Cluster-ion bombardment studies to reveal the amorphization mode in strained Si0.8Ge0.2

Radiation damage caused by cluster ions of different sizes is predicted to be distinctly different if materials follow disparate phenomenological models of amorphization, namely overlap and direct amorphization methods. Determination of an amorphization model for a crystalline solid can be accomplished based on its radiation response to cluster sizes of bombarding ions. In the present study, we use this approach and apply it to study radiation damage in Si_0.8Ge_0.2 caused by Ag _n clusters with the number of atoms in a cluster, n, taking values from 1 to 4. The displacements measured by using channeling Rutherford backscattering spectrometry show size-enhanced damage accumulation, which is in good agreement with the atomistic detail obtained by molecular dynamics simulations. Our studies suggest that strained SiGe, a material known to have poor radiation tolerance, follows the overlap model rather than the direct amorphization model.     

Diminished testing benefits in young adults with attention-deficit hyperactivity disorder

Memory retrieval has been shown to enhance the long-term retention of tested material; however, recent research suggests that limiting attention during retrieval can decrease the benefits of testing memory. The present study examined whether testing benefits are reduced in young adults with attention-deficit hyperactivity disorder (ADHD). College students with and without ADHD read three short prose passages, each followed by a free recall test, a restudy period or a distractor task. Two days later participants recalled the passages. Although participants without ADHD did not show a significant benefit of testing over restudying, testing did produce recall benefits relative to not taking a test. These testing benefits were diminished in participants with ADHD, who did not show any advantage of testing over either restudying or no test. The absence of testing benefits in the ADHD group is likely due in part to decreased recall on the initial test. These findings have implications for improving educational practices among individuals with ADHD and also speak to the need to examine individual differences in the effectiveness of testing as a learning strategy.     

Concreteness effects revisited: The influence of dynamic visual noise on memory for concrete and abstract words

Two experiments are presented that investigate the effects of dynamic visual noise (DVN) on memory for concrete and abstract words. Memory for concrete words is typically superior to that of abstract words and is referred to as the concreteness effect. DVN is a procedure that has been demonstrated to interfere selectively with visual working memory and the generation of images from long-term memory. It was reasoned that if concreteness effects arise because of the ability of the latter to activate visual representations, then DVN should selectively impair memory for concrete words. Experiment 1 found DVN to selectively reduce free recall of concrete words. Experiment 2 investigated recognition memory and found DVN to reduce memory accuracy and remember responses, while increasing know responses to concrete words.     

The costs and benefits of testing text materials

Tests have been shown to improve the later recall of tested information, a result known as the testing effect. Tests, however, can also impair the later recall of related information, an effect known as retrieval-induced forgetting. Although retrieval-induced forgetting has been demonstrated using a wide variety of materials, recent work suggests that learning information in the context of a coherent text passage may afford protection from retrieval-induced forgetting. In four experiments we explored the conditions under which retrieval-induced forgetting does and does not occur with such materials. We found that two factors—the coherence of the to-be-learned material and the competitiveness of retrieval practice—are important in determining whether retrieval-induced forgetting does or does not occur. Furthermore, even if retrieval-induced forgetting does occur, having the opportunity to restudy the forgotten information can prevent that forgetting from persisting. Taken together, these findings provide greater understanding of the costs and benefits of testing text materials, with possible implications for the optimisation of testing as a tool for learning in educational contexts.     

Serial-position effects for items and relations in short-term memory

Two experiments used immediate probed recall of words to investigate serial-position effects. Item memory was tested through probing with a semantic category. Relation memory was tested through probing with the word's spatial location of presentation. Input order and output order were deconfounded by presenting and probing items in different orders. Primacy and recency effects over input position were found for both item memory and relation memory. Both item and relation memory declined over output position. The finding of a U-shaped input position function for item memory rules out an explanation purely in terms of positional confusions (e.g., edge effects). Either these serial-position effects arise from variations in the intrinsic memory strength of the items, or they arise from variations in the strength of item–position bindings, together with retrieval by scanning.     

Object specificity and personal relevance in long-term visual remembering

The personal relevance of an object is multi-faceted, each facet being capable of contributing to the effects on object memory attributed to personal relevance. An object's status as an individual object (object specificity), rather than just a category of object, is one such facet and its impact on the long-term visual remembering of everyday objects is assessed in two experiments. Images and drawings were produced under generic (e.g., “Please draw a bed”) and personal exemplar (e.g., “Please draw your bed”) instructions, and participants indicated the degree to which the image on which their drawing was based was of a specific object or a generic object. Object specificity induced a sense of time and place for a remembered object, the most recent encounter with the object being most salient. Other aspects of personal relevance collectively facilitated the retrieval of an object's category-irrelevant features (thereby increasing the vividness of the object image), the other objects with which it was seen, and a more general episodic sense of place. Against a broader theoretical perspective, it is proposed that visual episodic memory and visual knowledge are primary sources of information for specific personally relevant objects and generic objects, respectively.     

Dual processes,evolution and rationality

In three experiments we tested hypotheses derived from the goal specificity literature using a real-world physics task. In the balance-scale paradigm participants predict the state of the apparatus based on a configuration of weights at various distances from the fulcrum. Non-specific goals (NSG) have been shown to encourage hypothesis testing, which facilitates rule discovery, whereas specific goals (SG) do not. We showed that this goal specificity effect depends on task difficulty. The NSG strategy led to rule induction among some participants. Among non-discoverers, SG participants were faster and more accurate on difficult problems than NSG participants. The use of misleading exemplars (scale configurations that obscured the rule governing outcomes) led to fixation on inappropriate hypotheses for NSG but not SG participants. When more diagnostic learning exemplars were used, NSG non-discoverers still performed worse than SG participants on difficult problems. SG participants also outperformed NSG participants on a post-test of difficult problems. These findings qualify the generality of goal specificity effects.     

Redundancy effects in the perception and memory of visual objects

Is visual representation of an object affected by whether surrounding objects are identical to it, different from it, or absent? To address this question, we tested perceptual priming, visual short-term, and long-term memory for objects presented in isolation or with other objects. Experiment 1 used a priming procedure, where the prime display contained a single face, four identical faces, or four different faces. Subjects identified the gender of a subsequent probe face that either matched or mismatched with one of the prime faces. Priming was stronger when the prime was four identical faces than when it was a single face or four different faces. Experiments 2 and 3 asked subjects to encode four different objects presented on four displays. Holding memory load constant, visual memory was better when each of the four displays contained four duplicates of a single object, than when each display contained a single object. These results suggest that an object's perceptual and memory representations are enhanced when presented with identical objects, revealing redundancy effects in visual processing.     

Attentional attraction of receptive fields can explain spatial and temporal effects of attention

A multitude of attentional effects were found at both the neural and behavioural levels of perception; however, the nature of the attentional mechanism is an unsettled issue. It is typically assumed that the fundamental impact of attention is enhancement of neuronal responses, but some attentional effects are difficult to explain by such gain modulations. Here we offer a different view: We suggest that the most fundamental impact of attention is the attraction (shift) of receptive fields towards the attended location. We further show, both conceptually and by model simulations, that this attraction of receptive fields can explain a diverse range of attentional effects, spatial as well as temporal, linking physiological measurements at the unit level with psychophysical observations (e.g., enhanced contrast sensitivity, enhanced spatial resolution, the Mexican-hat profile of attention, prolonged perceived duration, prior entry, degraded temporal resolution).     

Parent-Child Psychotherapy: A Follow-Up Study Comparing Two Techniques

The “lost letter technique” was validated against actual election returns in two randomly selected precincts in Greensboro, North Carolina. The technique was not successful in predicting the outcome of the presidential race. It was found that letters addressed to The Health Research Center were significantly more likely to be returned than letters addressed to presidential candidates. This indicated that the failure to predict was due either to voter apathy in this particular election or to an active dislike of both candidates.