Functional Neurological Disorder (FND) is a condition that encompasses a wide spectrum of neurological symptoms that do not have an organic explanation. It is not clear why some patients develop a specific neurological symptom. In our study we considered the most frequent FND sub-types: functional motor disorders (FMD) and non-epileptic seizures (NES). It has been purported that individuals with risk factors, create strong expectations about body sensations based on clinical experiences such as disease, injury or surgery. These expectations would impact the nervous system which in turn lead to functional symptoms. These symptoms are inconsistent in frequency and evolution across time, and they are vulnerable to suggestion. Thus, there are no objective measures that can account for the symptoms. This thesis aims to determine whether previous clinical factors affecting different parts of the body have a relationship with the development of functional motor disorder (FMD) and non-epileptic seizures (NES), and to carry out a preliminary study of a measure capable of identifying perceptual differences in patients with functional weakness, the most reported symptom. In the first study we analysed the medical records of 108 FND patients (52 FMD and 56 NES), and in the second study we applied the Size-Weight Illusion (SWI) to 11 FND patients with functional weakness and 15 healthy controls (HC). It was found that patients with motor symptoms (FMD) had significantly higher rates of clinical factors that affected their limbs prior to the symptom onset than NES. Moreover, contrary to predicted, patients with NES had a similar rate of events that affected their head than FMD. However, NES had a higher rate of clinical factors during their lifetime than FMD, such as dissociative symptoms, suicidal ideation, and being victim of bullying, which affect the mind, and from the patients’ perspective they can be considered as located in the head. In the second study, FND and HC experienced a similar size-weight illusion. The severity and laterality of the symptom did not impact on the strength of the illusion, nor the dominance of the affected side. However, we propose that it is likely to find an effect in FND with a larger sample size. Otherwise, if similar results were found in future studies, the SWI might be a test that provides an objective assessment to confirm FND has a normal perception of weight relative to size.

It has been recently claimed that measures of spontaneous electroencephalography (EEG) signal complexity, such as Lempel-Ziv Complexity (LZc), can provide an index of an individual’s level of consciousness. Research and clinical practice are currently limited to unreliable behavioural and physiological measures to indicate consciousness. Therefore, there is significant urgency for an objective, reliable, brain-based measure of consciousness. EEG complexity measures utilise algorithms from Information Theory to quantify the diversity in spontaneous EEG data. These are being used to measure the diverse neural activity which necessarily underlies conscious experience. LZc assesses the complexity of multi-channel EEG data using a compression algorithm. Studies of LZc typically involve comparing conditions of altered consciousness with periods of conscious wakefulness. These studies suggest that the change in complexity observed is reflective of the change in level of consciousness. However, very little is known about how LZc varies, either with or without a corresponding change in consciousness. The present study utilised portable long-wear EEG to record multi-day, continuous EEG data from two participants (a total of 8 days for Participant 1 and 4 days for Participant 2). Data from each participant was analysed independently. A LZc algorithm was used to compute a complexity value for every non-overlapping 10-second segment. Results demonstrated that, as with previous research, LZc during Wake (14-hours during the day, multiple days per participant) is, on average, higher than during sleep (Stage N1, Stage N2, Slow-Wave-Sleep, and REM sleep). However, there is considerable variation surrounding these means. Visualising LZc across Wake revealed a consistent but wide spread of variability around the mean, with a scattering of low LZc values reflected by a negative skew in the data. This also results in a wide range of possible mean LZc values made available from taking samples (between 1 and 120 minutes in duration) during this period. Although this variability reduces with larger samples sizes, even day-to-day, LZc can significantly differ within a person. Regardless of the source of this variability, its presence causes concern due to the overarching clinical motivations and potential practical applications of this measure. These results suggest that LZc may not be indicative of level of consciousness, as previously claimed. The issues raised and addressed in this study are not unique to LZc, but will apply to all complexity algorithms, current and future. With this study, we have shown that long-duration EEG is a successful framework for identifying variability in a complexity measure of consciousness. This information-rich dataset is uniquely capable of exposing and investigating complexity measures, with the additional insight of observing and analysing complexity across time. This study endeavours to redirect discussions of this field and promote the use of this framework to both acknowledge and empirically address all surrounding issues and assumptions. All complexity measures should undergo reliability testing as both a proof of concept and a proof of practice before being utilised in research or clinical applications.

During the key periods of adolescence and emerging adulthood, individuals can be particularly vulnerable to experiencing suboptimal wellbeing and functioning. With potential long-term impacts on adult trajectories, early wellbeing promotion is critical. This study aimed to further understand wellbeing development across adolescence and into emerging adulthood, by examining the role of a range of individual and environmental characteristics. The individual characteristics examined included temperament, anxiety symptoms, and depression symptoms. Environmental characteristics included parental responses to emotion expression, parental mental health, stressful life events, and maltreatment. The role of emotion regulation strategies were also explored in relation to the characteristics and wellbeing. The study utilised a longitudinal community cohort from the Adolescent Development Study, recruited from schools across Melbourne, Australia. The sample included 245 families who completed questionnaires across three time points. At time 1 (mean age = 12.45), measures of temperament, depression symptoms, anxiety symptoms, parental depression symptoms, parental anxiety symptoms, and parental responses to offspring emotion expression were completed. At time 2 (mean age = 15.01), adolescents completed measures of stressful life events and maltreatment. They completed emotion regulation and wellbeing measures at the final time point (mean age = 18.83). Predictor variables were factor analysed within each domain in order to provide sufficient representation of the structure of the data. A series of path analyses, controlling for gender and SES revealed that temperament traits, neglect, and abuse predicted wellbeing and functioning outcomes. Bootstrap path analyses (using 95% confidence intervals for the indirect effect) revealed significant associations between the emotion regulation strategies of rumination, distraction, mindfulness, cognitive reappraisal, and expressive suppression with the individual and environmental characteristics, and wellbeing and functioning outcomes. Findings suggest that wellbeing development across adolescence and emerging adulthood is associated with individual characteristics (e.g., temperament), as well as environmental experiences that deviate from adaptive ranges (e.g., neglect). The various patterns found in the study reinforce the salience of examining wellbeing as a multifaceted construct, with aspects of wellbeing potentially having different developmental pathways. Furthermore, emotion regulation strategies may be important for wellbeing pathways, with maladaptive strategies (e.g., rumination) being associated with lower wellbeing and adaptive strategies (e.g. mindfulness) associated with higher wellbeing. Therefore, emotion regulation may be a suitable target for optimising youth wellbeing.

Autism Spectrum Disorder (ASD) is a complex neurodevelopmental condition characterised by impairments in two core domains of social communication deficits and restricted, repetitive behaviours or interests. A milder variant of autism-like characteristics, known as the Broader Autism Phenotype (BAP), is present at higher rates in relatives of individuals with ASD than the general population, indicating a genetic liability for ASD. There is a wealth of social cognitive research documenting theory of mind, empathising, and emotional face processing deficits in ASD and the BAP, which correspond to abnormal brain function in the “social brain”. However, less research has been conducted on the brain and behavioural correlates of emotional voice processing in ASD and the BAP, despite its significance for social cognition. This thesis aimed to profile emotional voice processing abilities in ASD and the BAP in relatives and the general population, specifically relating to non-linguistic vocalisations known as vocal affect bursts (e.g., laughter, cries, screams). This thesis also aimed to identify the neurobiological substrates of emotional voice processing in individuals with ASD and relatives with the BAP. Three studies were performed to address these aims, each using the same purpose-built, web-based and/or functional MRI (fMRI) task to assess behavioural performance and elicit brain activation. Whole-brain activation elicited by the fMRI task was assessed using random- and fixed-effects analyses (RFX and FFX), which allowed inferences to be made on the population and sample levels, respectively. Study 1 examined vocal affect burst recognition and its neurobiological correlates in individuals with high-functioning ASD (n = 16) compared to typically-developing controls (n = 16). The ASD group demonstrated a vocal emotion recognition deficit on the web-based task, where they misclassified neutral non-linguistic voices as expressing basic emotions at a higher rate than controls. RFX analyses revealed no significant group differences in brain activation, whereas FFX analyses revealed that the ASD group demonstrated higher activation relative to controls in widely distributed regions associated with emotional voice processing, executive function, memory, motor and somatosensory processing, and visual processing. These findings enable atypical brain activation to be inferred for this specific ASD cohort, but not for the wider ASD population. Although cohort-specific, such information may facilitate hypothesis generation for future investigations of neurobiological compensation in ASD. Study 2 addressed the same research questions as Study 1 in relatives of individuals with ASD (n = 13) who were determined to have the BAP on clinical assessment. The BAP group demonstrated no vocal emotion recognition deficit relative to controls (n = 13) on the web-based task. Under FFX analyses alone (not RFX analyses), the BAP group demonstrated significantly higher activation in the left lateral occipital cortex relative to controls. Inferences about the FFX findings are limited to the specific BAP cohort assessed here, and cannot be extended to the wider population of ASD-relatives with the BAP. Nonetheless, these findings may inform new hypotheses exploring endophenotypes (i.e., intermediate phenotypes) of ASD, characterised by a similar expression of neurobiological compensation in ASD and the BAP. Study 3 used the web-based task to assess the association between vocal affect burst recognition and the continuous distribution of BAP traits in the general population of individuals without a family history of ASD. It was hypothesised that lower recognition accuracy for the six basic emotions would correlate with higher self-ratings of BAP traits. In contrast to expectations, higher classification accuracy (and emotional intensity ratings) for angry voices correlated significantly with higher self-ratings of rigid BAP traits. The specific anger-rigid association indicates that enhanced auditory threat detection constitutes an aspect of the BAP in the general population. Further research is recommended to examine whether this relationship is mediated by underlying personality factors like neuroticism or trait anxiety. Overall, different behavioural profiles of emotional voice processing abilities were observed in individuals with ASD (deficit—misclassifying neutral voices as being emotional), relatives with the BAP (no deficit—intact performance), and individuals from the general population with higher levels of BAP traits (advantage—enhanced sensitivity to angry voices). The neuroimaging findings of enhanced activation in the specific ASD and BAP cohorts assessed here may have implications for future research investigating the role of neurobiological compensation for emotional voice processing in their respective populations, potentially including the exploration of endophenotypes of ASD. Such studies would ideally include larger ASD and BAP (relatives) samples that enable the assessment of more homogenous, identifiable subgroups who may be susceptible to increased cognitive demands for emotional voice processing. This thesis extends research on social cognition within the voice modality in ASD and the BAP, and may have wider implications for understanding the genetic aetiology of social communication impairments in ASD.

Many theories of number propose that humans possess a ‘mental number line’ (MNL) representation. The MNL is commonly measured with a number-to-position (NP) task, and this task is often used to make inferences about the MNL representation. However, most research on MNL representations to date has made assumptions about the properties of the MNL without considering the role of ordinal relationships between numbers. The research reported in this thesis examined whether the MNL metaphor should be extended to include ordinal relationships, and to examine the nature of these relationships. A pilot study tested whether a linear MNL representation could be shifted with logarithmic training. Adults completed a series of logarithmic feedback sessions, and their NP task performance was assessed at the end of each training block. Findings revealed little to no systematic effect of logarithmic training on NP task performance, despite participants successfully learning the logarithmic function. They also revealed individual differences in the overall impact and learning of the logarithmic feedback. These findings suggested that relationships between numbers may change to allow accurate task performance, which may not be reflected in the NP task. Study 1 tested whether the linear response profile that describes NP performance is specific to number, or whether this pattern of responding is a feature of ordered lists more generally. Adults were given NP and alphabet-to-position tasks. Findings showed that numbers and letters both displayed similar linear trends. This suggested that the linear profiles attributed to number may reflect the way in which ordinal lists of symbols are learned. Studies 2a and 2b investigated whether leaning a list of novel symbols is mediated by the underlying spatial properties of the symbols (e.g., spatial complexity). Novel symbols were used to minimise the overlearned nature of Hindu-Arabic numerals. Study 2a aimed to determine the ideal novel symbol set to use in Study 2b, specifically, one which could be ordered by complexity. Participants made judgements on two novel symbol sets, and their relationship to a range of numerical stimuli. In Study 2b, a paired comparisons training method was used to teach participants the order of a list of novel symbols. Participants were allocated to either a spatial complexity or a random complexity condition, and made judgements regarding which of two symbols was numerically ‘larger’. When novel symbols were ordered by spatial complexity, learning was facilitated. These findings showed that the spatial complexity and relational information of symbols may mediate the construction of ordered representations. This suggests that a common cognitive representation underlies all ordinal lists. Overall, the findings of this research indicate that a more nuanced account of the MNL representation is required, particularly in terms of ordinal relationships between numbers. The findings also suggest that the NP task measures ordinal lists more generally. Arguably, the way in which ordered lists are learned, combined with the relative relationships between symbols, may account for performance on the NP task, and the MNL metaphor should be extended to account for these ordinal relationships.

Intimate partner violence (IPV) is a widespread problem. Worldwide, 1-in-3 women have experienced some form of violence in their lifetime, and the majority of incidents are the result of male perpetrated IPV. Scholars suggest that objectification facilitates IPV, because the phenomenon involves perceiving and/or treating a person as an object or not as fully human. Despite these theoretical claims, objectification has not been studied extensively in the realm of heterosexual romantic relationships – the most common setting for women to experience violence. The purpose of this thesis was to explore how objectification among heterosexual men relates to the perpetration of physical, sexual, and psychological IPV within romantic relationships. I divided the study of objectification into two distinct, but complementary approaches – examining the phenomenon from implicit (Study 1 and 2) and explicit (Study 3) standpoints. Two correlational studies investigated objectification implicitly by measuring the extent to which men associated women and romantic partners with objects and/or animals. A third behavioural experiment investigated objectification explicitly by measuring the extent to which manipulating the phenomenon facilitated male physical aggression towards the romantic partner, and impacted on judgments about the objectified target’s humanness, mind, and moral status (referred to as personhood). Study 1 examined how automatically likening women to non-human entities (animals, objects) played a role in IPV perpetration in romantic relationships. Findings demonstrated that men who held implicitly objectifying perceptions of women were more likely to perpetrate sexual and physical IPV against their current female partner. Study 2 builds on the finding that men who objectify women are more prone to commit IPV, and examined whether the finding would replicate when assessing the objectification of an intimate partner. This study also examined the relation between partner-objectification and physical aggression, particularly in the context of provocation. Results showed that men’s tendency to implicitly perceive their romantic partner as an object predicted self-reported perpetration of physical IPV. They also revealed that objectification moderated the effect of provocation on physical aggression, whereby highly provoked men enacted more physical IPV against their female partner when they held stronger associations of that woman with objects and/or animals. Study 3 then experimentally investigated the effect of explicit partner-objectification, induced via an appearance-focus mindset, on denials of personhood to the target. This study also extended the novel correlational finding that objectification predicted physical IPV, and examined a causal link between partner-objectification and physical aggression towards the romantic partner, in the context of provocation. Results demonstrated that when the romantic partner was objectified by a focus on her physical appearance, she was stripped of her personhood and perceived as lacking humanity and mind. They also demonstrated a direct aggression-facilitating effect of partner-objectification, and of provocation, wherein these variables increased physical IPV. Together, the findings from these three studies indicate that objectification has profoundly negative manifestations and consequences for women in romantic relationships. Not only did the phenomena relate to greater male perpetrated sexual and physical IPV within romantic relationships, but men’s partner-objectification also diminished perceptions of the romantic partner as possessing full personhood, and directly and indirectly facilitated enacted physical aggression against the same partner. This thesis thus provides compelling evidence that objectification—implicit or explicit—is a likely contributor to the victimisation of women in romantic relationships. As such, our research can help inform prevention and intervention efforts to reduce this major social problem.

Many contemporary proposals of bilingualism conjecture that domain-general Executive Functions (EFs) are fundamental to language control. These proposals revolve around two main observations: the first is that bilinguals have been shown to demonstrate superior performance on tasks used to measure non-linguistic EFs, and the second is that language switching superficially appears to relate to switching between tasks (a process which has been associated with EFs) in that they both induce a Response Time (RT) cost. Critically, direct evidence for the involvement of EFs in both non-linguistic and linguistic bilingual processing have not been demonstrated, but merely speculated. In this thesis, I present a series of four analyses, where I explicitly investigate the presence of EFs in bilingual processing by expressing their impact as a set of cognitive model parameter changes to task performance. The results reveal that bilingual behaviour across both the non-linguistic and linguistic domains do not exhibit signs of EFs, but instead demonstrate the influence of other lower-level general cognitive processes. The main conclusions of this thesis are as follows: A) the putative bilingual advantage is attributed to enhanced selective attention and B) language switches are attributed to automatic bindings between language information and response. These findings are discussed in terms of their implications for current frameworks of language control and bilingualism in general.

Personality traits are the main currency of the field of personality psychology. However, historically there has been much confusion concerning the conceptualization of traits in relation to context, which remains unclear to date. Some personality psychologists have proposed that traits are internal and decontextualized dispositions that account for consistency in behaviour and experience across time and situations, whereas others have argued that traits are patterns of behaviour and experience that are contextualized and require appropriate eliciting stimuli for manifestation. Although there is a long history of research on the interplay of traits and situations, the contextualized view has received little attention and not yet been systematically examined in empirical studies. This thesis aims to evaluate the contextualized view of traits, and to clarify what is meant exactly when describing someone as high or low on a personality trait, specifically in relation to context. When we call someone an ‘extravert’, are we describing their typical patterns of behaviour and experience across all contexts, or are we describing their typical patterns of behaviour and experience in particular contexts? Among all traits, extraversion and neuroticism are perhaps the best understood in terms of eliciting stimuli—reward and threat, respectively— which have been described and incorporated in several personality theories. For this reason, they are the focus of this thesis. It is expected that traits will predict their corresponding expressions most strongly within situations containing relevant eliciting stimuli. The hypotheses were: (a) the relation between trait extraversion and patterns of state extraversion would be the strongest within contexts characterized by rewarding stimuli; and (b) the relation between trait neuroticism and patterns of state neuroticism would be the strongest within contexts characterized by threatening stimuli. A collection of four studies were designed to examine the contextualized nature of extraversion and neuroticism using different methodologies. The first study was an online survey, examining the hypotheses by asking participants to imagine their behaviour in certain context, the second one in a controlled lab environment, and the third and the fourth studies in people’s everyday life context using experience sampling methods. Across these studies, a mixture of subjective and objective measures of personality states and situations were employed. All four studies showed that extraversion and neuroticism significantly predicted state extraversion and state neuroticism, respectively, across all contexts. Meanwhile, state extraversion was significantly higher in rewarding contexts and state neuroticism was significantly higher in threatening contexts—both within-person and between-persons. However, the magnitude of the relation between trait and state extraversion, or between trait and state neuroticism, did not vary strongly across contexts. Although the results differed slightly depending on the study, the trait (extraversion vs. neuroticism), and the measure used (subjective vs. objective situation ratings), overall there was very weak evidence that trait-state associations vary across context. These findings therefore suggest trait extraversion and neuroticism are not strongly contextualized. These findings have broad theoretical implications for understanding what a trait is in relation to context. Additionally, some findings may have theoretical implications for how traits influence experiences of situations via situation perception and selection processes. Some practical implications concern the use of situation reappraisal as a coping strategy to improve people’s functioning in different contexts. Future studies could extend this thesis by examining the contextualized view in relation to other trait domains, aspects, and facets. They could also explore personality’s effects on situations more rigorously to disentangle the various mechanisms concerned with situation perception, situation selection, situation transformation, and situation evocation. Furthermore, they could apply these understanding to improve people’s wellbeing and facilitate personality change.

It is claimed that numbers are represented spatially. Evidence for this claim comes from the Spatial-Numerical Association of Response Codes (SNARC) effect. In the symbolic number SNARC effect, faster responses are found for the left/right hand for numerical judgments when a presented target number is smaller/larger than a referent. Yet little research has examined whether a SNARC-like effect is evident for non-symbolic quantities. If a non-symbolic SNARC-like effect can be demonstrated it would suggest that non-symbolic quantity is also represented spatially. This is an important issue conceptually because it may inform claims about the neurocognitive representation of symbolic number and non-symbolic quantity in the brain. The limited research that has examined the non-symbolic SNARC-like effect has used stimuli that could be translated into symbolic terms or has ignored the potential effects of individual differences by collapsing data across magnitudes during analysis. These methodological issues were addressed in the research reported in this thesis in which the results of five studies are reported to determine whether a SNARC-like effect occurs for non-symbolic stimuli. In Study 1 adults (n = 28) judged whether the quantity of a target array of dots was smaller or larger than a referent array of dots using either their left or right hand to make judgments. The referent was always 30-dots and judgment reaction times (RTs) to six different target arrays were assessed (i.e., 15, 20, 25, 36, 45 or 60-dots). Participants also completed a visuo-spatial memory (VSWM) and a math ability task. A non-symbolic SNARC-like effect was observed but no relationship between this effect and VSWM or math ability was found. The rationale of Study 2A was to reduce issues of discrimination and calibration found in Study 1 by reducing task difficult. Thereby increasing the chance of finding a non-symbolic SNARC-like effect for all participants. To investigate the degree to which the non-symbolic SNARC-like effect is affected by the ratio between the referent and target arrays, in Study 2A adults (n = 26) compared target arrays that were either 15 or 60 dots with a referent array of 30 dots (i.e., ratios of 0.5). They also completed VSWM and math tasks. A non-symbolic SNARC-like effect was observed which was related to VSWM. Participants who showed a more pronounced non-symbolic SNARC-like effect showed better VSWM performance. Study 2B investigated if a more pronounced non-symbolic SNARC-like effect occurs for targets closer in magnitude to the referent. The rationale was to see whether, as in the symbolic SNARC effect, non-symbolic quantity stimuli that result in slower RTs tend to elicit a stronger SNARC-like effect. The referent was 30 dots and the target arrays either 20 or 45 dots (ratios of 0.66). Adults (n = 39) completed the non-symbolic judgment, VSWM, and math tasks. Compared to Study 2A, a more pronounced non-symbolic SNARC-like effect was found. The symbolic SNARC effect has been found for other response modalities (i.e. eyes, feet). Study 2C (n = 18, adults) aimed to determine if the non-symbolic SNARC-like effect transfers to another response modalities (i.e. feet) and the degree to which responses are influenced by the surface area of the dot stimuli, in Study 2C referent and target dot arrays had the same total surface area. A non-symbolic SNARC-like effect was found in this study, which suggests that total dot surface area was not the driver of the SNARC effect found in Experiments 1, 2A, 2B and 2C. The rationale for Study 3 was to specifically address individual differences in calibration and discrimination for the non-symbolic SNARC-like effect found in Studies 1 and 2. Study 3 (n = 87) aimed to investigate the claim that individual differences in the Weber fraction may explain non-symbolic SNARC-like effect judgments using an adaptive staircase to measure the Weber fraction. This Weber threshold was then used calibrate the optimal ratio of referent-to-target for each participant. In the non-symbolic quantity judgment task one of six referents (10, 20, 30, 40, 50 or 60 dots), each being paired with an ‘easy’ (twice threshold) and a ‘hard’ (at threshold) (n = 11 – 100 dots) target. However, findings did not support this claim as participants with low and high-performance numerical acuity showed a similar non-symbolic SNARC-like effect. The findings showed a consistent non-symbolic SNARC-like effect. The pattern of findings suggests the non-symbolic SNARC-like effect is robust as it was shown across all five studies and was resistant to manipulations of ratio, visual cues, and modality of response. Differences in discrimination and calibration were found for numerical judgments suggesting there are individual differences in the spatial representation of non-symbolic quantities. Moreover, individual differences in the spatial representation of non-symbolic quantities may be related to structural differences in the brain. This confirms the importance of the non-symbolic SNARC-like effect for models of numerical cognition providing evidence that non-symbolic quantity is represented spatially from smallest to largest, left to right akin to a symbolic mental number line. This suggests that neurocognitive systems may represent symbolic number and non-symbolic quantity in the brain in a similar manner. This finding has potential implications for education and interventions for those with dyscalculia.

Wechsler Adult Intelligence Scale – Fourth Edition (WAIS-IV) is the most commonly used instrument for the assessment of cognitive abilities, and in making high-stakes decisions in Australia. The current thesis comprises four studies related to the validity of using WAIS-IV in cognitive assessment. The norms for the WAIS-IV used in Australia are based on the US standardization sample. The Woodcock Johnson III (WJ III) battery has been normed for Australian population under the age of 22. This study investigated the score equivalence of the WAIS-IV and the WJ III cognitive test battery in an Australian university student sample. One hundred and sixty-four participants, of whom 38 undertook both tests, were assigned to tests in a blocked, random order. Scores from all, and from those aged less than 22 years, were analysed. The Full Scale Intelligence Quotient of the WAIS-IV was significantly higher than the WJ III General Intellectual Ability score in every analysis. The effect sizes were medium and large in the independent and repeated measure analyses respectively. We argue for norming of the WAIS-IV, or any test used for high-stakes assessment, for Australian population to ensure fairer decisions. In the second study a five-factor model was found that fitted the WAIS-IV U.S. 15-indicator standardization samples for the nine age-groups between 16 and 69 years (N for each group = 200). A strong metric invariance for three of the five factors and a partial intercept invariance for the remaining two was established. Pairwise comparisons of adjacent age groups supported the inference that cognitive-trait group differences are manifested by group differences in the test scores. The third study sought a common model for a clinical sample of scores (N= 321) and the standardization samples. The clinical sampled differed from the standardization samples in that (a) the heterogeneous clinical sample comprised scores from patients, aged 16 to 91, with disparate neurological diagnosis in contrast to the nine age-group stratified standardization samples, (b) only the 10 core subtests were administered in the clinical sample, and (c) the clinical sample had missing data. We found (a) a difference in response strategy between the clinical and non-clinical sample, but (b) a weak factorial invariance of a five-factor measurement model across the clinical and standardization samples. We argue that the results do not disconfirm the hypothesis that the same five latent abilities found in the analysis of the 15 subtest scores in the standardization samples underlie the scores in the clinical population. In the fourth study six models from prior studies were used to generate Monte Carlo simulation data to assess sampling variation in outcomes when model misspecification is restricted to the alternate models canvassed for WAIS-IV. We found that (a) the fit of most models to samples from the different populations were good, (b) the estimated value of a parameter unrelated to the variables germane to the misspecification is true to the population value, (c) increased sample size slightly improved RMSEA, and had minimal effect on parameter estimates, (d) the average fit measures in estimations with and without warnings were not different, (e) the number of replications had minimal effect on the fit and the estimated parameter values. The results suggest that (a) post hoc modification to improve fit in a single sample is difficult to justify, (b) even in an ill-fitting model the estimates of parameters unrelated to the misspecification may be accurate, and (c) theoretical insight and heuristic reasoning aid the identification of problematic parameters.

It has been argued that early math ability rests on two core, putatively innate, number systems: a precise small number system that allows an accurate and rapid apprehension of the numerosity of small sets (i.e., subitizing), and an approximate magnitude representation that allows discrimination between quantities. Moreover, differences in core number systems functioning are claimed to underlie differences in math ability. It is, furthermore, claimed that non-symbolic magnitude representations scaffold symbolic magnitude representations and ipso facto, math abilities. While these claims are frequently made, evidence in support of them is less than convincing. One difficulty in clarifying the relationships between the two magnitude representations, or core number and maths abilities, is the large inter-individual variation in these abilities in young children which may obscure the relationships between them. Most research that has examined this issue has used variable-oriented analytic methods that treat variance as error or noise. It is proposed herein that using a person-centred analytic method (i.e., latent profile modelling) to explicate the variance may allow identification of different ability patterns (latent profiles) that reside within the overall variance distribution and, in turn, provide a more nuanced developmental model of numerical cognition. To this end, three studies were conducted that focus on the significance of different patterns of non-symbolic–symbolic magnitude representations (Studies 1 and 2), and the relationship between these patterns and different patterns of the apprehension of small sets (Study 3). In Study 1(a), 124 five- to seven-year-old children completed non-symbolic and symbolic magnitude judgement tasks, cognitive measures often associated with math ability (visuo-spatial working memory [VSWM], naming Hindu-Arabic numbers and processing speed) as well as transcoding, and a single digit addition (SDA) test. A latent profile analysis (LPA) of the magnitude judgment accuracies and response times revealed four different patterns of non-symbolic–symbolic magnitude ability relationships residing within the overall variance distribution. The cognitive measures were related to the four profiles in different ways; and the profiles predicted differences in SDA and transcoding abilities. In Study 2(b), a partial replication of Study 1, 109 five- to six-year-old children completed the same tasks as Study 1 twice–one year apart. Latent transition analysis, a longitudinal extension of LPA, examined change and stability patterns in the four profiles over time. Similar to Study 1, the findings showed the patterns were differentially associated with cognitive and math abilities. Study 3 examined the relationship between non-symbolic–symbolic magnitude ability patterns and small precise number ability patterns. The findings replicated those of Studies 1 and 2, and also showed an overlap in the two core number abilities. While only VSWM and magnitude ability patterns predicted SDA abilities (over and above small precise number abilities); both magnitude ability and small precise number ability patterns predicted single-digit subtraction abilities over and above the other cognitive factors. In summary, the findings reported herein confirm the existence of different magnitude ability relation patterns which are differentially associated with different cognitive and math abilities. Examining the change/stability pathways in these ability patterns may reveal typical and atypical pathways of math development. It is evident that different magnitude ability relation patterns partially overlap with the small precise number ability patterns. Nonetheless, differences in the patterns in the two core number indices, along with differences in cognitive indices, predict different math abilities (i.e., single-digit addition and subtraction). The overall pattern of findings is discussed in terms of a more nuanced model of numerical cognition, as well as the value of the findings for specifying diagnostic markers of early math difficulties. (a) Chew, C. S., Forte, J. D., & Reeve, R. A. (2016). Cognitive factors affecting children’s nonsymbolic and symbolic magnitude judgment abilities: A latent profile analysis. Journal of Experimental Child Psychology, 152, 173-191. https://doi.org/10.1016/j.jecp.2016.07.001 (b) Chew, C. S., Forte, J. D., & Reeve, R. A. (2019). Implications of change/stability patterns in children’s non-symbolic and symbolic magnitude judgement abilities over one year: A latent transition analysis. Frontiers in Psychology, 10, 441. https://doi.org/10.3389/fpsyg.2019.00441

Our choices can often be biased in systematic ways. In this thesis, we study the cognitive mechanisms driving two prominent choice biases: the endowment effect and the descriptive norm effect. The endowment effect, a tendency to assign higher value to something you own, is typically explained based on loss aversion. A finding that the endowment effect reverses for choices between undesirable options has been taken as evidence against loss aversion. We find that these reversals are driven by people’s expectations and only seem to occur when comparisons between the options are limited. We outline a model of loss aversion that can qualitatively and quantitatively account for these results. The descriptive norm effect, a bias towards popular options, is typically explained based on the fact that descriptive norms offer useful information as to which option is best. We show that descriptive norm effects occur even when the norm is entirely arbitrary and thus offers no useful information. Another prominent explanation of the descriptive norm effect, self categorization theory, can explain the impact of these arbitrary norms. However, this theory predicts that people will avoid conforming to descriptive norms from an outgroup. We find this not to be the case, with participants’ preferences shifting towards outgroup descriptive norms. We discuss how mechanisms from the broader choice bias literature could in principle explain our findings.