one infant, that may contribute to these interactions; and two behaviours, one maternal and one infant, to index the effect of these factors. The maternal factor is whether mothers are themselves dyslexic or not (with/without dyslexia) and the infant factor is whether infants are at‐/not‐at family risk for dyslexia (due to their mother or father being dyslexic). The maternal behaviour is mothers’ infant‐directed speech (IDS), which typically involves vowel hyperarticulation, thought to benefit speech perception and language acquisition. The infant behaviour is auditory perception measured by infant sensitivity to amplitude envelope rise time, which has been found to be reduced in dyslexic children. Here, at‐risk infants showed significantly poorer acoustic sensitivity than not‐at‐risk infants and mothers only hyperarticulated vowels to infants who were not at‐risk for dyslexia. Mothers’ own dyslexia status had no effect on IDS quality. Parental speech input is thus affected by infant risk status, with likely consequences for later linguistic development.     

Spatial numerical associations in preschoolers

ABSTRACT

Three-to-five-year-old French children were asked to add or remove objects to or from linear displays. The hypothesis of a universal tendency to represent increasing number magnitudes from left to right led to predict a majority of manipulations at the right end of the rows, whatever children's hand laterality. Conversely, if numbers are not inherently associated with space, children were expected to favour laterality-consistent manipulations. The results showed a strong tendency to operate on the right end of the rows in right-handers, but no preference in left-handers. These findings suggest that the task elicited a left-to-right oriented representation of magnitudes that counteracted laterality-related responses in left-handed children. The young age of children and the lack of a developmental trend towards right preference weaken the hypothesis of a cultural origin of this oriented representation. The possibility that our results are due to weaker brain lateralisation in left-handers compared to right-handers is addressed in Discussion section.     

TreeBUGS: An R package for hierarchical multinomial-processing-tree modeling

Multinomial processing tree (MPT) models are a class of measurement models that account for categorical data by assuming a finite number of underlying cognitive processes. Traditionally, data are aggregated across participants and analyzed under the assumption of independently and identically distributed observations. Hierarchical Bayesian extensions of MPT models explicitly account for participant heterogeneity by assuming that the individual parameters follow a continuous hierarchical distribution. We provide an accessible introduction to hierarchical MPT modeling and present the user-friendly and comprehensive R package TreeBUGS, which implements the two most important hierarchical MPT approaches for participant heterogeneity—the beta-MPT approach (Smith & Batchelder, Journal of Mathematical Psychology 54:167-183, 2010) and the latent-trait MPT approach (Klauer, Psychometrika 75:70-98, 2010). TreeBUGS reads standard MPT model files and obtains Markov-chain Monte Carlo samples that approximate the posterior distribution. The functionality and output are tailored to the specific needs of MPT modelers and provide tests for the homogeneity of items and participants, individual and group parameter estimates, fit statistics, and within- and between-subjects comparisons, as well as goodness-of-fit and summary plots. We also propose and implement novel statistical extensions to include continuous and discrete predictors (as either fixed or random effects) in the latent-trait MPT model.     

Normative accuracy and response time data for the computerized Benton Facial Recognition Test (BFRT-<Emphasis Type="Italic">c</Emphasis>)

We report normative data from a large (N = 307) sample of young adult participants tested with a computerized version of the long form of the classical Benton Facial Recognition Test (BFRT; Benton & Van Allen, 1968). The BFRT-c requires participants to match a target face photograph to either one or three of six face photographs presented simultaneously. We found that the percent accuracy on the BFRT-c (81%–83%) was below ceiling yet well above chance level, with little interindividual variance in this typical population sample, two important aspects of a sensitive clinical test. Although the split-half reliability on response accuracy was relatively low, due to the large variability in difficulty across items, the correct response times measured in this version—completed in 3 min, on average—provide a reliable and critical complementary measure of performance at individual unfamiliar-face matching. In line with previous observations from other measures, females outperformed male participants at the BFRT-c, especially for female faces. In general, performance was also lower following lighting changes than following head rotations, in line with previous studies that have emphasized participants’ limited ability to match pictures of unfamiliar faces with important variations in illumination. Overall, this normative data set supports the validity of the BFRT-c as a key component of a battery of tests to identify clinical impairments in individual face recognition, such as observed in acquired prosopagnosia. However, this analysis strongly recommends that researchers consider the full test results: Beyond global indexes of performance based on accuracy rates only, they should consider the time taken to match individual faces as well as the variability in performance across items.     

Object-centred spatial reference in 4-month-old infants

An appreciation of object-centred spatial relations involves representing a 'within-object' spatial relation across changes in the object orientation. This representational ability is important in adult object recognition [Biederman, I. (1987). Recognition-by-components: A theory of human image understanding. Psychological Review, 94, 115-147; Marr, D., & Nishihara, H. K. (1978). Representation and recognition of the spatial organisation of three-dimensional structure. Proceedings of the Royal Society of London, Series B (Biological Sciences), 200, 269-294; Tarr, M. J., & Pinker, S. (1990). When does human object recognition use a viewer-centred reference frame? Psychological Science, 1, 253-256] and is also thought to be a fundamental component of the mature object concept [Piaget, J. (1954). The Construction of Reality in the Child. Routledge & Kegan-Paul: London, UK. (Originally published in French in 1937)]. An experiment is reported in which eighteen 4-month-old infants were familiarised to a specific spatial relation within an object, across six different orientations of the object. On subsequent test trials the object was presented to the infants in an entirely novel orientation. Between successive test trials the within-object spatial relation was alternated between novel and familiar. The infants demonstrated significant sensitivity of their looking to both the novelty of the stimuli and the order in which novel and familiar stimuli were presented. It is concluded that by 4 months of age infants are able to form object-centred spatial frames of reference. These findings are discussed in the light of our current understanding of the development of object representation during infancy.