Adjudicating between face-coding models with individual-face fMRI responses.

The perceptual representation of individual faces is often explained with reference to a norm-based face space. In such spaces, individuals are encoded as vectors where identity is primarily conveyed by direction and distinctiveness by eccentricity. Here we measured human fMRI responses and psychophysical similarity judgments of individual face exemplars, which were generated as realistic 3D animations using a computer-graphics model. We developed and evaluated multiple neurobiologically plausible computational models, each of which predicts a representational distance matrix and a regional-mean activation profile for 24 face stimuli. In the fusiform face area, a face-space coding model with sigmoidal ramp tuning provided a better account of the data than one based on exemplar tuning. However, an image-processing model with weighted banks of Gabor filters performed similarly. Accounting for the data required the inclusion of a measurement-level population averaging mechanism that approximates how fMRI voxels locally average distinct neuronal tunings. Our study demonstrates the importance of comparing multiple models and of modeling the measurement process in computational neuroimaging.This work was supported by the European Research Council (261352 awarded to NK), the UK Medical Research Council (MC_A060_5PR2 awarded to NK), and a British Academy Postdoctoral Fellowship (JDC)

A New Standard for Comparison Research: Uncovering the Dynamic Interactive Pattern of Comparative Judgments and its Implications.

Social judgments of the self or others are often made in comparison to some standard in the environment. How these standards influence our judgments depends heavily on their relative standing on the evaluative dimension of interest compared to the target of the judgment. Despite this consequential role, researchers have often selected items and comparison standards somewhat arbitrarily, either ignoring or simplifying their influence substantially. The current dissertation will argue that this poses serious issues for the generalisability and validity of such findings, preventing strong tests of theory. Instead, it will offer a new more holistic approach to the investigation of the comparison process which takes this key variable into account. In the first chapter, a brief overview of the comparative process and the influence of comparison standards will be given to highlight these potential issues. Chapter 2 will then show that standards with the same relative distance to the target can potentially lead to opposing comparison effects simply due to item selection alone. Chapter 3 confirms this heterogeneity at the item level, and uncovers the dynamic interactive pattern of assimilation and contrast, showing that the dichotomisation of the relative distance between target and standard into ‘Moderate’ or ‘Extreme’ standards can be problematic. Chapter 4 will show how this dynamic pattern shifts in response to other moderating variables, like a comparative focus on similarities or differences. Thereby, this chapter also offers a new paradigm that can robustly test theoretical predictions, while avoiding the aforementioned pitfalls. Finally, the last chapter will offer some concluding thoughts about the implications for the literature, limitations of the current work, and offer recommendations for future research

Sensory History Matters for Visual Representation: Implications for Autism

How does the brain represent the enormous variety of the visual world? An approach to this question recognizes the types of information that visual representations maintain. The work in this thesis begins by investigating the neural correlates of perceptual similarity & distinctiveness, using EEG measurements of the evoked response to faces. In considering our results, we recognized that the effects being measured shared intrinsic relationships, both in measurement and in their theoretic basis. Using carry-over fMRI designs, we explored this relationship, ultimately demonstrating a new perspective on stimulus relationships based around sensory history that best explains the modulation of brain responses being measured. The result of this collection of experiments is a unified model of neural response modulation based around the integration of recent sensory history into a continually-updated reference; a drifting-norm. With this novel framework for understanding neural dynamics, we tested whether cognitive theories of autism spectrum disorder (ASD) might have a foundation in altered neural coding for perceptual information. Our results suggest ASD brain responses depend on a more moment-to-moment understanding of the visual world relative to neurotypical controls. This application both provides an exciting foothold in the brain for future investigations into the etiology of ASD, and validates the importance of sensory history as a dimension of visual representation

Norm Contestation and Its Effects on Emergence of a New Norm

The objective of this study is to propose a theoretical model to investigate the mechanism by which contesting of a harmful legal norm by powerless individual actors results in the emergence of a new norm. While much work has been done on norm contestation at the “actor level” in the field, the structural conditions under which contesting of harmful norms by powerless individual actors lead to emergence of a new norm have been insufficiently studied, especially in the non-democratic cultural context. I developed a model that combine existing causal theories in one frame to reproduce observe conditions in the real world to determine necessary structural conditions for the emergence of a new norm by powerless individual actors. A modeling and simulation method and, more specifically, the theoretical model building paradigm is used to develop the model. Social identity theory and the system dynamics modeling approach are used to respectively build the conceptual model and implement the simulation model. The model is tested and compared within two types of communities: democratic and loose vs non-democratic and tight. My findings determine necessary structural conditions for the emergence of a new norm. Indeed, my model’s result show that education among others play the main role in the process of norm emergence which is consistent with the previous literature. Moreover, the model’s results demonstrate that while average-strength harmful norms can be replaced in democratic and loose societies, only weak norms can be replaced in non-democratic and tight societies. Finally, the simulation model introduces new counterfactual generated hypothesis that can be further tested through empirical studies

Determination of the Fundamental Image Categories for Typical Consumer Imagery

Many tasks in imaging science are image-dependent. While a particular dependency might simply be a function of certain physical attributes of an image, often it is closely related to the perceived semantic category. Therefore, a thorough understanding of image semantics would be of substantial practical value. The primary goal of this research was to determine the fundamental semantic categories for typical consumer imagery. Two psychophysical experiments were performed. Experiment I was a Free Sorting Experiment where observers were asked to sort 32 1 images into piles of similar images. Experiment II was a Distributed Experiment conducted over the internet which used the method of triads to collect similarity and dissimilarity data from 321 images. Due to the large number of images included in the experiment, the method of non-repeating random paths was employed to reduce the number of required responses. Both experiments were analyzed using multidimensional scaling and hierarchical cluster analysis. The Free Sorting Experiment was also analyzed using dual scaling. The results from all three methods were compiled and a set of 34 categories that proved to be stable across multiple methods of analysis was formed. A multidimensional perceptual image semantic space has been suggested and advantages to utilizing such a structure have been outlined. The 34 fundamental categories were represented by 10 perceptual dimensions that described the underlying perceptions leading to categorical assignments. The 10 perceptual dimensions were humanness, artificialness, perceived proximity, candidness, wetness, architecture, terrain, activeness, lightness, and relative age

Why We Disagree: Morality and Social Categorization

Recent research has identified important functional differences between Prescriptive morality (based in approach motivation) and Proscriptive morality (based in avoidance motivation). The purpose of the present research was to understand the consequences of these moralities applied at the group level for social categorization, especially in response to threat. I measured social categorization with a novel method in which participants categorized same-race and cross-race morphed faces. Social Justice (which is Prescriptive morality applied to the group) was associated with more inclusive social categorization under conditions of threat compared to a control condition. Social Order (which is Proscriptive morality applied to the group) was not associated with social categorization. The implications of this work for social categorization, politics, and our understanding of moral diversity are discussed