Murray Mayberry - Academia.edu (original) (raw)

Papers by Murray Mayberry

Proceedings. Biological sciences / The Royal Society, Oct 7, 2015

Prenatal testosterone may have a powerful masculinizing effect on postnatal physical characterist... more Prenatal testosterone may have a powerful masculinizing effect on postnatal physical characteristics. However, no study has directly tested this hypothesis. Here, we report a 20-year follow-up study that measured testosterone concentrations from the umbilical cord blood of 97 male and 86 female newborns, and procured three-dimensional facial images on these participants in adulthood (range: 21-24 years). Twenty-three Euclidean and geodesic distances were measured from the facial images and an algorithm identified a set of six distances that most effectively distinguished adult males from females. From these distances, a 'gender score' was calculated for each face, indicating the degree of masculinity or femininity. Higher cord testosterone levels were associated with masculinized facial features when males and females were analysed together (n = 183; r = -0.59), as well as when males (n = 86; r = -0.55) and females (n = 97; r = -0.48) were examined separately (p-values < ...

PloS one, 2015

The Extreme Male Brain (EMB) theory posits that autistic traits are linked to excessive exposure ... more The Extreme Male Brain (EMB) theory posits that autistic traits are linked to excessive exposure to testosterone in utero. While findings from a number of studies are consistent with this theory, other studies have produced contradictory results. For example, some findings suggest that rather than being linked to hypermasculinization for males, or defeminization for females, elevated levels of autistic traits are instead linked to more androgynous physical features. The current study provided further evidence relevant to the EMB and androgony positions by comparing groups of males selected for high or low scores on the Autism-spectrum Quotient (AQ) as to the rated masculinity of their faces and voices, and comparable groups of females as to the rated femininity of their faces and voices. The voices of High-AQ males were rated as more masculine than those of Low-AQ males, while the faces of High-AQ females were rated as less feminine than those of Low-AQ females. There was no effect ...

Journal of neurodevelopmental disorders, 2015

Prenatal androgen exposure has been hypothesized to be linked to autism spectrum disorder (ASD). ... more Prenatal androgen exposure has been hypothesized to be linked to autism spectrum disorder (ASD). While previous studies have found a link between testosterone levels in amniotic fluid and autistic-like traits, a similar relationship has not been found for testosterone in umbilical cord blood. However, it may be the net biological activity of multiple androgens and estrogens that influences postnatal effects of prenatal sex steroids. Accordingly, composite levels of androgens (A) and estrogens (E) were investigated, along with their ratio, in relation to autistic-like traits in young adulthood. Sex steroid data in umbilical cord blood were available from 860 individuals at delivery. Samples were analyzed for androgens (testosterone, androstenedione, and dehydroepiandrosterone) and estrogens (estrone, estradiol, estriol, and estetrol). Levels of bioavailable testosterone, estradiol, and estrone were measured and used to calculate A and E composites and the A to E ratio. Participants w...

Frontiers in Human Neuroscience, 2013

Autism spectrum disorders (ASD) are currently diagnosed in the presence of impairments in social ... more Autism spectrum disorders (ASD) are currently diagnosed in the presence of impairments in social interaction and communication, and a restricted range of activities and interests. However, there is considerable variability in the behaviors of different individuals with an ASD diagnosis. The heterogeneity spans the entire range of IQ and language abilities, as well as other behavioral, communicative, and social functions. While any psychiatric condition is likely to incorporate a degree of heterogeneity, the variability in the nature and severity of behaviors observed in ASD is thought to exceed that of other disorders. The current paper aims to provide a model for future research into ASD subgroups. In doing so, we examined whether two proposed risk factors-low birth weight (LBW), and in utero exposure to selective serotonin reuptake inhibitors (SSRIs)-are associated with greater behavioral homogeneity. Using data from the Western Australian Autism Biological Registry, this study found that LBW and maternal SSRI use during pregnancy were associated with greater sleep disturbances and a greater number of gastrointestinal complaints in children with ASD, respectively. The findings from this "proof of principle" paper provide support for this "bottom-up" approach as a feasible method for creating homogenous groups.

Biological Psychology, 2014

Two competing theories address the influence of fetal testosterone on cerebral laterality: one pr... more Two competing theories address the influence of fetal testosterone on cerebral laterality: one proposing exposure to high fetal testosterone concentrations is related to atypical lateralisation (Geschwind-Galaburda hypothesis), the other that high fetal testosterone concentrations exaggerate typical lateralisation (callosal hypothesis). The current study examined the relationship between cord testosterone concentrations and cerebral laterality for language and spatial memory in adulthood. Male participants with high (>0.15nmol) and low (<0.10nmol) cord testosterone levels were invited to take part in the study (n=18 in each group). Cerebral laterality was measured using functional Transcranial Doppler Ultrasonography, while participants completed word generation and visual short-term memory tasks. Typical left lateralisation of language was more common in the hightestosterone group than in the low-testosterone group, χ 2 = 4.50, df = 1, p =.034. Spatial memory laterality was unrelated to cord testosterone level. Our findings indicate that fetal testosterone exposure is related to language laterality in a direction that supports the callosal hypothesis.

Early Human Development, 2015

Background Ratio of second digit length to fourth digit length (2D:4D) has been extensively used ... more Background Ratio of second digit length to fourth digit length (2D:4D) has been extensively used in human and experimental research as a marker of fetal sex steroid exposure. However, very few human studies have measured the direct relationship between fetal androgen or estrogen concentrations and digit ratio. Aims We investigated the relationships between both androgen and estrogen concentrations in umbilical cord blood and digit ratio in young adulthood. In addition we calculated measures of total serum androgen and total estrogen bioactivity and investigated their relationship to digit ratio. Study Design Prospective cohort study. Subjects An unselected subset of the Western Australian Pregnancy Cohort (Raine) study (159 female; 182 male). Outcome Measures Cord serum samples were collected immediately after delivery. Samples were assayed for androgen (testosterone, 4-androstenedione, dehydroepiandrosterone) and estrogen (estrone, estradiol, estriol, estetrol) concentrations using liquid-chromatography mass-spectrometry. Digit ratio measurements were taken from hand photocopies at age 19-22 years. Results For both males and females, there were no significant correlations between digit ratio and any androgen or estrogen concentrations considered individually, the testosterone to estradiol ratio, total androgen bioactivity measure or ratio of androgen to estrogen bioactivity (all p Umbilical Cord Sex Steroids and Digit Ratio 3 > .05). In males, but not females, total estrogen bioactivity was negatively correlated with left hand digit ratio (r =-.172, p = .02), but this relationship was no longer significant when adjusted for variables known to affect sex steroid concentrations in cord blood. Conclusions Our findings indicate that digit ratio is not related to fetal androgens or estrogens at late gestation.

Background: Increased prenatal testosterone exposure has been hypothesized as a mechanism underly... more Background: Increased prenatal testosterone exposure has been hypothesized as a mechanism underlying autism spectrum disorders (ASD). However, no studies have prospectively measured prenatal testosterone exposure and ASD. The current study sought to determine whether testosterone concentrations in umbilical cord blood are associated with a clinical diagnosis of ASD in a small number of children and with autistic-like traits in the general population. Methods: Umbilical cord blood was collected from 707 children. Samples were analyzed for total (TT) and bioavailable (BioT) testosterone concentrations. Parent report indicated that five individuals had a clinical diagnosis of ASD. Those participants without a diagnosis were approached in early adulthood to complete the Autism-Spectrum Quotient (AQ), a self-report measure of autistic-like traits, with 184 males (M = 20.10 years; SD= 0.65 years) and 190 females (M = 19.92 years; SD=0.68 years) providing data. Results: The BioT and TT concentrations of the five children diagnosed with ASD were within one standard-deviation of the sex-specific means. Spearman's rank-order coefficients revealed no significant correlations between TT levels and scores on any AQ scale among males (rho range:-.01 to .06) or females (rho value range:-.07 to .01). There was also no significant association between BioT or TT concentrations and AQ scores among males (rho value range:-.07 to .08) or females (rho value range:-.06 to .12). Males were more likely than females to have 'high' scores (upper decile) on the AQ scale relating pattern and detail processing. However, the likelihood of a high score on this scale was unrelated to BioT and TT concentrations in both males and females. Conclusions: These findings indicate that testosterone concentrations from umbilical cord blood are unrelated to autistic-like traits in the general population. However, the findings do not exclude an association between testosterone exposure in early intrauterine life and ASD.

Developmental Medicine & Child Neurology, 2014

1 Telethon Kids Institute, University of Western Australia, Perth, WA; 2 School of Psychology, Un... more 1 Telethon Kids Institute, University of Western Australia, Perth, WA; 2 School of Psychology, University of Western Australia, Perth, WA; 3 School of Women’s and Infants’ Health, University of Western Australia, Perth, WA, Australia. 4 Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Canada. 5 Department of Obstetrics and Gynaecology, University of Melbourne, Parkville, Vic., Australia.

Psychoneuroendocrinology, 2010

Prenatal exposure to testosterone has been shown to affect fetal brain maturation as well as post... more Prenatal exposure to testosterone has been shown to affect fetal brain maturation as well as postnatal cognition and behavior in animal studies. Although there are well-established sex-differences in the use of social communication (or &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;pragmatic language&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;) in humans, there has been limited investigation of the association between fetal testosterone exposure and postnatal pragmatic language ability. In this prospective study, pragmatic language skills, assessed using a pragmatic language score (PLS), were measured in 78 girls aged 10 years and correlated with testosterone levels in umbilical cord blood. A measure of the biologically active, &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;free&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; fraction of testosterone, the free androgen index (FAI), was positively correlated with the PLS (R=.3). Regression analyses showed that the FAI was a significant, positive predictor of pragmatic language difficulties in girls after controlling for maternal and infant-health variables (B=0.02, 95% confidence interval=0.01-0.04, p=0.02). This is the first prospective study to identify an association between early life testosterone exposure and pragmatic language difficulties in girls. These novel findings are discussed with reference to the &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;extreme male-brain&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39; theory of autism.

Personality and Individual Differences, 2011

ABSTRACT Difficulties binding together information in memory have often been reported in individu... more ABSTRACT Difficulties binding together information in memory have often been reported in individuals with schizophrenia, and have been linked with auditory hallucinations and the predisposition to hallucinate in particular. However, some inconsistencies remain. For example, we previously examined binding of two external sources (voice and location) in hallucination-prone individuals and found no evidence of a binding deficit using a working memory task that involved automatic binding. Consequently, the current study examined both automatic and intentional binding. The Launay-Slade Hallucination Scale-Revised (LSHS-R) was administered to 559 undergraduates from which high (25) and low (25) scorers were drawn. The binding tasks assessed either automatic or intentional binding of voice and location features. The results showed no significant differences between high and low hallucination-prone individuals in binding these two external sources of information, regardless of the type of binding (automatic or intentional) assessed. Furthermore, hallucination-prone individuals demonstrated no difficulties recognising individual features of voice identity or location. These findings suggest that some memory deficits may emerge only as psychosis fully develops.

Memory & Cognition, 1988

Set size was varied as a factor in the primary memory paradigm developed by Wickens and colleague... more Set size was varied as a factor in the primary memory paradigm developed by Wickens and colleagues <Wickens, Moody,& Dow, 1981; Wickens, Moody, & Vidulich, 1985).In Experiment 1, using adults and teenagers, no proactive interference (PI) was observed at set size 4, consistent with previous research, but PI was observed at set size 10. In Experiment 2, with adults, PI was observed at set sizes 6, 8, and 10, but not at set size 4. These results are consistent with the hypothesis that sets of more than 4 items overload primary memory, so that some items have to beretrieved from secondary memory. In Experiment 3, 8-to 9-year-olds were used with set sizes of 2 and 4. Proactive interference was observed with the larger, but not with the smaller, set. This suggests that primary memory was overloaded by 4 items at this age, indicating that its capacity increases with age. Wickens, Moody, and Dow (1981) and Wickens, Moody, and Vidulich (1985) made considerable progress toward operationalizing the distinction, originally made by William James (1890), between primary and secondary memory. As defined by James, primary memory (PM) consists of information that has not been lost to consciousness, whereas secondary memory (SM) consists of information of which we are not currently thinking. Wickens et al. (1981) ope rationalized PM and SM in the Sternberg (1975) memory scanning task. In the PM condition, a memory set is presented and followed almost immediately by the probe item, without intervening activity. In the SM condition, a distracting activity (counting backward, or a Stroop task) intervenes between memory set presentation and probe presentation, thereby removing the memory set items from consciousness. Wickens et al. (1981; Wickens et al., 1985) showed that PM and SM are distinguished by three factors in this situation: (1) information in SM has to be retrieved, whereas information in PM does not, and retrieval produces an increment in response time (RT) to the probe; (2) negative probes produce longer RTs than positive probes for SM but not for PM, probably because SM requires retrieval, and negative probes, which do not belong to the memory set, are less effective retrieval cues; and (3) proactive interference effects occur in SM but not in PM, because proactive interference is associated with retrieval. Wickens et al. (1981) used set sizes of 2 and 4 items under PM and SM conditions. Retrieval latencies were longer in the SM condition by an amount that was indepen-This work. was supported by a grant from the Australian Research Grants Scheme. We would like to thank Alan Baddeley, Delos Wickens, and three anonymous reviewers for helpful comments on an earlier draft of this paper. We also would like to thank Brett Garrigan, Susan Robinson, and Robert Lake for their careful assistance

Journal of the International Neuropsychological Society, 2004

This study examined whether a secondary verbal shadowing task influences recall for hand movement... more This study examined whether a secondary verbal shadowing task influences recall for hand movements. Descriptive verbal labels associated with hand postures (e.g., &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;fist&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;, &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;palm&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;quot;) were presented auditorily, concurrent with video presentation of hand postures, and the participant was instructed to shadow the words aloud. In the congruent verbal labels condition, the words were matched with the hand postures shown, and in the incongruent condition, the labels and hand postures were unmatched. In Experiment 1 (N = 18), a computerized version of the Kaufman Hand Movements Test (KHMT), which involves three distinct hand postures, was performed under congruent and incongruent labels conditions, and baseline. For Experiment 2 (N = 18), the same format was applied to a hand movement span task, similar to the KHMT, but based on seven distinct hand postures. For both experiments, shadowing congruent labels enhanced serial recall, whereas shadowing incongruent labels reduced recall when compared to baseline. Thus memory for hand movements was affected by the content of the secondary verbal task, consistent with participants spontaneously using a verbal recoding and rehearsal strategy to support this form of memory, a strategy enhanced through the provision of appropriate labels.

Journal of the International Neuropsychological Society, 2006

This study examined whether memory span was impaired during the acute and post-acute phases follo... more This study examined whether memory span was impaired during the acute and post-acute phases following mild traumatic brain injury (mTBI). Twenty-two adults with mTBI were compared with 22 controls on computerized tasks of immediate memory for verbal, spatial, and hand movement sequences under no interference (baseline) and articulatory suppression conditions. Groups were assessed within a month and followed up 3-12 months post-injury. In the acute phase, there were no group differences across tasks under either condition. At follow-up, all spatial and verbal span scores and associated practice effects were equivalent across groups. Yet for the hand movement task, baseline movement span was worse for the mTBI group suggesting that they failed to benefit from practice to the same extent as controls. Furthermore, the fact that this group difference in span scores disappeared when articulatory suppression was imposed indicates that successful hand movement task performance involves verbal recoding.

Journal of Memory and Language, 2009

The present study investigated the binding of verbal identity and spatial location in the retenti... more The present study investigated the binding of verbal identity and spatial location in the retention of sequences of spatially distributed acoustic stimuli. Study stimuli varying in verbal content and spatial location (e.g. V 1 S 1 , V 2 S 2 , V 3 S 3 , V 4 S 4) were followed by a recognition probe stimulus. A critical test of the binding or integration of the verbal and spatial features of the study stimuli comprised a comparison of intact probes that preserved the association of those features (e.g. V 2 S 2 or V 3 S 3) with recombined probes (e.g. V 2 S 3 or V 2 S 3) that used verbal and spatial features from study items, but in new combinations. A series of five experiments showed evidence of the binding of sound identity and location information for both verbal stimuli (spoken letters) and artificial non-verbal stimuli. While binding tended to be stronger for the more recent items of the sequence, there was consistent evidence of the retention of associations of features for the early sequence items, suggesting durability of binding of auditory features over time (at least 5.5 s) and despite the interpolated processing of other stimuli. Both spatial and verbal recognition judgments were affected by the association of verbal and spatial features when the test procedure required attention to the two classes of information. However, when participants were able to focus attention on one class of information and ignore the other, spatial recognition judgments showed an advantage for intact probes compared to recombined probes, whereas verbal recognition judgments did not. The results are discussed with reference to the primacy of identity and location in the representation of sounds in working memory.

Journal of Experimental Psychology: Learning, Memory, and Cognition, 1986

The information-processing demands of transitive inference problems were investigated with a prob... more The information-processing demands of transitive inference problems were investigated with a probe reaction-time (RT) secondary task. Two versions of a primary task were used: the standard three-term inference problem and a matched verification task that did not require premise integration. In the first two experiments the premise and target-matching components of the primary task were presented sequentially. For the transitive inference task, probe RT was especially slow when the probe occurred during the second premise phase, but no such effect was found with the matched verification task. This implies that premise integration imposed an increased load on processing resources. A third experiment showed that the processing demand associated with premise integration also occurred with simultaneous presentation. Other variations in problem form (e.g., premise markedness, negation, and pivot search) did not influence probe RT, although they are known to affect solution time. Thus, solution time and measures of processing load may be independent. The first experiment was supported by a grant from the Australian Research Grants Scheme. The second and third experiments form part of the PhD project conducted by the first author. We thank Mike Bibo for excellent work on the first experiment and also Gordon Logan, Colin MacLeod, Robert Sternberg, and an anonymous reviewer for helpful comments on earlier drafts.

Journal of Clinical and Experimental Neuropsychology, 2005

A meta-analysis conducted by Binder, Rohling and Larrabee established a relationship between mild... more A meta-analysis conducted by Binder, Rohling and Larrabee established a relationship between mild traumatic brain injury (TBI) and small reductions in cognitive functioning in individuals assessed more than 3 months post-injury. As a follow-up, this study summarized similar research that (1) was published since the previous meta-analysis, and (2) included data collected at any stage post-injury. An extensive literature search revealed 17 suitable studies from which effect sizes were aggregated. The overall effect size was g = 0.32, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .001. Speed of processing measures had the largest effect, g = 0.47, p &amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;lt; .001. The merging of post-acute effect sizes with those reported in Binder et al.&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;s review yielded a nonsignificant result, g = 0.11. Time since injury was found to be a significant moderator variable, with effect sizes tending to zero with increasing time post injury.

Journal of Child Psychology and Psychiatry, 2012

Background: Preliminary evidence suggests that prenatal testosterone exposure may be associated ... more Background: Preliminary evidence suggests that prenatal testosterone exposure may be associated with language delay. However, no study has examined a large sample of children at multiple time‐points.Methods: Umbilical cord blood samples were obtained at 861 births and analysed for bioavailable testosterone (BioT) concentrations. When participating offspring were 1, 2 and 3 years of age, parents of 767 children (males = 395; females = 372) completed the Infant Monitoring Questionnaire (IMQ), which measures Communication, Gross Motor, Fine Motor, Adaptive and Personal–Social development. Cut‐off scores are available for each scale at each age to identify children with ‘clinically significant’ developmental delays. Chi‐square analyses and generalized estimating equations examined longitudinal associations between sex‐specific quartiles of BioT concentrations and the rate of developmental delay.Results: Significantly more males than females had language delay (Communication scale) at...

The Quarterly journal of experimental psychology. A, Human experimental psychology, 2002

The nature of the mechanisms that code item position in serial short-term verbal recall was inves... more The nature of the mechanisms that code item position in serial short-term verbal recall was investigated with reference to temporal grouping phenomena--effects that arise when additional pauses are inserted in a presented list to form groups of items. Several recent models attempt to explain these phenomena by assuming that positional information is retained by associating items with contextual information. According to two of the models--the Phonological Loop model (Hitch, Burgess, Towse, & Culpin, 1996) and the OSCAR model (Brown, Preece, & Hulme, 2000)--contextual information depends critically on the timing of item presentation with reference to group onset. By contrast, according to the Start-End model (Henson, 1998) and a development from it, which we label the Oscillator-Revised Start-End model (Henson & Burgess, 1997), contextual information is independent of time from group onset. Three experiments examined whether coding of position is time dependent. The critical manipula...

Journal of experimental psychology. Learning, memory, and cognition, 2005

According to several current models of short-term memory, items are retained in order by associat... more According to several current models of short-term memory, items are retained in order by associating them with positional codes. The models differ as to whether temporal oscillators provide those codes. The authors examined errors in recall of sequences comprising 2 groups of 4 consonants. A critical manipulation was the precise timing of items within the groups, whereby temporal position (time from group onset) and ordinal position (number of items from group onset) were partially unconfounded. Errors that involve items migrating across groups should preserve within-group temporal position according to oscillator models, but should preserve within-group ordinal position according to nonoscillator models. Results from the intergroup errors strongly favored preservation of ordinal rather than temporal position.

Developmental Medicine & Child Neurology, 2010

Aim Fetal androgens influence fetal growth as well as postnatal neurocognitive ability. However,... more Aim Fetal androgens influence fetal growth as well as postnatal neurocognitive ability. However, to our knowledge, no published study has prospectively examined the impact of early‐life androgens on infant brain growth. We report the association between circulating fetal androgen levels, measured from umbilical‐cord blood at birth, and a proxy measure of brain growth: head circumference.Method Participants were 82 unselected female infants from a large representative birth cohort (mean gestational age 39.4wks, SD 1.7). Umbilical‐cord blood was obtained at birth and analysed for androgen concentrations (total testosterone, androstenedione, dehyrdroepiandrosterone, and its sulphated metabolite). Head circumference and two other measures of growth – weight (mean 3311.4g, SD 461.3) and length – were measured within 3 days of birth and again at approximately 1 year of age (mean age 13.1mo, SD 1.1).Results Multivariate linear regressions found an inverse association between levels of f...