The Structure of Working Memory From 4 to 15 Years of Age.

The structure of working memory and its development across the childhood years were investigated in children 4-15 years of age. The children were given multiple assessments of each component of the A. D. Baddeley and G. Hitch (1974) working memory model. Broadly similar linear functions characterized performance on all measures as a function of age. From 6 years onward, a model consisting of 3 distinct but correlated factors corresponding to the working memory model provided a good fit to the data. The results indicate that the basic modular structure of working memory is present from 6 years of age and possibly earlier, with each component undergoing sizable expansion in functional capacity throughout the early and middle school years to adolescence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Scanning probe microscopy of intrafibrillar crystallites in calcified collagen

Vertebrate mineralized tissues are composite materials formed by the organized growth of carbonated apatite crystals within a matrix of collagen fibres. Calcified collagen from turkey tendon was investigated using scanning tunnelling microscopy (STM) and atomic force microscopy (AFM). Samples were treated with hydrogen peroxide to enhance the mineralized phase by removing part of the collagen matrix and the results compared with the untreated material. Plate-like crystalline entities with dimensions 35 nm × 5–8 nm by 1.5 nm were seen. These dimensions are consistent with previous reports using transmission electron microscopy (TEM) of calcified tendon and topographic imaging of tendon crystals. The resolution of the images obtained using STM is better than the previously reported pictures obtained using TEM or scanning electron microscopy (SEM). The value of 35 nm is the same as the gap region in the structure of the collagen fibrils. Stacking of plates and plate-aggregates are a dominant feature in the scanning images. These results support the concept of organized intra-fibril mineral crystals within the organic collagen matrix. Electron diffraction and X-ray diffraction were undertaken on the samples and the patterns recorded match those previously reported for carbonated apatite.     

Phonotactic influences on short-term memory

The impact of phonotactic probabilities on serial recall was investigated in a series of experiments. In Experiments 1A and 1B, 7 and 8 year olds were tested on their serial recall of monosyllabic words and of nonwords varying in phonotactic frequencies. A recall advantage to words over nonwords remained when stimuli were balanced for phonotactic probability, but nonword recall showed superior accuracy for high over low probability nonwords, as in Experiment 2. The nonword frequency effect appears to reflect the frequency of constituent syllables rather than biphones. Both lexicality and high phonotactic frequency led to increased proportions of full over partial recall of the memory stimuli. These findings indicate that decayed memory traces in phonological short-term memory can be reconstructed using either lexical or phonotactic knowledge.     

Phonological short-term memory and new word learning in children.

Sixty-five 5-year old children participated in 4 experimental tasks of word learning that varied systematically in the amounts of phonological and nonphonological learning required. Measures of the children's performances on 2 measures of phonological memory (digit span and nonword repetition), vocabulary knowledge, and nonverbal ability were also obtained. Learning of the sound structures of new words was significantly, and to some degree independently, associated with aspects of both phonological memory skill and vocabulary knowledge. Learning of pairs of familiar words was linked with current vocabulary knowledge, although not with phonological memory scores. The findings suggest that both existing lexical knowledge and phonological short-term memory play significant roles in the long-term learning of the sounds of new words. The study also provides evidence of both shared and distinct processes contributing to nonword repetition and digit span tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neuropsychology and working memory: A review.

Reviews the relationship between neuropsychological approaches to human memory and the working memory theory introduced by A. D. Baddeley and G. J. Hitch (1974). It is argued that neuropsychological perspectives have made a number of different contributions to the development of the theory. On occasion, they have provided unique natural experiments that cannot be simulated in the laboratory and that represent a significant input to theoretical refinement. They also yield a rich source of information on a central tenet of working memory theory, which is that the components of working memory support everyday complex cognitive activities. Neuropsychological studies have played an important role in identifying the contributions of the phonological loop to the acquisition and processing of language and of the visuospatial sketchpad to learning to recognize new faces. More generally, neuropsychological investigations have substantially reinforced developments of theory based on work from the experimental laboratory, and they provide convincing evidence for the robustness and generality of the theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Life prediction for fatigue of T800/5245 carbob-fibre composites: II. Variable-amplitude loading

This is the second of two papers describing the fatigue response of a [(±45,0₂)₂]_s laminate of the T800/5245 composite system, a modern aerospace material consisting of high-failure-strain, intermediate-modulus carbon fibres in a toughened bismaleimide resin system. In the first paper, the fatigue response in repeated tension, repeated compression, and mixed tension-compression was determined at constant stress levels over a wide range of R values. The results of those constant-amplitude experiments were then used to define a programme of four- and two-block variable-loading experiments in an attempt to derive predictive methods for such loading conditions. Formulae have been developed to predict life under non-linear cumulative damage conditions and empirical data derived to validate the procedures.     

Assessment of working memory in six- and seven-year-old children.

Using cognitive methods to fractionate functionally distinct aspects of short-term memory, a test battery was designed to tap the A. D. Baddeley and G. Hitch (1974) model of working memory. The battery was administered to 87 children aged 6 and 7 years; other standardized attainment measures were obtained for a subgroup of the children concurrently and 1 year later. Correlations between subtest scores indicated high construct validity for the central executive and phonological loop measures, although not for the visuospatial measures. Central executive scores shared unique associations with performance on the vocabulary, literacy, and arithmetic tests, whereas phonological loop scores shared specific associations with vocabulary knowledge only. The substantial internal and external validity of the test battery establishes its suitability for guiding detailed theoretical analyses of working memory function. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Phonological working memory in very young children.

This study was designed to establish whether phonological working memory skills could be assessed in children below 4 yrs of age. A group of 2- and 3-yr-old children were tested on 3 phonological memory measures (digit span, nonword repetition, and word repetition) and were also given tasks that tapped other cognitive skills. Scores on the 3 phonological memory tasks were closely related. In addition, repetition performance was linked with both vocabulary knowledge and articulation rate. Results indicate that phonological memory skills can be reliably assessed in very young children by using conventional serial span and repetition procedures. (PsycINFO Database Record (c) 2010 APA, all rights reserved)