The minimal computational substrate of fluid intelligence

The quantification of cognitive powers rests on identifying a behavioural task that depends on them. Such dependence cannot be assured, for the powers a task invokes cannot be experimentally controlled or constrained a priori, resulting in unknown vulnerability to failure of specificity and generalisability. Evaluating a compact version of Raven's Advanced Progressive Matrices (RAPM), a widely used clinical test of fluid intelligence, we show that LaMa, a self-supervised artificial neural network trained solely on the completion of partially masked images of natural environmental scenes, achieves human-level test scores a prima vista, without any task-specific inductive bias or training. Compared with cohorts of healthy and focally lesioned participants, LaMa exhibits human-like variation with item difficulty, and produces errors characteristic of right frontal lobe damage under degradation of its ability to integrate global spatial patterns. LaMa's narrow training and limited capacity -- comparable to the nervous system of the fruit fly -- suggest RAPM may be open to computationally simple solutions that need not necessarily invoke abstract reasoning.Comment: 26 pages, 5 figure

An Experiment in Teaching Cognitive Systems Online

In Fall 2014 we offered an online course CS 7637 Knowledge-Based Artificial Intelligence: Cognitive Systems (KBAI) to about 200 students as part of the Georgia Tech Online MS in CS program. We incorporated lessons from learning science into the design of the project-based online KBAI course. We embedded ~150 microexercises and ~100 AI nanotutors into the online videos. As a quasi-experiment, we ran a typical inperson class with 75 students in parallel, with the same course syllabus, structure, assignments, projects and examinations. Based on the feedback of the students in the online KBAI class, and comparison of their performance with the students in the inperson class, the online course appears to have been a success. In this paper, we describe the design, development and delivery of the online KBAI class. We also discuss the evaluation of the course

Auditory inspection time and intelligence

This thesis studied the association between auditory inspection time (AIT) and psychometric measures of verbal and non-verbal cognitive abilities. I review attempts to search for basic information processing components that predict intelligence (Chapter 1), attempts to relate auditory processing speed to intelligence (Chapter 2), and attempts to relate acuity of sensory discrimination to intelligence (Chapter 3). These reviews establish certain essential requirements for a plan of research on auditory inspection time. Chapter 4 described the development of a modified AIT test. In a study of 120 undergraduates, the modified AIT test showed improved subject performance characteristics over previous AIT tasks, and AIT thresholds had low to moderate correlations with visual IT thresholds and with verbal and non-verbal cognitive ability scores. Chapter 5 described two studies. Study 1 included 84 undergraduates and showed that the AIT test had a very high split-half reliability and that about two-thirds of subjects who could perform the AIT task had response performance curves which fitted a cumulative normal ogive. The association between AIT and verbal ability appeared stronger than the AIT-non-verbal ability association in 34 of the subjects; this was also found in Study 2 which tested 119 11-year-olds. Unspeeded pitch discrimination showed a small but significant association with verbal ability in children but not in undergraduates. Results from neither study supported the suggestion that pitch discrimination was the basis for the AIT-cognitive ability association. Chapters 6 and 7 examined the associations among AIT, unspeeded pitch discrimination and an auditory backward masking recognition task which was dubbed the 'Raz' task. It was found that all three tasks were reliable, prone to practice effects and showed high intercorrelations. The AIT and Raz tasks appeared to share common variance not related to pitch discrimination. In a confirmatory factor analysis of over 100 13-year-olds latent variables from the three auditory tests representing auditory processing speed and pitch discrimination both had significant associations with a factor common to verbal and non-verbal intelligence, though speed was the more important factor. Chapter 8 reported the results of a longitudinal study of AIT and cognitive ability in over 100 children from age 11 to age 13. Using structural modelling techniques to create competing causal models and then testing these for goodness-of-fit to the data, some support was found for the suggestion that auditory processing abilities at age 11 might have a causal influence on later verbal and non-verbal abilities rather than the converse. Chapter 9 provided a thematic resume of the studies conducted in the thesis. It was concluded that the corrected AIT-cognitive ability association was in the region of -0.5, and that some progress had been made in explaining this association. In addition, a strong plea was made for AIT and visual IT to be integrated with other models of auditory and visual information processing which exist. Suggestions were made for future research on auditory and visual processing and intelligence

Verbal comprehension after brain damage :a psycholinguistic investigation with special reference to cerebro-vascular accident

PhD ThesisA review of theory and practice in the examination of verbal comprehension in brain-dairiaged adults leads to the conclusion that this underdeveloped area of study can benefit from the application of theories from linguistics. An experimental investigation of (principally) adults who had suffered cerebro -vascular accident applied, amoxigst other linguistic theories, the division of language into phonological, syntactic and semantic levels of organization. The main findings were: a) Semantic abilities in speech and comprehension corresponded; syntactic abilities in speech corresponded with those in reading comprehension, but not aural comprehension; comprehension of phonemic distinctions corresponded with phonetic articulatory abilities, but not with degree of phonemic paraphasia. Tests of verbal comprehension which required simple manipulations of-objects or tokens were contaminated by gesture dyspraxia. Functional comprehension was not a reliable predictor of results on linguistic tests. b) Piphasic adults with left-brain damage experienced significantly more difficulties in comprehension when sequence was critical to the meaning of a word or sentence. At the syntactic level this occurred with reading as well as with aural input, indicating a central difficulty rather than one which is modality-specific. in aural comprehension, unlike all types of control subjects including children, aphasic adults found sentences with reversible elements in surface structure harder than sentences in which reversible deep relations are not made explicit in surface structure sequence. Sequencing appears to be a significant influence on verbal comprehension after left-brain damage. c) Right-brain-damaged adults who were not aphasic in speech, and who were familial right-handers, were selectively impaired in semantic comprehension. Semantic comprehension may be bilaterally represented in the brain, although comprehension at syntactic and phonological levels may depend principally on mechanisms lateralized to the left hemisphere.Ridley Fellowship, Newcastle University

I expect, therefore I see: individual differences in visual awareness

Predictive processing theories posit that awareness of the visual world emerges as the brain engages in predictive inference about the causes of its sensory input. At each level of the processing hierarchy top-down predictions are corrected by bottom-up sensory prediction error to form behaviourally optimal inferences about the state of the visual world. Research suggests there may be individual differences in predictive processing mechanisms such that some individuals are more reliant on prior knowledge, whereas others assign more weight to sensory evidence. Predictive processing biases are thought to manifest in a range of typical and atypical perceptual experiences including proneness to perceptual illusions, sensory sensitivity in autism, and hallucinations in psychosis. The overarching aim of this thesis was to investigate whether in the general population predictive processing biases predict individual differences in visual awareness. Change blindness was selected as the central paradigm of investigation, as it can be conceptualised as a failure to incorporate a novel change into the current prediction about the state of the visual world. The empirical work in Chapter 2 aimed to characterise individual differences in visual change detection using naturalistic scenes and to identify the perceptual and cognitive measures that predict noticing ability. There were reliable individual differences in change detection that generalised to ecologically valid displays. The ability to notice visual changes was predicted by the strength and stability of perceptual predictions, as measured by the accuracy of visual short-term memory and attentional control in the face of distractors. In Chapter 3 I used voxel-based-morphometry to investigate whether inter-individual variability in brain structure predicts individual differences in visual awareness. The latter was assessed by the change blindness task as well as its strongest predictor measures (visual short-term memory, attentional capture, and perceptual rivalry). Regions of interest (ROIs) were selected in the parietal and visual cortices based on previous evidence that these areas are causally involved in the awareness of visual stimuli. This study aimed to discover whether the average grey matter density in the ROIs predict susceptibility to CB. The ROI-based analyses revealed the average grey matter density in left posterior parietal cortex predicted visual short-term memory accuracy but none of the other hypothesised relationships were significant. Chapter 4 aimed to measure individual differences in the reliance on prior knowledge by employing the Mooney face detection task. In this task participants disambiguated faces in two-tone degraded images before and after the presentation of the original versions of the images. Better change detection was predicted by Mooney face detection without any prior knowledge of the images, a measure of ‘perceptual closure’ or an ability to generate a gestalt of a scene. The attention to detail subscale of the autism spectrum also predicted superior change detection. Reliance on prior knowledge in visual perception (assessed by improvement in Mooney face detection after seeing original images) did not consistently predict atypical perceptual experiences associated with the autism spectrum or schizotypy. Chapter 5 was an investigation into, firstly, whether there is a general predictive processing bias, which manifests across different methods of inducing prior knowledge, or whether such a bias is paradigm-specific and, secondly, whether reliance on priors predicts perceptual experiences and traits. All prior manipulations in this study lead to an increased tendency to see the expected stimulus in a binocular rivalry display, except adaptation, which lead to a suppression of visual awareness. Attentional control, perceptual priming, expectancy, and imagery loaded onto a common factor, suggesting that the strength of selective attention is closely linked with the facilitatory effect of expectation. The strength of adaptation predicted superior change detection and perceptual priming predicted the propensity to experience perceptual illusions. Taken together, these findings suggest that there are reliable individual differences in visual change detection, and these are predicted by the strength of visual short-term memory representations, attentional control, perceptual closure ability, as well as the strength of low-level adaptation. Possessing expectations facilitates the entry of the corresponding percept into awareness, irrespective of the method of prior induction. The facilitatory effect that priors exert on visual awareness across different methods is closely linked with the ability to exert attentional control. This suggests that the effects of expectations on awareness may be attentional. However, predictive processing biases were method-specific in that a facilitatory effect using one prior induction method will not necessarily predict the magnitude of the effect using a different method. Some prior effects (e.g., perceptual priming, imagery, and adaptation) yielded correlations with perceptual experiences and traits in the general population. As the research in this thesis is correlational, future studies will need to delineate the effects of expectation, attention, and adaptation on visual awareness and explore the neural representations of these mechanisms

Visual working memory and ageing: do we approach cognitive tasks differently as we age?

Working Memory (WM) refers to cognitive functions that support the ready availability of a small amount of information temporarily, while we undertake ongoing actions and mental activities (e.g., Logie & Cowan, 2015), and is viewed as a core mechanism underpinning higher-order cognitive abilities. Moreover, the functioning of WM abilities is important for autonomy and wellbeing in older adults (Tomaszewski Farias et al., 2009). As assessed, WM suffers pronounced, linear decline during adult ageing (e.g., Borella, Carretti, & De Beni, 2008). However, merely establishing that younger adults outperform older adults on a given cognitive task (known as the ‘Dull Hypothesis’; Perfect & Maylor, 2000) is of limited value given that it is uninformative regarding how and why WM declines with age. This thesis was inspired by research that has suggested that some aspects of WM decline faster than others. Indeed, verbal WM appears least susceptible, and visuospatial WM most susceptible to age-related decline (Johnson et al., 2010). In six experiments, I moved beyond the ‘Dull Hypothesis’ and tested whether older adults approached WM tasks differently from younger adults, perhaps relying on relatively intact verbal abilities while performing visual memory tasks. Crucially, visual material – in everyday life as well as in memory experiments – may be remembered via verbal codes or visual traces, or both. In some WM theories, visual and verbal material is seen as maintained by separate mechanisms. The Multiple-Component model of WM (Baddeley, 1986; 2012; Baddeley & Logie, 1999; Logie, 2011) is based on the postulate that visuospatial and verbal information is stored separately in dedicated storage buffers, which may also rely on separate rehearsal mechanisms (Baddeley, 2012; Logie, 2011). If one mechanism declines more with age, perhaps older adults strategically recruit a different mechanism. This led to our central research question: Do we approach cognitive tasks differently as we age? I investigated this in several WM paradigms, as outlined below. The first series of experiments addressed the debate about whether older adults have a specific deficit in the ability to bind and remember conjunctions of features, by investigating the consequences of allowing verbal rehearsal in visual feature-binding tasks. In experiments 1 to 4, I studied the role of verbal labels in two different feature-binding paradigms to test whether discrepancies in the literature can be explained by verbal rehearsal of visual features, which might vary by age group. I found that overall, visual memory for difficult-to-label, noncategorical, visual information appeared especially limited for older adults, likely because it impedes engagement of other systems, such as verbal WM or longterm memory. Results regarding the potential implications for discrepancies in the feature-binding literature were mixed. Next, I looked at the effect of instructing or preventing verbal labelling in a continuous colour memory paradigm, using a mixture model which allowed comparison of continuous (‘visual’) and categorical (corresponding to verbal labels, e.g., ‘red’) memory representations. Labelling improved memory performance in both age groups, but older adults appeared to spontaneously rehearse verbal labels sub-vocally more than younger adults when simply instructed to perform the task in silence. Finally, I investigated the role of strategic approaches in an N-back WM training paradigm. In this study, I instructed participants to use a visualisation strategy previously found to improve N-back performance in younger adults. I found that both younger and older adults benefitted from the instructed strategy and performed better than uninstructed controls, but some evidence suggested that the strategy was more difficult to implement for older adults. I also found significant associations between N-back performance and the type, and level of detail, of self-generated strategies in the uninstructed participants. Combined, the results suggested that measures of performance and capacity partly reflect the extents to which participants apply appropriate strategies. Strategic mediation should be considered in research aiming to understand memory for visual features, continuous colour memory, and the mechanisms of WM training. Our results highlighted that strategic differences between younger and older adults may be crucial to interpret the age-related decline of memory, as measured in these paradigms, thus illustrating the importance of controlling differences in age-related strategic preferences in visual memory tasks. These differences may be informative for our understanding of age-related cognitive decline, suggesting that older adults may compensate for decline of some functions by approaching tasks differently

A comparison of working memory profiles in HIV-infected and HIV-exposed uninfected children

A thesis submitted to the Faculty of Humanities (University of the Witwatersrand, Johannesburg), in fulfillment of the requirements for the degree of Doctor of Philosophy by thesis in the field of Psychology. University of the Witwatersrand, Johannesburg, 2015Conventional psychometric measures, such as the IQ score, have significant limitations in addressing the assessment needs of linguistically and culturally diverse communities. In response, working memory assessment has been identified as a promising alternative to these constraints. It is a better predictor of scholastic success than IQ, and is essential in the acquisition of fundamental literacy and numeracy concepts in school beginners. While there is a lot of theoretical and empirical support for working memory performance in typically developing populations, less is known about its functioning in the context of atypical development; particularly in children who are infected with, or exposed to HIV in utero. This study compared the working memory (AWMA) and general neuropsychological functioning (NEPSY-II) of 273 South African school beginners (6-8 years). The sample consisted of both HIV-infected (n = 95), and HIV-exposed (n = 86) children, as well as an uninfected, unexposed typically developing control group (n = 92). Significant differences were found between the three groups on measures of working memory and general neurocognitive functioning, where the processing component of working memory appeared to be particularly impaired in the two HIV-affected atypical groups. A within-group analysis of the relative strengths and weaknesses of each of the three groups showed that both storage and processing skills in the verbal domain appeared to be general weaknesses, while visuospatial working memory was a relative strength. The former is believed to be influenced by issues of linguistic test bias in the multilingual sample, while the latter is posited to be a consequence of this very multilingualism, which affords these children an executive functioning advantage. The two HIV-affected samples also showed significant deviations in the structure of their working memory when compared to the typically developing control group. However, within-group structural comparisons of a number of working memory models showed that the four factor model comprising separate components of the verbal and visuospatial simple and processing components of working memory was still favoured, even in conditions of atypical development. The study contributes to the growing body of working memory research by presenting the working memory profiles of HIV-infected and HIV-exposed, uninfected children. It also assists in identifying HIV-exposed, uninfected children as a vulnerable and under-researched clinical group which could benefit from further intervention, as well as foregrounding working memory as a less biased alternative in the assessment of paediatric cognitive functioning.MT201