Pyrethroid insecticides in urban salmon streams of the Pacific Northwest.

Urban streams of the Pacific Northwest provide spawning and rearing habitat for a variety of salmon species, and food availability for developing salmon could be adversely affected by pesticide residues in these waterbodies. Sediments from Oregon and Washington streams were sampled to determine if current-use pyrethroid insecticides from residential neighborhoods were reaching aquatic habitats, and if they were at concentrations acutely toxic to sensitive invertebrates. Approximately one-third of the 35 sediment samples contained measurable pyrethroids. Bifenthrin was the pyrethroid of greatest concern with regards to aquatic life toxicity, consistent with prior studies elsewhere. Toxicity to Hyalella azteca and/or Chironomus dilutus was found in two sediment samples at standard testing temperature (23 °C), and in one additional sample at a more environmentally realistic temperature (13 °C). Given the temperature dependency of pyrethroid toxicity, low temperatures typical of northwest streams can increase the potential for toxicity above that indicated by standard testing protocols.

The relations between phonological processing abilities and emerging individual differences in mathematical computation skills: a longitudinal study from second to fifth grades.

The primary purpose of this longitudinal correlational study was to examine relations between phonological processing abilities and emerging individual differences in math computation skills and also to investigate the source of covariation between reading and math computation skills in a random sample (n = 201). Phonological memory, rate of access to phonological codes in long-term memory, and phonological awareness were uniquely associated with growth in estimated total number of computation procedures mastered (general computation skills) from 92.5 to 134.8 months in age, although the contributions of the first two abilities were developmentally limited. Phonological processing almost completely accounted for the associations between reading and general computation skills. Evidence of bidirectional relations between general computation skills and simple arithmetic problem solving speed was found.

Individual solution processes while solving addition and multiplication math facts in adults.

Contrary to predictions of current solution process models, adults used a variety of procedures other than retrieval to solve addition and multiplication math facts. Predictors assumed to capture retrieval processes posited by such models did account for a substantial proportion of variance in averaged retrieval solution times. But most of the variance in individual participants' retrieval times remained unaccounted for. Cross-operation associations in patterns of strategy use and retrieval latencies were obtained. Adults with stronger higher level math achievement were more likely to use retrieval, solved math facts faster and less variably, and executed retrieval processes posited by current solution process models faster than participants with less math attainment. The results are explained within the context of the adaptive strategy choice model.

Dimensionality of posttraumatic stress disorder symptoms in children exposed to disaster: results from confirmatory factor analyses.

Factor analytic studies of trauma victims' posttraumatic stress disorder (PTSD) have offered conflicting hypotheses about how to conceptualize PTSD into symptom categories. The present study used confirmatory factor analyses of self-reported PTSD symptomatology from 5,664 child and adolescent victims of Hurricane Hugo to compare 10 models of PTSD dimensionality. PTSD was best represented by a 2nd-order PTSD factor that manifests in 3 symptom clusters (Intrusion/Active Avoidance, Numbing/Passive Avoidance, and Arousal). This model was cross-validated on 3 age groups (late childhood, early adolescence, and late adolescence), and results indicated factorial invariance across groups. PTSD symptoms varied in relative centrality to the underlying dimensions of PTSD, which differed in their relations with anxiety and degree of traumatic exposure. Implications for classification criteria and an empirically supported theory of PTSD are discussed.

Changing relations between phonological processing abilities and word-level reading as children develop from beginning to skilled readers: a 5-year longitudinal study.

Relations between phonological processing abilities and word-level reading skills were examined in a longitudinal correlational study of 216 children. Phonological processing abilities, word-level reading skills, and vocabulary were assessed annually from kindergarten through 4th grade, as the children developed from beginning to skilled readers. Individual differences in phonological awareness were related to subsequent individual differences in word-level reading for every time period examined. Individual differences in serial naming and vocabulary were related to subsequent individual differences in word-level reading initially, but these relations faded with development. Individual differences in letter-name knowledge were related to subsequent individual differences in phonological awareness and serial naming, but there were no relations between individual differences in word-level reading and any subsequent phonological processing ability.