Psychology

I would like to thank Maarten Speekenbrink for his help with the statistical analysis in this thesis, W illiam Jimenez for his cooperation in running the lab experiments and all the Ipoints staff for their support in running the web-based experiments. A special thank you to N ick Chater for his guidance, ideas, feedback and encouragement which made this research possible. I, Odile Paola Robotti, confirm that the work presented in this thesis is my own. Where information has been derived from other sources, I confirm that this has been indicated in the thesis.

Transfer, the use of acquired knowledge, skills and abilities across tasks and contexts, is a key and elusive goal of learning. Most evidence available in literature is based on a limited number of tasks, predominantly open-ended problems, game-like problems and taught school subjects (e.g. maths, physics, algebra). It is not obvious that findings from this work can be extended to the domain of decision making problems. This thesis, which aims to broaden the understanding of enhancing and limiting factors of transfer, examines transfer of binary decision making problems (analogs of the Monty Hall problem) under various conditions of semantic distance between learning and target problems, contextual shifts, and delay between learning and target. Our results indicate that not all findings of the classic analogical transfer studies based on open problem solving tasks extend to binary decision making transfer. Specifically, analogical encoding (i.e. learning two analogs by comparing the...

Understanding how neurons encode and compute information is fundamental to our study of the brain, but opportunities for hands-on experience with neurophysiological techniques on live neurons are scarce in science education. Here, we present Spikeling, an open source in silico implementation of a spiking neuron that costs £25 and mimics a wide range of neuronal behaviours for classroom education and public neuroscience outreach. Spikeling is based on an Arduino microcontroller running the computationally efficient Izhikevich model of a spiking neuron. The microcontroller is connected to input ports that simulate synaptic excitation or inhibition, to dials controlling current injection and noise levels, to a photodiode that makes Spikeling light sensitive, and to a light-emitting diode (LED) and speaker that allows spikes to be seen and heard. Output ports provide access to variables such as membrane potential for recording in experiments or digital signals that can be used to excite other connected Spikelings. These features allow for the intuitive exploration of the function of neurons and networks mimicking electrophysiological experiments. We also report our experience of using Spikeling as a teaching tool for undergraduate and graduate neuroscience education in Nigeria and the United Kingdom.

As a human observer moves through the world, their eyes acquire a changing sequence of images. The information from this sequence is sufficient to determine the structure of a 3-D scene, up to a scale factor determined by the distance that the eyes have moved [1, 2]. There is good evidence that the human visual system accounts for the distance the observer has walked [3, 4] and the separation of the eyes [5-8] when judging the scale, shape and distance of objects. However, using an immersive virtual reality environment we created a scene that provided consistent information about scale from both distance walked and binocular vision and yet observers failed to notice when this scene expanded or contracted. This failure led to large errors in judging the size of objects. The pattern of errors cannot be explained by assuming a visual reconstruction of the scene with an incorrect estimate of interocular separation or distance walked. Instead, it is consistent with a Bayesian model of cue integration in which the efficacy of motion and disparity cues is greater at near viewing distances. Our results imply that observers are more willing to adjust their estimate of interocular separation or distance walked than to accept that the scene has changed in size.

Experience indicates that the sense of presence in a virtual environment is enhanced when the participants are able to actively move through it. When exploring a virtual world by walking, the size of the model is usually limited by the size of the available tracking space. A promising way to overcome these limitations are motion compression techniques, which decouple the position in the real and virtual world by introducing imperceptible visual-proprioceptive conflicts. Such techniques usually precalculate the redirection factors, greatly reducing their robustness. We propose a novel way to determine the instantaneous rotational gains using a controller based on an optimization problem. We present a psychophysical study that measures the sensitivity of visual-proprioceptive conflicts during walking and use this to calibrate a real-time controller. We show the validity of our approach by allowing users to walk through virtual environments vastly larger than the tracking space.

Dynamic learning in humans has been extensively studied using externally applied force fields to perturb movements of the arm. These studies have focused on unimanual learning in which a force field is applied to only one arm. Here we examine dynamic learning during bimanual movements. Specifically we examine learning of a force field in one arm when the other arm makes movements in a null field or in a force field. For both the dominant and non-dominant arms, the learning (change in performance over the exposure period) was the same regardless of whether the other arm moved in a force field, equivalent either in intrinsic or extrinsic coordinates, or moved in a null field. Moreover there were no significant differences in learning in these bimanual tasks compared to unimanual learning, when one arm experienced a force field and the other arm was at rest. Although the learning was the same, there was an overall increase in error for the non-dominant arm for all bimanual conditions compared to the unimanual condition. This increase in error was the result of bimanual movement alone and was present even in the initial training phase before any forces were introduced. We conclude that, during bimanual movements, the application of a force field to one arm neither interferes with nor facilitates simultaneous learning of a force field applied to the other arm.

In the field of visual attention, bottom-up or saliency-based visual attention allows primates to detect non-specific conspicuous objects or targets in cluttered scenes. Simple multiscale "feature maps" detect local spatial discontinuities in intensity, color, orientation, and are combined into a "saliency" map. HMAX is a feature extraction method and this method is motivated by a quantitative model of visual cortex. In this paper, we introduce the Saliency Criteria to measure the perspective fields. This model is based on cortex-like mechanisms and sparse representation, Saliency Criteria is obtained from Shannon's self-information and entropy. We demonstrate that the proposed model achieves superior accuracy with the comparison to classical approach in static saliency map generation on real data of natural scenes and psychology stimuli patterns.

The ratio of the length of the 2nd and 4th digits of the hand is an indicator of prenatal testosterone exposure and has been shown to be a within sex correlate of various abilities, such as visuo-spatial processing in men. However, a number of studies report such links also exist in women, whilst others show no link for either sex. Using a unique paradigm that subdivides visuo-spatial processing into a distinct subset of component skills we found a strong correlation between finger ratio and spatial memory performance specifically under stereo viewing conditions in women. We argue that the current ambiguity regarding links between digit-ratio and visuo-spatial ability is the result of a lack of clarity between the component skills recruited in different visuo-spatial tasks. Our task independently tested a subset of the component skills used in visuo-spatial tasks such as: mental rotation, cross-dimensionality processing and feature detection. Our results show that digit-ratio, a physical parameter linked to prenatal testosterone levels, indicates performance on a distinct aspect of visuo-spatial processing in women, without contradicting previous links for visuo-spatial processing in men. These results offer an explanation for the differences in previous findings linking visuo-spatial processing in both men and women.

Current theories of reasoning (Evans & Over, 1996; Sloman, 1996; Stanovich & West, 2000) propose a distinction between unschooled automatic reasoning and deliberate analytical formal reasoning. The paper critically evaluates these theories, and suggests that there is little empirical support for qualitative differences between implicit and explicit reasoning processes. Moreover, both processes share common properties, consistent with a theoretical framework developed to account for implicit learning. The review proposes that the role implicit processing plays in reasoning needs to be re-evaluated, since current dual process theories assert claims that are not empirically supported.

The present study examined how self-regulatory processes influenced problem solving behavior under conditions in which people were either re-exposed to their prior learning, or experienced someone else’s. In a series of four experiments, participants solved two complex control tasks that were identical in structure but varied in presentation format. Participants either learnt to solve the second task, based on their original learning phase from the first task, or learnt to solve the second task based on another participant’s learning phase. Experiments 1 showed that, under conditions in which participants learning phase was experienced twice, performance deteriorated in the second task compared to the first. In contrast, when the learning phases in the first and second task differed, performance improved in the second task compared to the first. Experiments 2 introduced instructional manipulations that induced the same response patterns as Experiment 1, and Experiment 3 showed that participants differentially weighted the learning phase in the second task. In Experiment 4 judgments of self-efficacy were shown to track control performance. The implications of these findings for induction, self-regulation, and insight are discussed.