Two experiments are described which explore the relationship between parental reports of infants' receptive vocabularies at 1 ; 6 (Experiment 1a) or 1 ; 3, 1 ; 6 and 1 ; 9 (Experiment 1b) and the comprehension infants demonstrated in a preferential looking task. The instrument used was the Oxford CDI, a British English adaptation of the MacArthur-Bates CDI (Words & Gestures). Infants were shown pairs of images of familiar objects, either both name-known or both name-unknown according to their parent's responses on the CDI. At all ages, and on both name-known and name-unknown trials, preference for the target image increased significantly from baseline when infants heard the target's label. This discrepancy suggests that parental report underestimates infants' word knowledge.

Lack of vision is associated with delayed early-object manipulative abilities and concepts; 'form' vision appeared to support early developmental advance. This paper provides baseline characteristics for cross-sectional and longitudinal follow-up investigations in progress. A methodological strength of the study was the representativeness of the cohort according to national epidemiological and population census data.

Aim To investigate the effects of home‐based early intervention in children with severe visual impairment (SVI) using the Developmental Journal for babies and young children with visual impairment (DJVI). Method A longitudinal observational study was undertaken with a national cohort (OPTIMUM) of infants with congenital disorders of the peripheral visual system (CDPVS) and profound‐SVI; and followed up after 12 months and 24 months. Intervention was categorized according to the practitioner diary records of their usual practice over 12 months from baseline comparing those receiving the DJVI and those receiving ‘Other Support’. Outcome measures of cognition and language, behaviour difficulties, parenting stress, and satisfaction with parent–practitioner partnership were collected. Results In the 54 children (26 males, 28 females, baseline mean age 13.5mo, SD 2.3mo, range 8–17mo) with ‘total’ CDPVS (including 16 ‘complex’ and 38 ‘simple’ with or without known brain disorder respectively), linear mixed effects pointed towards acceleration in sensorimotor understanding and expressive language especially in the ‘simple’ subsample (11.72 developmental quotient, 95% confidence interval −1.17 to 24.61, p>0.05) in those receiving the DJVI. Vision level also predicted outcomes (p<0.05). The DJVI group showed improvements in behavioural withdrawal (η2=0.20, p=0.02, ‘simple’) and parenting stress (d=0.78, d=0.92, p=0.02 total and ‘simple’ respectively) and perceived practitioner–parent relationship (η2=0.16, p=0.01). Interpretation Infants and young children with visual impairment receiving home‐based early intervention using the DJVI with a structured developmental approach had better outcomes than those receiving ‘other’ home‐based early interventions. Moderate to large effect improvements were found in child cognition and language, behaviour and parenting stress and the perceived practitioner‐parent relationship, although cognition did not reach 5% significance level. What this paper adds Early intervention using the Developmental Journal for babies and young children with visual impairment was associated with enhanced developmental outcomes compared to other approaches. Improvements were also found in child behaviour, parenting stress, and perceived parent practitioner outcomes. Type and complexity of visual impairment also influenced outcomes.

Research on imitation in infancy has primarily focused on what and when infants imitate. More recently, however, the question why infants imitate has received renewed attention, partly motivated by the finding that infants sometimes selectively imitate the actions of others and sometimes faithfully imitate, or overimitate, the actions of others. The present study evaluates the hypothesis that this varying imitative behavior is related to infants' social traits. To do so, we assessed faithful and selective imitation longitudinally at 12 and 15 months, and extraversion at 15 months. At both ages, selective imitation was dependent on the causal structure of the act. From 12 to 15 months, selective imitation decreased while faithful imitation increased. Furthermore, infants high in extraversion were more faithful imitators than infants low in extraversion. These results demonstrate that the onset of faithful imitation is earlier than previously thought, but later than the onset of selective imitation. The observed relation between extraversion and faithful imitation supports the hypothesis that faithful imitation is driven by the social motivations of the infant. We call this relation the King Louie Effect: like the orangutan King Louie in The Jungle Book, infants imitate faithfully due to a growing interest in the interpersonal nature of interactions.

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Mothers of infants with visual impairment are at increased risk of parenting stress. Parenting stress was higher in mothers of children with profound visual impairment than those with severe visual impairment. High levels of parenting stress and lower infant vision at 1 year of age predicted higher parenting stress at 2 years of age.

In the present article, we introduce the continuous unified electronic (CUE) diary method, a longitudinal, event-based, electronic parent report method that allows real-time recording of infant and child behavior in natural contexts. Thirty-nine expectant mothers were trained to identify and record target behaviors into programmed handheld computers. From birth to 18 months, maternal reporters recorded the initial, second, and third occurrences of seven target motor behaviors: palmar grasp, rolls from side to back, reaching when sitting, pincer grip, crawling, walking, and climbing stairs. Compliance was assessed as two valid entries per behavior: 97 % of maternal reporters met compliance criteria. Reliability was assessed by comparing diary entries with researcher assessments for three of the motor behaviors: palmar grasp, pincer grip and walking. A total of 81 % of maternal reporters met reliability criteria. For those three target behaviors, age of emergence was compared across data from the CUE diary method and researcher assessments. The CUE diary method was found to detect behaviors earlier and with greater sensitivity to individual differences. The CUE diary method is shown to be a reliable methodological tool for studying processes of change in human development.

Aim To investigate detection vision development in infants and toddlers with congenital disorders of the peripheral visual system (CDPVS) and severe to profound visual impairment (SVI/PVI). Method This was a longitudinal observational investigation of a cohort of infants with CDPVS (entry age 8–16mo) followed up 12 months later. Detection vision (Near Detection Scale [NDS]) and resolution acuity (Keeler Acuity Cards [KAC]) were assessed at each time point. Relationships between detection vision, resolution acuity, and age were investigated. Results The study cohort comprised 80 children (39 females, 41 males), mean age 13 months (Time 1) and 26 months (Time 2); 22 (27.5%) with PVI (light perception at best) and 58 (72.5%) with SVI (basic ‘form’ vision) at Time 1. All children achieved a measure with the NDS, however only 35 per cent and 56 per cent at Time 1 and Time 2 respectively did so on KAC. Those with PVI at Time 1 showed no further improvement at Time 2, but 87 per cent of children with SVI showed improvement in vision. The median change in NDS score was 1.0 (range 1–7, SD 1.68). Interpretation Vision development continues after 12 months of age in many toddlers if they have basic ‘form’ vision. A measure of detection vision is feasible in very young children when resolution acuity measurement is not achievable. What this paper adds The Near Detection Scale (NDS) can measure low levels of vision when acuity is not otherwise measurable. Vision can improve in toddlers with severe visual impairment who have some ‘form’ vision. Infants with light perception at best by 12 months are unlikely to show improvement in vision. There is a moderate negative relationship between the NDS and resolution acuity results.