The associations between social support and depression, and between stress and depression have been the subject of considerable research, and although this has included longitudinal designs, these have rarely controlled for genetic effects that mediate these associations. The sample comprised 7,356 female and 4,882 male participants aged 18-95 from the Australian NHMRC Twin Registry (ATR). Of these, between 100 and 324 female pairs and between 41 and 169 male pairs, depending on the measure, were monozygotic (MZ) pairs discordant for depression. We use the co-twin control design in combination with prospective analyses to explore the association between a composite of predictors (perceived social support, stress, and support × stress) and depression. With familial effects included, both perceived support and stress were antecedents to, and sequelae of, depression, but no stress-buffering occurred. With familial effects controlled, stress was a sequela of a prior depressive episode, and neither lack of support nor stress were antecedents to depression, though their interaction approached significance for males. The male twin who later became depressed had previously reported lower perceived support in the face of multiple stressors compared to his co-twin who did not become depressed. We show that associations commonly observed with prospective designs are partly due to familial factors.

Since the late 1980s, Australian forecasters have used the seasonal climate forecast (SCF) statement 'In the next three months, the probability of getting above median rainfall is 30%.' Study one (n=63) established a baseline of whether laypersons interpreted this statement as forecasting wetter or drier conditions than normal. Although the statement is forecasting a greater likelihood of drier conditions than normal, 76% incorrectly interpreted the statement as forecasting a wetter season than normal. Using testing conditions identical to study one, in study two (n = 71), to improve accuracy, we inserted the word only in the statement (i.e. ' ...probability of getting above median rainfall is only 30%'). While the probability itself had not changed, a drop to just 24% errors suggested participants were ambiguous about how to interpret this probability. A body of research by Gigerenzer and others shows peoples' ability to reason with probabilities is enhanced by frequency probabilities rather than single-event probabilities. Study three (n =51) used the frequency (i.e. 3 in 10) rather than single-event (i.e. 30%) format tested in studies one and two. Only 22% made errors showing participants better understood how to interpret the frequency probability. We discuss formats for presenting the SCF and argue the frequency format more effectively conveys the chance nature of forecasts.

The genetic factor structure of a range of learning measures was explored in twin children, recruited in preschool and followed to Grade 2 (N = 2,084). Measures of orthographic learning and word reading were included in the analyses to determine how these patterned with the learning processes. An exploratory factor analysis of the genetic correlations among the variables indicated a three-factor model. Vocabulary tests loaded on the first factor, the Grade 2 measures of word reading and orthographic learning, plus preschool letter knowledge, loaded on the second, and the third was characterized by tests of verbal short-term memory. The three genetic factors correlated, with the second (print) factor showing the most specificity. We conclude that genetically influenced learning processes underlying print-speech integration, foreshadowed by preschool letter knowledge, have a degree of independence from genetic factors affecting spoken language. We also argue that the psychology and genetics of associative learning be afforded a more central place in studies of reading (dis)ability and suggest some links to molecular studies of the genetics of learning.

The genetic and environmental overlap between static and dynamic measures of preschool phonological awareness (PA) and their relation to preschool letter knowledge (LK) and kindergarten reading were examined using monozygotic and dizygotic twin children (maximum N = 1,988). The static tests were those typically used to assess a child’s current level of PA such as blending and elision, and the dynamic test included instruction in phoneme identity to assess the child’s ability to respond to this instruction. Both forms were influenced by genes and by shared and nonshared environment. The static and dynamic versions were influenced by the same genes, and part of the total genetic influence was shared with LK. They were subject to both overlapping and independent shared environment influences, with the component in common also affecting LK. Nonshared environment influences were mostly independent. Scores from dynamic assessment added only minimally to variance explained in kindergarten reading after LK and static assessment had been factored in. Although one of the genetic factors that influenced both forms of PA also affected kindergarten reading, it was only the one shared with LK. The authors conclude that dynamic assessment of PA in preschool offers little advantage over the more commonly used static forms, especially if LK scores are available, although they acknowledge its potential in cases of preschool educational disadvantage.

Genetic and environmental relations between vocabulary and reading skills were explored longitudinally from preschool through Grades 2 and 4. At preschool there were strong shared-environment and weak genetic influences on both vocabulary and print knowledge but substantial differences in their source. Separation of etiology for vocabulary and reading continued for word recognition and decoding through Grade 4, but genetic and environmental correlations between vocabulary and reading comprehension approached unity by Grade 4, when vocabulary and word recognition accounted for all of the genetic and shared environment influences on reading comprehension.

We explored errors interpreting the seasonal climate forecast (SCF) statement "In the next 3 months, the probability of exceeding median rainfall is 30%" used by the Australian media. Study one comprised 73 farmers and 12 climate staff and (1) developed a five-item multiple-choice questionnaire assessing understanding for the SCF, and (2) assessed errors interpreting the statement. The farmers who incorrectly interpreted the statement (29%) as forecasting a wetter season than normal had a lower understanding of the statement, in contrast to farmers making the correct interpretation (56%) and the climate staff. The statement appeared to be misinterpreted as a specific value of rain that was above the median by 30%, because of (1) difficulty conceptualizing 'above median rainfall' and 'below median rainfall' as distinct events, and (2) the percentage being interpreted as a specific value and not as a notion of chance. Study two, with 72 laypersons, showed more errors and slower responses with statements of probabilities less than 50% (i.e. 30%) than statements of probabilities greater than 50% (i.e. 70%), explained by the positive connotation biases of the event 'above median rainfall' and/or the use of the term 'probability'.

We present one of the first behavior-genetic studies of individual differences in school students' levels of achievement in instructed second language acquisition (ISLA). We assessed these language abilities in Australian twin pairs (maximum N pairs = 251) by means of teacher ratings, class rankings, and self-ratings of proficiency, and used the classic twin design to estimate the relative influences of genes, shared (family/school) environment, and unique environment. Achievement in ISLA was more influenced by additive genetic effects (72%, 68%, and 38% for teacher ratings, class rankings, and twin self-ratings, respectively) than by shared environment effects, which were generally not substantial (20%, 07%, and 13%). Genetic effects distinct to speaking and listening, on the one hand, and reading and writing, on the other, were evident for the twin self-ratings. We discuss the limitations and implications of these findings and point to research questions that could profitably be addressed in future studies.