Sensory augmentation can be used to assist in some tasks where sensory information is limited or sparse. This thesis focuses on the design and investigation of a head-mounted vibrotactile sensory augmentation interface to assist navigation in low visibility environments such as firefighters’ navigation or travel aids for visually impaired people. A novel head-mounted vibrotactile interface comprising a 1-by-7 vibrotactile display worn on the forehead is developed. A series of psychophysical studies is carried out with this display to (1) determine the vibrotactile absolute threshold, (2) investigate the accuracy of vibrotactile localization, and (3) evaluate the funneling illusion and apparent motion as sensory phenomena that could be used to communicate navigation signals. The results of these studies provide guidelines for the design of head-mounted interfaces. A 2nd generation head-mounted sensory augmentation interface called the Mark-II Tactile Helmet is developed for the application of firefighters’ navigation. It consists of a ring of ultrasound sensors mounted to the outside of a helmet, a microcontroller, two batteries and a refined vibrotactile display composed of seven vibration motors based on the results of the aforementioned psychophysical studies. A ‘tactile language’, that is, a set of distinguishable vibrotactile patterns, is developed for communicating navigation commands to the Mark-II Tactile Helmet. Four possible combinations of two command presentation modes (continuous, discrete) and two command types (recurring, single) are evaluated for their effectiveness in guiding users along a virtual wall in a structured environment. Continuous and discrete presentation modes use spatiotemporal patterns that induce the experience of apparent movement and discrete movement on the forehead, respectively. The recurring command type presents the tactile command repeatedly with an interval between patterns of 500 ms while the single command type presents the tactile command just once when there is a change in the command. The effectiveness of this tactile language is evaluated according to the objective measures of the users’ walking speed and the smoothness of their trajectory parallel to the virtual wall and subjective measures of utility and comfort employing Likert-type rating scales. The Recurring Continuous (RC) commands that exploit the phenomena of apparent motion are most effective in generating efficient routes and fast travel, and are most preferred. Finally, the optimal tactile language (RC) is compared with audio guidance using verbal instructions to investigate effectiveness in delivering navigation commands. The results show that haptic guidance leads to better performance as well as lower cognitive workload compared to auditory feedback. This research demonstrates that a head-mounted sensory augmentation interface can enhance spatial awareness in low visibility environments and could help firefighters’ navigation by providing them with supplementary sensory information.

The thesis begins with accounts of various models of discrimination and of previous studies of sequential effects. It is mainly concerned with the study of discriminations in serial response tasks in which the difficulty of the discriminations varies from trial to trial. All the experiments reported were concerned with the discrimination between two lines of different length which were presented simultaneously in a display. There were always two levels of difficulty of discrimination, which were mixed in random sequence. The first two experiments demonstrated that the RT's to displays were affected by the average difficulty of the preceding displays ("local difficulty bias effect"). In Experiments 3, 4, 5 and 7 it was shown that the overall difficulty of a run of displays also affected the mean RT to all the displays in a run ("overall difficulty bias effect"). It was seen that the direction in which the RT's were affected by local difficulty bias was sometimes different from the direction of the effect of overall difficulty bias, suggesting that subjects may be aware of both local and overall average difficulty levels. Experiments 4, 5 and 6 showed that instructions to be fast modified the effects of bias, but that instructions to be cautious did not increase the effect of bias. Experiment 7 investigated the effect of increasing the actual difference between the easy and difficult discriminations - but was rather inconclusive. In Experiment 8 the RSI was varied and showed no major effect on local difficulty bias, showing that these effects were due to other factors than the time between trials. It also supported an hypothesis considered in earlier experiments that when a criterion is not being used (either during the interval between decisions, or while another criterion is being used) it will drift towards a value that will give rise to more cautious decisions. When displays were easy to discriminate subjects were able to track their speed to the errors they made, but they were not able to do so when the discriminations were more difficult. Whether the displays were easy or difficult, subjects were able to track their speed to the average difficulty of the displays. In general, as the average difficulty of the displays increased ( as the proportion of difficult displays in a mixed run of easy and difficult displays increased ), so the mean RT of the immediately following displays became slower (local effect). It was suggested that subjects' adjustments in performance which were induced by difficulty bias or instructions could be explained by changes in the values of criteria.

Human colour perception is mediated by multiple factors. These include: the external environment, physiological structures within the eye, and the neuronal pathways that originate in the eye. The aim of this thesis was to further investigate the impact of three main factors on both the perception and cortical representation of colour. These factors were: the external, changing seasonal environment, genetically determined differences in the number of photoreceptor types, and spatial filters inherent to cortical and pre-cortical luminance and chromatic pathways. Novel findings and methods were demonstrated in this thesis: 1) For the first time, it was found that natural seasonal changes in the chromatic environment (in York, UK) affect the perception of unique yellow; this finding supports the existence of a slow normalisation mechanism, which is governed by changes in the average chromatic environment. 2) Genetically atypical individuals, who have fewer photoreceptor types (dichromats), demonstrated no differences in achromatic contrast discrimination thresholds compared to colour-normal trichromats. Therefore, for this particular measure, dichromats do not appear to benefit from increased neuronal resources from ‘unused’ chromatic pathway populations. A multi-channel LED system was developed to allow the isolation of photoreceptor responses in individuals with an additional photoreceptor type (tetrachromats). Modelling of this system indicated that precision in the cone spectra used to generate the stimulus, relative to the observer’s actual cone sensitivities (i.e. peak wavelength sensitivities), is crucial for successful isolation of the cones. 3) fMRI-based population receptive field (pRF) mapping was used to measure pRF sizes in the pre-cortical channels. Between the pathways, no differences in pRF sizes were found, however, differences in fMRI measures of spatial frequency sensitivity were observed. These data indicate that spatial frequency tuning in early visual cortex may be decoupled from population receptive field sizes.

How does the brain represent sensory input? When stimuli move across sensor surfaces, such as a light source moving across the retina, sound moving between the ears, or contact moving over the skin, patterns of activation propagate across sheets of neurons that form the primary sensory cortices. Understanding how the movement of stimuli across the sensor surfaces relates to the activation of the cortical sheet is a fundamental problem in neuroscience. The thesis presents a series of computational neuroscience studies, addressing how sensory stimuli are represented in mammalian primary sensory cortex. Each study constructed a model of how tactile stimuli, experienced by rodents via the array of facial whiskers, are encoded in the barrel cortex area of the primary somatosensory cortex. Each explains how the responses of cortical neurons to sensory stimuli can be predicted from their location in the cortical sheet. In each case, simple organising principles, based on cortical connection geometry and/or local learning rules, could account for how neuronal responses vary according to sensory stimuli. The success of these highly simplified descriptions of cortical circuitry at explaining complex neurophysiological data suggests an important role for sensory experience and neural inter-connection geometry in neural computation. The roles of both have been largely overlooked in recent large-scale efforts to model somatosensory cortical processing, which have focussed instead on cataloguing descriptions of neural tissue in increasing levels of detail. Using a top-down approach to modelling, the thesis generates specific hypotheses about the functional organisation of the sensory cortex, that can be used to guide future experimental work. The contribution of the thesis will therefore have been to lay the foundations of a theoretical framework for studying tactile stimulus processing in the somatosensory cortex, which is emerging as one of the most popular model systems in modern neuroscience.

Synaesthesia is a condition in which perceptual or conceptual stimulation in one modality leads to additional experiences within the same or different modality. In grapheme-colour synaesthesia achromatic letters or numbers elicit secondary synaesthetic colour experiences while in mirror-touch synaesthesia observing touch to another person results in tactile sensations on a synaesthete’s own body. This thesis examines broader differences in personality and social perception associated with synaesthesia and investigates neural mechanisms underlying social perception in typical adults. Firstly, an association between grapheme-colour synaesthesia and personality traits was examined which revealed an altered personality profile in this group. Additionally grapheme-colour synaesthesia showed typical and (in some cases) superior social perception abilities relative to typical adults which most likely reflects wider perceptual differences related to sensitivity to high spatial frequency information previously found in this group. Secondly, an investigation into the wider consequences of mirror-touch synaesthesia revealed that the presence of this form of synaesthesia is linked with lower levels of alexithymia relative to typical adults and lower interoceptive sensitivity relative to grapheme-colour synaesthetes and controls. This thesis also explored the neural mechanisms underlying social perception in typical adults using non-invasive transcranial alternating current stimulation. This revealed that enhancing occipital gamma oscillations facilitates facial anger perception offering a new avenue to examine the neural mechanisms underlying social perception advantage in synaesthesia. Current findings are discussed in the context of existing literature on synaesthesia and social perception.

Although grapheme-colour synaesthesia is a well-characterized phenomenon in which achromatic letters and/or digits involuntarily trigger specific colour sensations, its underlying mechanisms remain unresolved. Models diverge on a central question: whether triggered sensations reflect (i) an overdeveloped capacity in normal cross-modal processing (i.e., sharing characteristics with the general population), or rather (ii) qualitatively deviant processing (i.e., unique to a few individuals). We here address this question on several fronts: first, with adult synaesthesia-trainees and second with congenital grapheme-colour synaesthetes. In Chapter 3, we investigate whether synaesthesia-like (automatic) letter-colour associations may be learned by non- synaesthetes into adulthood. To this end, we developed a learning paradigm that aimed to implicitly train such associations while keeping participants naïve as to the end-goal of the experiments (i.e., the formation of letter-colour associations), thus mimicking the learning conditions of acquired grapheme- colour synaesthesia (Hancock, 2006; Witthoft & Winawer, 2006). In two experiments, we found evidence for significant binding of colours to letters by non-synaesthetes. These learned associations showed synaesthesia-like characteristics despite an absence of conscious, colour concurrents, correlating with individual performance on synaesthetic Stroop-tasks (experiment 1), and modulated by the colour-opponency effect (experiment 2) (Nikolic, Lichti, & Singer, 2007), suggesting formation on a perceptual (rather than conceptual) level. In Chapter 4, we probed the nature of these learned, synaesthesia-like associations by investigating the brain areas involved in their formation. Using transcranial Direct Current Stimulation to interfere with two distinct brain regions, we found an enhancement of letter-colour learning in adult trainees following dlPFC-stimulation, suggesting a role for the prefrontal cortex in the release of binding processes. In Chapter 5, we attempt to integrate our results from synaesthesia-learners with the neural mechanisms of grapheme-colour synaesthesia, as assessed in six congenital synaesthetes using novel techniques in magnetoencephalography. While our results may not support the existence of a “synaesthesia continuum,” we propose that they still relate to synaesthesia in a meaningful way.

The central theme of this thesis was to examine different aspects related to the observation and judgement of emotions from the body movement and voice of two actors engaged in social interaction. There were four major goals related to this theme. The first goal was to create a novel stimulus set for the study of emotional social interactions. The second was to validate the created stimulus set by examining emotion perception in ways similar to that done with single actor displays. The third goal was to examine the effect of degrading visual and auditory information on the perception of emotional social interactions. The final goal was focused on the multimodal integration of emotional signals from body movement and voice. Initially, a stimulus set was created that incorporated body movement and dialogue between two actors in brief, natural interactions that were happy, angry or neutral at different levels of intensity. The stimulus set was captured using a Vicon motion and voice capture system and included a group of nine professional and non-professional actors. This resulted in a corpus of 756 dyadic, multimodal, emotional interactions. A series of experiments were conducted presenting participants with visual point-light displays, auditory voice dialogues or combinations of both visual and auditory displays. Observers could accurately identify happy and angry interactions from dyadic displays and voice. The intensity of expressions influenced the accuracy of the emotional identification but only for angry rather than happy displays. After validation of the stimulus set, a subset was selected for further studies. Various methods of auditory and visual distortion were tested separately for each modality to examine the effect of those distortions on recognition of emotions from body movement and voice. Results for dyadic point-light displays followed similar findings from single actor displays that inversion and scrambling decreased the overall accuracy of emotion judgements. An effect of viewpoint was also found, indicating that observation of interaction from a side viewpoint was easier for emotion detection than observation of interaction from an oblique viewpoint. In the case of voice, methods of brown noise and low-pass filtering were shown to degrade emotion identification. However, with both visual and auditory methods of distortion, participants were still able to identify emotions above the level of chance, suggesting high sensitivity to emotional cues in a social context. In the final set of studies, the stimulus set was used in a multimodal context to examine the perception of emotion from movement and voice in dyadic social interactions. It was repeatedly found that voice dominated body movement as a cue to emotions when observing social interactions. Participants were less accurate and slower in emotion discrimination when they were making judgements from body movement only, compared to conditions when movement was combined with dialogue or when dialogue was presented on its own. Even when participants watched emotionally mismatched displays with combined movement and voice, they predominantly oriented their responses towards the voice rather than movement. This auditory dominance persisted even when the reliability of the auditory signal was degraded with brown noise or low-pass filtering, although visual information had some effect on judgements of emotion when it was combined with a degraded auditory signal. These results suggest that when judging emotions from observed social interactions, we rely primarily on vocal cues from conversation rather than visual cues from body movement.

Previous research from the Sussex Ingestive Behaviour Group suggests that satiety beliefs generated by product information and satiety-relevant sensory characteristics (thick consistency and creamy flavours) can enhance the satiety response to covertly added energy in beverages. However these characteristics in low-energy beverages can generate rebound hunger effects. This thesis explored whether this enhanced-satiety concept can be translated to real consumers. Study 1 examined the extent of energy reduction that could be tolerated without rebound hunger effects. The original enhanced satiety concept was not replicated, although there was tentative evidence that energy compensation was more accurate for small energy additions. Study 2 explored whether enhanced satiety would prevail following repeated exposures in consumers' own homes. Enhanced satiety was found before and after exposure. Additionally focus groups suggested that diet-concerned consumers may be particularly interested in such products. Therefore in Study 3 this population, represented in the literature by those reporting high dietary restraint, was studied suggesting that those high in restraint and disinhibition compensated more accurately for energy in unenhanced beverages. A final complication for consumers is that believed healthy foods are often overconsumed. Two final studies demonstrated that health labels generated beliefs about the sensory experience and expected satiation and satiety of beverages. Tasting overrode the effects of these beliefs, although expectation-experience congruency led to assimilation of healthy beliefs, and indulgent-based fullness. Portion size selection was unaffected. Together the findings from these studies suggest that the enhanced satiety concept may have some utility in the real world, although it remains unclear as to how little caloric content can be tolerated whilst still enhancing satiety, and whether diet concerned consumers would benefit. Finally whilst health information may have a role in appetite expectations the interaction with sensory experience is important for generating overall product evaluations, and sensory experience is likely to override label information in dictating portion size selection.

Bibliography: leaves 402-421 / xxvii, 421 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Psychology, 1984

Seligman's theory that phobias are biologically prepared associations is challenged on theoretical and empirical grounds. It is argued that a concept of experiential preparedness may be more useful for approaching the problem of selectivity in phobias. The experimental part of the thesis pursues this argument by investigating the magnitude and habituation of electrodermal orienting responses (ORs) to words denoting ontogenetically fear-relevant (phobic) or neutral stimuli. In experiment 1 no differences between the ORs to moderately feared and neutral stimuli were found. In experiment 2 subjects were presented with stimuli as in experiment 1 and were threatened by electric shock; the phobic stimuli then elicited larger and more slowly habituating ORs than the neutral stimuli. In the following three experiments, subjects were presented with stimuli they reported as not feared but of which the majority of their peers reported substantial fears. In experiment 3 there was no manipulation of the state of the subject, in experiment 4 subjects were under threat of shock, and in experiment 5 they anticipated pleasant music. Only in experiment 4 did subjects show larger and more slowly habituating ORs to phobic than neutral stimuli. In the last two experiments, pleasant stimuli were administered while subjects anticipated shock or music. On the whole, no differences in ORs to pleasant and neutral stimuli were found under either of the two conditions. The results suggest that the OR is not simply linked to the detection of stimulus change or significance and depends on the state of the subject, with stimuli known to be associated with fear taking precedence in processing when subjects anticipate threat. As phobias are assumed to be learned responses and the OR has important implications for learning it is concluded that phobic responses towards stimuli feared in the culture may be formed when people perceive the future as threatening and unpredictable.