Low working memory capacity impedes both efficiency and learning of number transcoding in children

This study aimed to evaluate the impact of individual differences in working memory capacity on number transcoding. A recently proposed model, ADAPT (a developmental asemantic procedural transcoding model), accounts for the development of number transcoding from verbal form to Arabic form by two mechanisms: the learning of new production rules that enlarge the range of numbers a child can transcode and the increase of the mental lexicon. The working memory capacity of 7-year-olds was evaluated along with their ability to transcode one- to four-digit numbers. As ADAPT predicts, the rate of transcoding errors increased when more production rules were required and when children had low working memory capacity, with these two factors interacting. Moreover, qualitative analysis of the errors produced by high- and low-span children showed that the latter have a developmental delay in the acquisition of the production rules.     

Sensed presence as a correlate of sleep paralysis distress, social anxiety and waking state social imagery

Isolated sleep paralysis (ISP) is a common parasomnia characterized by an inability to move or speak and often accompanied by hallucinations of a sensed presence nearby. Recent research has linked ISP, and sensed presence more particularly, with social anxiety and other psychopathologies. The present study used a large sample of respondents to an internet questionnaire (N=193) to test whether these associations are due to a general personality factor, affect distress, which is implicated in nightmare suffering and hypothesized to involve dysfunctional social imagery processes. A new measure, ISP distress, was examined in relation to features of ISP experiences, to self-reported psychopathological diagnosis, to scores on the Leibowitz Social Anxiety Scale and to scores on a new questionnaire subscale assessing social imagery in a variety of waking states. Three main results were found: (1) ISP experiences are only weakly associated with a prior diagnosis of mental disorder, (2) sensed presence during ISP is associated preferentially with ISP distress, and (3) ISP distress is associated with dysfunctional social imagery. A general predisposition to affective distress may influence the distress associated with ISP experiences; overly passive social imagery may, in turn, be implicated in this affect distress influence.     

Design of randomized controlled trials: Principles and methods applied to a treatment for early stuttering

The “gold standard” methodology for treatment efficacy research is the randomized controlled trial (RCT), which is used extensively in medical research and in other areas such as psychology. Results from a well designed and conducted RCT, which show a new treatment to be clinically and statistically superior to current standard practice, can lead to a change in clinical practice. This paper presents a tutorial on RCTs, presenting and discussing the following principles and methods: the trial protocol, choice of control treatment, eligibility criteria, random allocation, outcomes and hypotheses, sample size, subject recruitment, analysis by intention to treat, interim analysis, stopping rules, safety data monitoring/trial management, and study documentation. RCTs are a complicated and logistically involved methodology. Hence, prior to the commitment of resources to such a trial in the development of a new treatment, the safety and clinical promise of the new treatment needs to be demonstrated with preliminary studies. Such preliminary studies have been completed for the Lidcombe Program (LP) of early stuttering intervention, and an RCT of that treatment is being conducted at the time of writing. The principles and methods of RCTs are illustrated with reference to that study.

Educational objectives: The reader will understand the design principles and methods of RCTs. The reader will understand the logistics of conducting a RCT of a treatment for early stuttering.     

Cognitive processing impairments in a supra-second temporal discrimination task in rats with cerebellar lesion

The role of interpositus nuclei (IN) in timing in the sub-second range is well supported in eyeblink conditioning studies. Timing impairments shown in the seconds range in patients with intermediate cerebellar lesion, and known intermediate cerebellar cortex projection to IN raise the question of a possible involvement of IN in timing in the supra-second range as well. To address this question, we tested rats (Sprague-Dawley) given bilateral lesions of IN with Colchicine in a 2- vs. 8-s temporal discrimination task, followed by three daily sessions of a temporal bisection tests with five added intermediate non-reinforced durations. IN lesioned rats showed normal acquisition of the temporal discrimination, but a transient impairment of temporal sensitivity during the bisection tests. In addition, their response latencies suggested a different behavioral strategy from that of control animals. Our results indicate that the IN of the cerebellum may not be critically involved in temporal processing in the 2–8 s range, but may play a role in the cognitive processes that access temporal information in the mediation of choice behavior.     

Adaptive specialization in position encoding while learning to read

The present experiments focused on how orthographic processing develops during reading acquisition. Specifically, a large, cross‐sectional sample of children from grade 2 to grade 4 was exposed to pairs of words, pseudowords, digit strings, and pseudo‐letter (Armenian) strings while their sensitivity to transpositions (T) and substitutions (S) of internal characters was investigated in a perceptual matching task. The results showed that the development of identity and position decoding diverged between the four stimulus categories. Most importantly, sensitivity improved with longer exposure to formal education and higher reading level to both S and T pairs for digit strings, but only to S pairs for words and pseudowords. The results were successfully reproduced in two small independent samples. We propose a general framework, the Adaptive Specialization Hypothesis, to accommodate the results. According to this hypothesis, the transposed‐letter effect is not a hard‐wired feature of the orthographic processing system but an adaptive response of the developing orthographic system to the constraints of lexical access in several orthographies.     

Controlled processes account for age-related decrease in episodic memory

A decrease in controlled processes has been proposed to be responsible for age-related episodic memory decline. We used the Process Dissociation Procedure, a method that attempts to estimate the contribution of controlled and automatic processes to cognitive performance, and entered both estimates in regression analyses. Results indicate that only controlled processes explained a great part of the age-related variance in a word recall task, especially when little environmental support was offered.     

Invisible displacement understanding in domestic dogs (<Emphasis Type="Italic">Canis familiaris</Emphasis>): the role of visual cues in search behavior

Recently, (Collier-Baker E, Davis JM, Suddendorf T (2004) J Comp Psychol 118:421–433) suggested that domestic dogs do not understand invisible displacements. In the present study, we further investigated the hypothesis that the search behavior of domestic dogs in invisible displacements is guided by various visual cues inherent to the task rather than by mental representation of an object’s past trajectory. Specifically, we examined the role of the experimenter as a function of the final position of the displacement device in the search behavior of domestic dogs. Visible and invisible displacement problems were administered to dogs (N = 11) under two conditions. In the Visible-experimenter condition, the experimenter was visible whereas in the Concealed-experimenter condition, the experimenter was visibly occluded behind a large rigid barrier. Our data supported the conclusion that dogs do not understand invisible displacements but primarily search as a function of the final position of the displacement device and, to a lesser extent, the position of the experimenter.     

Deficit in phonological processes: a characteristic of the neuropsychological profile of children with NF1

Learning disabilities are one of the most frequent complications of neurofibromatosis type 1 (NF1) in children. Studies of the effects of the neurocognitive deficit on academic performance are relatively rare, owing to the small size of the populations concerned. However, research is needed to develop effective rehabilitation programs. In the present study, we explored the impact of a possible phonological deficit on the reading abilities of children with NF1. A multicenter, cross-sectional study was conducted in France on two groups of 75 children with or without NF1 aged 8–12 years, matched for age, sex, handedness, and reading level. All participants underwent a neuropsychological evaluation to assess their general cognitive level, reading skills, phonological processes, visuoperceptual abilities, and attentional capacity. Phonological skills were assessed by means of two phonological awareness tasks and one short-term memory task. In the group of children with NF1, 41% had reading difficulties. Phonological processes were impaired in this group, compared with the children without NF1. Similar differences were found for a phoneme deletion task after adjustment for reading difficulties, IQ level, and visuoperceptual abilities. Phonological awareness, but not phonological short-term memory, was impaired in children with NF1, and not just those whose reading was impaired. Results suggest that children with NF1 have a phonological awareness deficit, whatever their reading level. Identification of reduced phonological skills may warrant the implementation of a specific rehabilitation program before early reading difficulties emerge.