Association between weight perception and psychological distress

Background: Obesity is a well-known cause of cardiovascular disease burden and premature death, but effects on depressive symptoms remain equivocal. Depressive symptoms may be more common among the obese individuals who perceive themselves as overweight, rather than those who perceive themselves as having an acceptable weight. Our aim was to determine whether weight status and weight perceptions are independently associated with psychological distress.

Methods: We conducted a cross-sectional study using data from the Australian National Health Survey 2004–2005 (N=17 253). All variables were collected by self-report. Adjusted multinomial logistic regression analysis was conducted to generate prevalence odds ratios with 95% confidence intervals (95% CI) for medium (Kessler Psychological Distress Scale (K10) scores of 20–29) and high (K10 scores of 30–50) psychological distress (compared with K10 scores of 10–19 as the reference) associated with weight status (standard body mass index (BMI) cutoffs for underweight, overweight and obesity vs normal weight), weight perception (perceived underweight and overweight vs acceptable weight) and weight misperception (incorrect with BMI vs correct with BMI) adjusting for numerous important covariates.

Results: Overweight and underweight perception increased the odds of medium (40 and 50%) and high (50 and 120%) psychological distress, whereas weight status and weight misperception were not associated with psychological distress in adjusted analysis. Gender, alcohol consumed per week and post-school education were not significant covariates (at P<0.10 level).

Conclusions: Overweight and underweight perception rather than weight status or weight misperception are significant risk factors associated with medium and high psychological distress prevalence and effects appear to be uniform for men and women. Well-designed prospective studies are still needed to determine whether weight perceptions cause psychological distress, and if so, whether symptoms are significantly reduced following effective intervention.

Ultraviolet colour perception in European starlings and Japanese quail

Whereas humans have three types of cone photoreceptor, birds have four types of single cones and, unlike humans, are sensitive to ultraviolet light (UV, 320-400 run). Most birds are thought to have either a violet-sensitive single cone that has some sensitivity to UV wavelengths (for example, many non-passerine species) or a single cone that has maximum sensitivity to UV (for example, oscine passerine. species). UV sensitivity is possible because, unlike humans, avian ocular media do not absorb UV light before it reaches the retina. The different single cone types and their sensitivity to UV light give birds the potential to discriminate reflectance spectra that look identical to humans. It is clear that birds use UV signals for a number of visual tasks, but there are few studies that directly demonstrate a role for UV in the detection of chromaticity differences (i.e. colour vision) as opposed to achromatic brightness. If the output of the violet/UV cone is used in achromatic visual tasks, objects reflecting more UV will appear brighter to the bird. 11, however, the output is used in a chromatic mechanism, birds will be able to discriminate spectral stimuli according to the amount of reflected light in the UV part of the spectrum relative to longer wavelengths. We have developed a UV 'colour blindness' test, which we have given to a passerine (European starling) and a non-passerine (Japanese quail) species. Both species learnt to discriminate between a longwave control of orange vs red stimuli and UV vs 'non-UV' stimuli, which were designed to be impossible to differentiate by achromatic mechanisms. We therefore conclude that the output of the violet/UV cone is involved in a chromatic colour vision system in these two species.

Investigation of the intersection of constraints model of motion perception

The direction and speed of motion of a one-dimensional (1-D) stimulus, such as a grating, presented within a circular aperture is ambiguous. This ambiguity, referred to as the Aperture Problem (Fennema & Thompson, 1979) results from (i) the inability to detect motion parallel to grating orientation, and (ii) the occlusion of border information, such as the ‘ends’ of the grating, by the surface forming the aperture, Adelson and Movshon's (1982) intcrsection-of-constraints (IOC) model of motion perception describes a two-stage method of disambiguating the motion of 1-D moving stimuli (e.g., gratings) to produce unambiguous motion of two-dimensional (2-D) objects (e.g., plaid patterns) made up of several 1-D components. Specifically, in the IOC model ambiguous 1-D motions extracted by Stage 1 component-selective mechanisms are integrated by Stage 2 pattern-selective mechanisms to produce unambiguous 2-D motion signals. ‘Integration’ in the context of the IOC model involves determining the single motion vector (i.e., combination of direction and speed) which is consistent with the I-D components of a 2-D object. Since the IOC model assumes that 2-D objects undergo pure translation (i.e., without distortion, rotation, etc.), the motion vector consistent with all 1-D components describes the motion of the 2-D object itself. Adelson and Movshon (1982) propose that neural implementation of the computation underlying the IOC model is reflected in the perception of coherent 2-D plaid motion reported when two separately-moving ‘component’ gratings are superimposed. Using these plaid patterns the present thesis assesses the IOC model in terms of its ability to account for the perception of 2-D motion in a variety of circumstances. In the first series of experiments it is argued that the unambiguous motion perceived for a single grating presented within a rectangular aperture (i.e., the Barberpole illusion; Wallach, 1976) reflects application of the IOC computation to the moving 1-D grating and the stationary boundary of the aperture. While contrary to the assumption which underlies the IOC model (viz., that integration occurs between moving 1-D stimuli), evidence consistent with the involvement of the IOC computation in mediating the Barberpole illusion (in which there is only one moving stimulus) is obtained by measuring plaid coherence as a function of aperture shape. It is found that rectangular apertures which bias perceived component motions in directions consistent with plaid direction facilitate plaid coherence, while rectangular apertures which bias perceived component motions in directions inconsistent with plaid direction disrupt plaid coherence. In the second series of experiments, perceived directions of motion of type I symmetrical, type I asymmetrical, and type II plaids are measured with the aim of investigating the deviations in plaid directions reported by Ferrera and Wilson (1990) and Yo and Wilson (1992). Perceived directions of both asymmetrical and type II plaids are shown to deviate away from lOC-predicted directions and towards mean component direction. Furthermore, the magnitude of these deviations is being proportional to the difference between lOC-predicted plaid direction and mean component direction. On the basis of these directional deviations, modification to the IOC model is proposed. In the modified IOC model it is argued that plaid perception involves (i) the activity of Stage 2 pattern-selective mechanisms (and the Stage 1 component-selective mechanisms which input into these pattern-selective mechanisms) involved in implementing the IOC computation, and (ii) component-selective mechanisms which influence plaid perception directly, and ‘extraneously’ to the IOC computation. In the third series of experiments the validity of this modified IOC model, as well as the validity of alternative one-stage models of plaid perception are assessed in relation to perceived directions of plaid-induced MAEs as a function of both plaid direction and mean component direction. It is found that plaid-induced MAEs are shifted away from directions opposite to lOC-predicted plaid direction towards the direction opposite to mean component direction. This pattern of results is taken to be consistent with the modified IOC model which predicts the activity, and adaptation both of mechanisms signalling plaid direction (via implementation of the IOC computation), and ‘extraneous-type’ component-selective mechanisms signalling component directions. Alternative one-stage models which predict the adaptation of only mechanisms signalling plaid direction (the feature-tracking model), or the adaptation only of mechanisms signalling component directions (the distribution-of-activity model), cannot account for the directions of plaid-induced MAEs reported. The ability of the modified IOC model to account for the perceived directions of (i) gratings in rectangular apertures, (ii) various types of plaid in circular apertures, and (iii) directions of plaid-induced MAEs, is interpreted as supporting the proposition that human motion perception is based on a parallel and distributed process involving Stage 2 pattern-selective mechanisms (and the Stage 1 component-selective mechanisms which input into these mechanisms) taken to implement the IOC computation, and component-selective mechanisms taken to provide an 'extraneous' direct contribution to motion perception.

Conventions of pictorialism (iconic imagery, perceived space and the picture plane) deconstructed and reconstructed as alternative models of perception, embodied in paintings and drawings

This thesis is concerned with conventions of pictorialism, viz. the surface of an artwork or the plane of denotation (in my case paper, canvas or wood); and iconic imagery and the depiction of perceptual space that is connotated by marks, colours and forms upon that surface. Most importantly this thesis is concerned with the relationship between these elements and the deconstruction of them. That the reconstruction of the deconstructed language can create expressive iconic structures that perhaps contain conflicting information and elements, but are simultaneously single and self-contained perceptual models of seeing the world, and the things in it, in another way; is a major focus. The thesis is embodied in the paintings and drawings which are documented in the exegesis that follows.

Motherhood and health : perception and practice

[No Abstract]

Women's bodies, self perception and physical activity : a naturalistic study of women's participation in aerobics classes

The aim of this study was to describe the behaviour and perceptions of women in aerobic or exercise to music classes. In particular, the study examined the meaning women attach to this activity choice and the interaction of aerobics participation with cultural pressures and beliefs such as that of the ‘ideal female bodyshape’. A naturalistic method of study was chosen in order to gain a comprehensive view of the subjective experience of aerobics participation. Approximately fifty female health club members were observed over a three month period in order to identify and describe patterns of involvement, behaviour and perception and the factors affecting them. Six groups of women were identified. These were ‘Naturals’, ‘Compulsive’, ‘Functional Feminist’. Several factors were observed as potentially contributing to the patterns observed. These included attitude toward perceived cultural ideals and pressures of female expectation and shape, perceptions of aerobics and exercise, pre-occupation with slenderness and bodyshape, self-image and body image. The relationship between these factors was found to be dynamic and reciprocal, with participation possibly intensifying or alternately reducing bodyshape concern. Aerobics was seen to have a multifaceted yet very individual and important appeal to the women observed.

The effects of phonological and morphological training on speech perception scores and grammatical judgments in deaf and hard-of-hearing children

Seventeen primary school deaf and hard-of-hearing children were given two types of training for 9 weeks each. Phonological training involved practice of /s, z, t, d/ in word final position in monomorphemic words. Morphological training involved learning and practicing the rules for forming third-person singular, present tense, past tense, and plurals. The words used in the two training types were different (monomorphemic or polymorphemic) but both involved word final /s, z, t, d/. Grammatical judgments were tested before and after training using short sentences that were read aloud by the child (or by the presenter if the child was unable to read them). Perception was tested with 150 key words in sentences using the trained morphemes and phonemes in word final position. Grammatical judgments for sentences involving the trained morphemes improved significantly after each type of training. Both types of training needed to be completed before a significant improvement was found for speech perception scores. The results suggest that both phonological and morphological training are beneficial in improving speech perception and grammatical performance of deaf and hard-of-hearing children and that both types of training were required to obtain the maximum benefit.

Separating the contributions of hearing, lexical knowledge and speech production to speech perception scores in children with hearing impairments.

Open-set word and sentence speech-perception test scores are commonly used as a measure of hearing abilities in children and adults using cochlear implants and/or hearing aids. These tests are usually presented auditorily with a verbal response. In the case of children, scores are typically lower and more variable than for adults with hearing impairments using similar devices. It is difficult to interpret children's speech-perception scores without considering the effects of lexical knowledge and speech-production abilities on their responses. This study postulated a simple mathematical model to describe the effects of hearing, lexical knowledge, and speech production on the perception test scores for monosyllabic words by children with impaired hearing. Thirty-three primary-school children with impaired hearing, fitted with hearing aids and/or cochlear implants, were evaluated using speech-perception, reading-aloud, speech-production, and language measures. These various measures were incorporated in the mathematical model, which revealed that performance in an open-set word-perception test in the auditory-alone mode is strongly dependent on residual hearing levels, lexical knowledge, and speech-production abilities. Further applications of the model provided an estimate of the effect of each component on the overall speech-perception score for each child.

Stimulus determinants and receptor mechanisms involved in the tactual perception of woollen fabrics

The dimensions of touch sensations were investigated in a series of human psychophysical experiments using woollen fabrics as stimuli and words from the textile industry literature as verbal descriptors of touch sensations. Roughness was shown to be an important dimension and was found to be encoded by two out of the four receptors in the skin that respond to specific frequencies of mechanical vibration.

Risk perception, risk communication and message framing : breast cancer and family history

Examines the relationships between risk perception, risk communication, and health protective behaviour in relation to breast cancer and family history. Qualitative research was conducted to develop a printed community resource. Theoretical and practical implications for health behaviour theory and risk communication are identified.

The roles of object-image relative motion and static depth information in the perception of heading

Investigates visual information that enables human to effectively guide their movement through the environment. This problem is fundamental to the study of human behaviour, since survival is contingent upon the acquisition of resources that lie in different locations throughout the environment.