Developing Representations of Compound Stimuli

Classification based on multiple dimensions of stimuli is usually associated with similarity-based representations, whereas uni-dimensional classifications are associated with rule-based representations. This paper studies classification of stimuli and category representations in school-aged children and adults when learning to categorize compound, multi-dimensional stimuli. Stimuli were such that both similarity-based and rule-based representations would lead to correct classification. This allows testing whether children have a bias for formation of similarity-based representations. The results are at odds with this expectation. Children use both uni-dimensional and multi-dimensional classification, and the use of both strategies increases with age. Multi-dimensional classification is best characterized as resulting from an analytic strategy rather than from procedural processing of overall-similarity. The conclusion is that children are capable of using complex rule-based categorization strategies that involve the use of multiple features of the stimuli. The main developmental change concerns the efficiency and consistency of the explicit learning system

Cognitive flexibility training has direct and near transfer effects, but no far transfer effects, preschoolers

The current project studied the direct, near transfer, and far transfer effects of cognitive flexibility training in two experiments with 117 3-year-olds. In both Experiments 1 and 2, children performed three Dimensional Change Card Sorting (DCCS) tasks in a pre-training/training/post-training design. The training consisted of giving corrective feedback in the training DCCS task. In Experiment 2, in addition, three other executive control tasks were administered during pre-training and post-training. Results showed a direct effect of feedback in the training DCCS task and transfer of this effect to the post-training DCCS task after 1 week with different sorting rules and different stimuli. These findings show that preschoolers learned to switch sorting rules in the context of the DCCS task, independent of the specific sorting rules, and that this effect is not transient. No support was found for transfer to the other executive control tasks. A possible explanation is that the feedback mainly improved rule switching, an ability that is specifically required for performing a cognitive flexibility task but not the other executive control tasks

Children's Mental Models of Prenatal Development

Children's thinking about prenatal development requires reasoning about change that cannot be observed directly. How do children gain knowledge about this topic? Do children have mental models or is their knowledge fragmented? In Experiment 1, results of a forced-choice questionnaire about prenatal development (6- to 13-year-olds; N = 317) indicated that children do have a variety of coherent, grade-related, theories about early shape of the fetus, but not about bodily functions. Coherence of the mental models was enhanced by a preceding generative task. Children's mental models were in agreement with reasoning about natural transformations (Rosengren et al., 1991) and constraints in representational flexibility (Karmiloff-Smith, 1992). In Experiment 2, an open-question interview was administered (6- to 12-year-old children; N = 38). The interview resulted in grade-unrelated, incoherent responses. This study contributes to a deeper understanding of naïve biology and to the effects of different methodologies being used in the area of mental models

Pre-verbal infants perceive emotional facial expressions categorically

Adults perceive emotional expressions categorically, with discrimination being faster and more accurate between expressions from different emotion categories (i.e. blends with two different predominant emotions) than between two stimuli from the same category (i.e. blends with the same predominant emotion). The current study sought to test whether facial expressions of happiness and fear are perceived categorically by pre-verbal infants, using a new stimulus set that was shown to yield categorical perception in adult observers (Experiments 1 and 2). These stimuli were then used with 7-month-old infants (N  =  34) using a habituation and visual preference paradigm (Experiment 3). Infants were first habituated to an expression of one emotion, then presented with the same expression paired with a novel expression either from the same emotion category or from a different emotion category. After habituation to fear, infants displayed a novelty preference for pairs of between-category expressions, but not within-category ones, showing categorical perception. However, infants showed no novelty preference when they were habituated to happiness. Our findings provide evidence for categorical perception of emotional expressions in pre-verbal infants, while the asymmetrical effect challenges the notion of a bias towards negative information in this age group

Early growth response 1 regulates hematopoietic support and proliferation in human primary bone marrow stromal cells

Human bone marrow stromal cells (BMSC) are key elements of the hematopoietic environment and they play a central role in bone and bone marrow physiology. However, how key stromal cell functions are regulated is largely unknown. We analyzed the role of the immediate early response transcription factor EGR1 as key stromal cell regulator and found that EGR1 was highly expressed in prospectivelyisolated primary BMSC, down-regulated upon culture, and low in noncolony-forming CD45neg stromal cells. Furthermore, EGR1 expression was lower in proliferative regenerating adult and fetal primary cells compared to adult steady-state BMSC. Overexpression of EGR1 in stromal cells induced potent hematopoietic stroma support as indicated by an increased production of transplantable CD34+ CD90+ hematopoietic stem cells in expansion co-cultures. The improvement in bone marrow stroma support function was mediated by increased expression of hematopoietic supporting genes, such as VCAM1 and CCL28. Furthermore, EGR1 overexpression markedly decreased stromal cell proliferation whereas EGR1 knoc

Error detection through mouse movement in an online adaptive learning environment

While response time and accuracy indicate overall performance, their value in uncovering cognitive processes underlying learning is limited. A promising online measure designed to track decision-making is computer mouse tracking, where mouse attraction towards different locations may reflect the consideration of alternative response options. Using a speedy arithmetic multiple-choice game in an online adaptive learning environment, we examined whether mouse movements could reflect arithmetic difficulties when error rates are low. Results showed that mouse movements towards alternative responses in correctly answered questions mapped onto the frequency of errors made in this online learning system. This mapping was stronger for the younger children, as well as for easy arithmetic problems. On an individual level, users showed more mouse movement towards their previously made response errors than towards other alternative options. This opens the possibility of adapting feedback and instruction on an individual basis through mouse tracking

Feedback-learning in 3-year-olds

Even though feedback-learning is already important from very early on, much is still unknown about the strategies young children employ when learning from feedback. Kendler’s levels of functioning theory (1979) states that there are different strategies we can employ to learn simple (i.e. one-dimensional) rules from feedback: incremental learning and hypothesis testing. Infants and young children seem to start out with slow, associative incremental learning, although direct evidence herefore is lacking. When they grow older, at least some of the four-year-old children, apply a verbal-based, hypothesis testing strategy that allows for more efficient learning (Schmittmann, van der Maas & Raijmakers, 2012). This switch in reliance seems to take place somewhere around age three or four. Importantly, during that same period, a child’s executive functions develop, possibly facilitating a switch in learning strategy. Whether and how 3-year-olds learn, and how this development is related to executive functions is still largely unknown, since rule-learning in 3-year-olds has scarcely been studied. Therefore, this study will investigate the learning strategies of 3-year-olds in simple rule-learning tasks and their relation with children’s executive function