Based on ten experiments, this thesis examines representational neglect in brain damaged patients and in matched controls.  The patients sometimes show a specific deficit in visual imaging:  neglected one half of their mental representations.  Although several studies addressed the issue of visuo-perceptual neglect, the representational defect is underinvestigated.  Only a few standardized tests are available for its detention and assessment, and therefore rarely it is diagnosed in clinical practise or investigated in experimental work.  In this thesis some new tests to investigate representational neglect are proposed.  Moreover, representational neglect is evaluated in different sensory modalities (visual, tactile as well as within the personal domain) to address the issue of supramodality or plurimodality of this deficit.

The thesis investigates the <i>unconscious transference</i> phenomenon which has been implicated in cases of mistaken identity. When an eyewitness to a crime misidentifies an innocent, but previously encountered person as the perpetrator in response to a lineup which does not include culprit, it has been speculated that the eyewitness confuses the two people by <i>transferring </i>their identities across contexts. This traditional definition of unconscious transference was investigated in one of two experiments. A videotaped, staged theft scenario was shown to 770 participant witnesses who attempted to identify the perpetrator from a photographic lineup. Those who viewed an innocent bystander prior to the crime scenario, were more likely to mistake that familiar person for the perpetrator when the latter was absent from the lineup, compared to control participants who were not shown the bystander. Bystander misidentifications obtained indicate that transference did occur. A significant minority of participants consciously inferred that the bystander and the perpetrator were the same person seen in different settings. Others realised that the two confederates were different individuals but misattributed the source of their memories. In a second experiment, evidence of another type of unconscious transference, characterised as a <i>commitment effect, </i>was obtained. Three months after the initial lineup, a second lineup administered to 505 participants from the first investigation indicated that an innocent person initially misidentified is likely to continue to be misidentified even if he/she was unfamiliar to the eyewitness prior to his photograph being shown. Further, a repeat misidentification is likely even when the perpetrator is included in the subsequent lineup. Cognitive mechanisms implicated in the transference effects include some monitoring and memory blending. However, relative judgements, demand characteristics and changes of presentation media were also implicated. The ramifications for forensic eyewitness situations are such that unconscious transference demands increased attention from eyewitness researchers.

No description available.

This thesis examines how the objects that we visually perceive in the world are coupled to the actions that we make towards them. For example, a whole hand grasp might be coupled with an object like an apple, but not with an object like a pea. It has been claimed that the coupling of what we see and what we do is not simply associative, but is fundamental to the way the brain represents visual objects. More than association, it is thought that when an object is seen (even if there is no intention to interact with it), there is a partial and automatic activation of the networks in the brain that plan actions (such as reaches and grasps). The central aim of this thesis was to investigate how specific these partial action plans might be, and how specific the properties of objects that automatically activate them might be. In acknowledging that perception and action are dynamically intertwining processes (such that in catching a butterfly the eye and the hand cooperate with a fluid and seamless efficiency), it was supposed that these couplings of perception and action in the brain might be loosely constrained. That is, they should not be rigidly prescribed (such that a highly specific action is always and only coupled with a specific object property) but they should instead involve fairly general components of actions that can adapt to different situations. The experimental work examined the automatic coupling of simplistic left and right actions (e.g. key presses) to pictures of oriented objects. Typically a picture of an object was shown and the viewer responded as fast as possible to some object property that was not associated with action (such as its colour). Of interest was how the performance of these left or right responses related to the task irrelevant left or right orientation of the object. The coupling of a particular response to a particular orientation could be demonstrated by the response performance (speed and accuracy). The more tightly coupled a response was to a particular object orientation, the faster and more accurate it was. The results supported the idea of loosely constrained action plans. Thus it appeared that a range of different actions (even foot responses) could be coupled with an object's orientation. These actions were coupled by default to an object's X-Z orientation (e.g. orientation in the depth plane). In further reflecting a loosely constrained perception-action mechanism, these couplings were shown to change in different situations (e.g. when the object moved towards the viewer, or when a key press made the object move in a predictable way). It was concluded that the kinds of components of actions that are automatically activated when viewing an object are not very detailed or fixed, but are initially quite general and can change and become more specific when circumstances demand it.

No description available.

The incorporation of the sense of touch into virtual reality is an exciting development. However, research into this topic is in its infancy. This experimental programme investigated both the perception of virtual object attributes by touch and the parameters that influence touch perception in virtual reality with a force feedback device called the PHANTOM (TM) (www.sensable.com). The thesis had three main foci. Firstly, it aimed to provide an experimental account of the perception of the attributes of roughness, size and angular extent by touch via the PHANTOM (TM) device. Secondly, it aimed to contribute to the resolution of a number of other issues important in developing an understanding of the parameters that exert an influence on touch in virtual reality. Finally, it aimed to compare touch in virtual reality between sighted and blind individuals. This thesis comprises six experiments. Experiment one examined the perception of the roughness of virtual textures with the PHANTOM (TM) device. The effect of the following factors was addressed: the groove width of the textured stimuli; the endpoint used (stylus or thimble) with the PHANTOM (TM); the specific device used (PHANTOM (TM) vs. IE3000) and the visual status (sighted or blind) of the participants. Experiment two extended the findings of experiment one by addressing the impact of an exploration related factor on perceived roughness, that of the contact force an individual applies to a virtual texture. The interaction between this variable and the factors of groove width, endpoint, and visual status was also addressed. Experiment three examined the perception of the size and angular extent of virtual 3-D objects via the PHANTOM (TM). With respect to the perception of virtual object size, the effect of the following factors was addressed: the size of the object (2.7,3.6,4.5 cm); the type of virtual object (cube vs. sphere); the mode in which the virtual objects were presented; the endpoint used with the PHANTOM (TM) and the visual status of the participants. With respect to the perception of virtual object angular extent, the effect of the following factors was addressed: the angular extent of the object (18,41 and 64°); the endpoint used with the PHANTOM (TM) and the visual status of the participants. Experiment four examined the perception of the size and angular extent of real counterparts to the virtual 3-D objects used in experiment three. Experiment four manipulated the conditions under which participants examined the real objects. Participants were asked to give judgements of object size and angular extent via the deactivated PHANTOM (TM), a stylus probe, a bare index finger and without any constraints on their exploration. In addition to the above exploration type factor, experiment four examined the impact of the same factors on perceived size and angular extent in the real world as had been examined in virtual reality. Experiments five and six examined the consistency of the perception of linear extent across the 3-D axes in virtual space. Both experiments manipulated the following factors: Line extent (2.7,3.6 and 4.5cm); line dimension (x, y and z axis); movement type (active vs. passive movement) and visual status. Experiment six additionally manipulated the direction of movement within the 3-D axes. Perceived roughness was assessed by the method of magnitude estimation. The perceived size and angular extent of the various virtual stimuli and their real counterparts was assessed by the method of magnitude reproduction. This technique was also used to assess perceived extent across the 3-D axes. Touch perception via the PHANTOM (TM) was found to be broadly similar for sighted and blind participants. Touch perception in virtual reality was also found to be broadly similar between two different 3-D force feedback devices (the PHANTOM (TM) and the IE3000). However, the endpoint used with the PHANTOM (TM) device was found to exert significant, but inconsistent effects on the perception of virtual object attributes. Touch perception with the PHANTOM (TM) across the 3-D axes was found to be anisotropic in a similar way to the real world, with the illusion that radial extents were perceived as longer than equivalent tangential extents. The perception of 3-D object size and angular extent was found to be comparable between virtual reality and the real world, particularly under conditions where the participants' exploration of the real objects was constrained to a single point of contact. An intriguing touch illusion, whereby virtual objects explored from the inside were perceived to be larger than the same objects perceived from the outside was found to occur widely in virtual reality, in addition to the real world. This thesis contributes to knowledge of touch perception in virtual reality. The findings have interesting implications for theories of touch perception, both virtual and real.

No description available.

Emotional expression has been intensively researched in the past, however, this research was normally conducted on facial expressions and only seldomly on dynamic stimuli. We have been interested in better understanding the perception and cognition of emotion from human motion. To this end 11 experiments were conducted that spanned the perception and representation of emotion, the role spatial and temporal cues played in the perception of emotions and finally high level cognitive features in the categorisation of emotion. The stimuli we employed were point-light displays of human arm movements recorded as actors portrayed ordinary actions with emotion. To create them we used motion capture technology and computer animation techniques. Results from the first two experiments showed basic human competence in recognition of emotion and that the representation of emotions is along two dimensions. These dimensions resembled arousal and valence, and the psychological space resembled that found for both facial expression and experienced affect. In a search for possible stimulus properties that would act as correlates for the dimensions, it emerged that arousal could be accounted for by movement speed while valence was related to phase relations between joints in the displays. In the third experiment we manipulated the dimension of arousal and showed that through a modulation of duration, perception of angry, sad and neutral movements could be modulated. In experiments 4-7 the contribution of spatial cues to the perception of emotion was explored and in the final set of experiments (8-11) perception of emotion was examined from a cognitive perspective. Through the course of the research a number of interesting findings emerged that suggested three primary directions for future research: the possible relationship between attributions of animacy and emotion to animate and inanimate non-humans. The phase or timing relationships between elements in a display as a categorical cue to valence and finally the unexplored relationship between cues to emotion from movements and faces.

Glogower et al. (1978) have suggested that coping self-statements (CSS) form the major therapeutic component of cognitive restructuring therapies. However, to date there has been no consensus in the literature about the nature of effective CSS. Indeed, many studies which have examined the effects of cognitive therapies have failed to adequately describe the CSS component of the therapies. The initial focus of this thesis was on two coping strategies which have been described (Meichenbaum, 1971; Evans, 1977). Both strategies encourage fearful subjects to cope with the physiological concomitants of fear on the assumption that fear is mediated by their perceptions of such concomitants. However, the emphasis of these strategies is quite different; Evans' strategy encourages subjects to passively accept the physiological concomitants of fear (PCS) while Meichenbaum's encourages subjects to actively cope with this aspect of fear by self-instructing to relax and keep calm (ACS). It was found that the former strategy (PCS) had a beneficial effect upon fear of spiders but lead to an increase in fear for a group of speech-anxious subjects. The ACS had a significant fear-reducing effect upon speech anxiety. In addition, it was found that fearful public speakers who devised their own strategies experienced a reduction in fear. The possible interpretation of these findings prompted an investigation of the relationship between locus of control orientation and the expression of fear. It was found that externality was positively correlated with fear of many of the items on the FSS III (Wolpe, 1973) including the item 'Speaking in Public'. However, when actually presenting a speech it was found that fearful internals expressed significantly more fear than fearful externals. Interpretations of this finding are discussed along with possible implications for therapy. A practically convenient procedure for investigating speech anxiety is described. An investigation of the recognition of the non-verbal expression of speech anxiety is also reported.

It has often been argued that the processing of faces is 'special' relative to the processing of other objects and there is much evidence in support of this notion. One source of evidence is the inversion effect, which occurs when faces presented upright are recognised significantly better than faces presented upside down. This effect of stimulus inversion has been shown to impair face recognition to a greater extent than for any other object class. It is this disproportionate effect that has been given as one source of evidence that face processing is special. However, other research has argued that effects of inversion can be found for non-face stimuli providing that there is sufficient development of expertise with them and that these stimuli can be defined by a common prototype. This thesis further explores this idea. Inversion effects were investigated for both prototypically and non-prototypically defined, abstract, chequerboard stimuli and compared with those for faces. When subjects learned to categorise chequerboard stimuli that were defined by a common prototype equal size inversion effects were found to those observed for faces. However, inversion effects were not observed for category training with multiple exemplars of chequerboard stimuli that were not defined by a common prototype. Together the findings are consistent with the idea that inversion effects are a general phenomenon resulting from the acquisition of category expertise with any prototype defined stimulus category. They undermine the inversion effect as a source of evidence for the specialness of face processing. Further, using a new Moving Windows technique, additional experiments investigated the underlying mechanisms responsible for the effects of inversion found for faces and chequerboards. These showed that the diagnostic image regions searched differ across the two stimulus classes. However, on the basis of the results, it is argued that the inversion effects found for both could result from impaired processing of second-order configural information.