This thesis is concerned with the role of symmetry in low-level image segmentation. Early detection of local image properties that could indicate the presence of an object would be useful in segmentation, and it is proposed here that approximate bilateral symmetry, which is common to many natural and man made objects, is a candidate local property. To be useful in low-level image segmentation the representation of symmetry must be relatively robust to noise interference, and the symmetry must be detectable without prior knowledge of the location and orientation of the pattern axis. The experiments reported here investigated whether bilateral symmetry can be detected with and without knowledge of the axis of symmetry, in several different types of pattern. The pattern properties found to aid symmetry detection in random dot patterns were the presence of compound features, formed from locally dense clusters of dots, and contrast uniformity across the axis. In the second group of experiments, stimuli were designed to enhance the features found to be important for global symmetry detection. The pattern elements were enlarged, and grey level was varied between matched pairs, thereby making each pair distinctive. Symmetry detection was found to be robust to variation in the size of matched elements, but was disrupted by contrast variation within pairs. It was concluded that the global pattern structure is contained in the parallelism between extended, cross axis regions of uniform contrast. In the third group of experiments, detection performance was found to improve when the parallel structure was strengthened by the presence of matched strings, rather than pairs of elements. It is argued that elongation, parallelism, and approximate alignment between pattern constituents are visual properties that are both presegmentally detectable, and sufficient for the representation of global symmetric structure. A simple computational property of these patterns is described.

Natural variability can make different instances of the same face appear remarkably dissimilar. Such variability rarely affects familiar face recognition. However, small differences in appearance between encounters can have really detrimental effects on identifying instances of unfamiliar faces as the same person. In typical face processing research, within-person variability is experimentally controlled, in order to explore the influences of between-person variability in face processing directly. That is, face stimuli are constrained so that differences between individual faces are restricted to identity-specific information; shape and texture. To this end, it remains unclear whether such natural variability plays a part in normal face processing. In this thesis, a series of experiments explore whether experiencing natural variability is beneficial in normal face processing. Specifically, the experiments described within this thesis address whether there is a role of within-person variability in face learning, with various manipulations, and also whether it has a role in improving unfamiliar face matching. The results suggest that experiencing variability is important in face learning – specifically in developing stable face representations. It was also found to be beneficial in improving unfamiliar face matching. Additional manipulations, such as the presence of additional person information, did not show any additional benefit to face learning – unlike previous studies. I suggest that the differences between the results observed here and previous studies highlight differences in measures of familiarity, and the importance of considering what different measures tell us about face processing. I discuss these findings in relation to previous face learning studies, in addition to face perception methodologies overall. Put simply, I suggest that in order to understand face identification processes comprehensively, it is important to consider both between- and within-person variability.

Face recognition is widely held to rely on 'configural processing', recently defined as an analysis of metric distances between features. Given that face recognition concerns those faces of people who we know, it is suggested that our unique representations of familiar faces contain information about these metric distances. The experiments in this thesis examine the hypothesis that face recognition relies on 'configural processing' by comparing performance between familiar and unfamiliar faces in a range of tasks. Experiments in the first half of the thesis investigate the effects of geometric distortions on different face tasks. Experiments in the second half examine familiarity advantages in rescaling distorted facial images. The main findings are that face recognition might not rely on simple measures of metric distances between features, and that observers show a surprising degree of tolerance to configural changes applied to familiar faces. This suggests that an operationalisation of configural processing will need to consider other measures that do not survive the image deformations tested in this thesis. The findings are discussed in relation to existing research on familiar face recognition as distinct from unfamiliar face perception.

The present research addressed an assumption of Attention Restoration Theory (ART), which predicts that built scene content captures attention more strongly than natural content. Section І covers the findings of three pilot studies that were aimed at finding a suitable methodology for contrasting the saliency of natural and built content. An initial study in which use was made of a Rapid Serial Visual Presentation (RSVP) did not provide evidence for divergent saliency levels between natural and built scene categories. Hence, a Go/No-Go paradigm with shorter exposure times was used in later studies. A second pilot study was carried out in order to determine which scene category labels are both comprehensible and interpreted consistently across respondents. A third pilot study was aimed at filtering out boundary case scenes from the set of images pre-selected by the experimenter. Section ІІ covers four studies, which addressed two aims: (1) To test whether built content is more salient than natural scene content, and (2) to test the effect of inconsistent built and natural elements on saliency. These studies supported the claim of ART that built scenes are more salient than natural scenes. In addition, they provided evidence for the assumption that a built element increases the saliency of a natural scene more strongly than a natural element increases the saliency of a built scene. The relationship between saliency of content and restoration is explored in Section ІІІ. The findings provided mixed evidence in support of ART. Restoration of alerting attention was more complete following non-salient than salient scenes. However, previous research indicating stronger restoration of executive attention and working memory span in response to natural than built content exposures was not replicated. Furthermore, restoration of orienting attention was more complete following salient than non-salient scene presentations. It is concluded that saliency of scene content is predictive of psychological restoration, albeit not necessarily in the way as predicted by ART.

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The purpose  of this essay is to see how  important  the cover of the  book  is for the  child, when it makes its choice of which book to read. I will also try to explain the process of seeing and perception, which includes interpretation of what you are seeing and, further on, gestalt psychology. Through gestalt psychology you can interpret what is showing in a picture, and your way of interpretation depends on earlier experiences in seeing pictures. What is also important in the interpretation is the social role in which every person act, and this role is different for every person. The way you interpret is the same, man as well as woman, but what solution you choose to believe in variates from person to person. A  questionnaire ,vas given to  I07 children  at the age between  9-12 years. They were asked about their  reading-habits  and  were shown  16 covers from  books for children  at their  age. They were asked  to pick  out the two covers they  liked  best  and  write down why  they  had chosen them. The result shows, that the cover of the book  is not that  important to the child, instead  it is the text of the back of the book that  is the most  important thing when  the child choses its book.

published_or_final_version / Industrial and Manufacturing Systems Engineering / Doctoral / Doctor of Philosophy

published_or_final_version / Psychology / Doctoral / Doctor of Philosophy

published_or_final_version / Philosophy / Master / Master of Philosophy