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

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

Using a single feature to discriminate and form categories: The interaction between color, form and exemplar number

There is relatively little work that has focused on how infants use a single feature to discriminate objects or flexibly group objects together. Existing research suggests that the ease with which infants learn form and color discriminations is not equal. However, which of these dimensions is easier when discriminating between objects is still unclear. The studies in this paper tested how infants used these two dimensions under varying levels of diversity in a discrimination task. Combining traditional analyses with latent-states Markov-modeling, infant learning in these studies was characterized by a bend of overt behavior and attentional processes. Infants were able to learn both a color and form-based discrimination, but only generalized the form distinction to new stimuli. When presented with diversity on the irrelevant dimension, infants in the form condition learned quickly. However, infants in the color-condition did not show signs that they learned the distinction. The results show that infants could use both dimensions to distinguish between objects, but that form-based distinctions were easier and more likely to be generalized to new objects

What do listeners learn from exposure to a vowel distribution? An analysis of listening strategies in distributional learning

This study first confirms the previous finding that Spanish learners improve their perception of a difficult Dutch vowel contrast through listening to a frequency distribution of the vowels involved in the contrast, a technique also known as distributional training. Secondly, it is demonstrated that learners' initial use of acoustic cues influences their performance after distributional training. To that end, types of unique listening strategies, i.e., specific ways of using acoustic cues in vowel perception, are identified using latent class regression models. The results before training show a split between "low performers", who did not use the two most important cues to the Dutch vowel contrast, namely the first and second vowel formants, and "high performers", who did. Distributional training diversified the strategies and influenced the two types of listeners differently. Crucially, not only did it bootstrap the use of cues present in the training stimuli but also the use of an untrained cue, namely vowel duration. We discuss the implications of our findings for the general field of distributional learning, and compare our listening strategies to the developmental stages that have been proposed for the acquisition of second-language vowels in Spanish learners