Cue validity and object-based attention

In a previous study, Egly, Driver, and Rafal (1994) observed both space- and object-based components of visual selective attention. However, the mechanisms underlying these two components and the relationship between them are not well understood. In the present research, with a similar paradigm, these issues were addressed by manipulating cue validity. Behavioral results indicated the presence of both space- and object-based components under high cue validity, similar to the results of Egly et al.'s study. In addition, under low cue validity, the space-based component was absent, whereas the object-based component was maintained. Further event-related potential results demonstrated an object-based effect at a sensory level over the posterior areas of brain, and a space-based effect over the anterior region. The present data suggest that the space- and object-based components reflect mainly voluntary and reflexive mechanisms, respectively

Artificially created stimuli produced by a genetic algorithm using a saliency model as its fitness function show that Inattentional Blindness modulates performance in a pop-out visual search paradigm

Salient stimuli are more readily detected than less salient stimuli, and individual differences in such detection may be relevant to why some people fail to notice an unexpected stimulus that appears in their visual field whereas others do notice it. This failure to notice unexpected stimuli is termed 'Inattentional Blindness' and is more likely to occur when we are engaged in a resource-consuming task. A genetic algorithm is described in which artificial stimuli are created using a saliency model as its fitness function. These generated stimuli, which vary in their saliency level, are used in two studies that implement a pop-out visual search task to evaluate the power of the model to discriminate the performance of people who were and were not Inattentionally Blind (IB). In one study the number of orientational filters in the model was increased to check if discriminatory power and the saliency estimation for low-level images could be improved. Results show that the performance of the model does improve when additional filters are included, leading to the conclusion that low-level images may require a higher number of orientational filters for the model to better predict participants' performance. In both studies we found that given the same target patch image (i.e. same saliency value) IB individuals take longer to identify a target compared to non-IB individuals. This suggests that IB individuals require a higher level of saliency for low-level visual features in order to identify target patches

Change blindness: eradication of gestalt strategies

Arrays of eight, texture-defined rectangles were used as stimuli in a one-shot change blindness (CB) task where there was a 50% chance that one rectangle would change orientation between two successive presentations separated by an interval. CB was eliminated by cueing the target rectangle in the first stimulus, reduced by cueing in the interval and unaffected by cueing in the second presentation. This supports the idea that a representation was formed that persisted through the interval before being 'overwritten' by the second presentation (Landman et al, 2003 Vision Research 43149–164]. Another possibility is that participants used some kind of grouping or Gestalt strategy. To test this we changed the spatial position of the rectangles in the second presentation by shifting them along imaginary spokes (by ±1 degree) emanating from the central fixation point. There was no significant difference seen in performance between this and the standard task [F(1,4)=2.565, p=0.185]. This may suggest two things: (i) Gestalt grouping is not used as a strategy in these tasks, and (ii) it gives further weight to the argument that objects may be stored and retrieved from a pre-attentional store during this task

Engineering data compendium. Human perception and performance. User's guide

The concept underlying the Engineering Data Compendium was the product of a research and development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design and military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from the existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by systems designers. The present four volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is the first volume, the User's Guide, containing a description of the program and instructions for its use

Preserved local but disrupted contextual figure-ground influences in an individual with abnormal function of intermediate visual areas

Visual perception depends not only on local stimulus features but also on their relationship to the surrounding stimulus context, as evident in both local and contextual influences on figure-ground segmentation. Intermediate visual areas may play a role in such contextual influences, as we tested here by examining LG, a rare case of developmental visual agnosia. LG has no evident abnormality of brain structure and functional neuroimaging showed relatively normal V1 function, but his intermediate visual areas (V2/V3) function abnormally. We found that contextual influences on figure-ground organization were selectively disrupted in LG, while local sources of figure-ground influences were preserved. Effects of object knowledge and familiarity on figure-ground organization were also significantly diminished. Our results suggest that the mechanisms mediating contextual and familiarity influences on figure-ground organization are dissociable from those mediating local influences on figure-ground assignment. The disruption of contextual processing in intermediate visual areas may play a role in the substantial object recognition difficulties experienced by LG

Cognitivism and Innovation in Economics - Two Lectures

This issue of the Department W.P. reproduces two lectures by Professor Loasby organized by the CISEPS (Centre for Interdisciplinary Studies in Economics, Psychology and the Social Sciences at Bicocca) in collaboration with the IEP, the Istituto di Economia Politica of the Bocconi University in Milan. The first lecture was delivered at the University of Milano-Bicocca on 13 October 2003 and the second was staged the day after at the Bocconi University. The lectures are reproduced here together with a comment by dr. Stefano Brusoni of Bocconi and SPRU. Two further comments were presented at the time by Professor Richard Arena of the University of Nice and by Professor Pier Luigi Sacco of the University of Venice. Both of them deserve gratitude for active participation to the initiative. Unfortunately it has not been possible to include their comments in the printed form. In these lectures Brian Loasby opens under the title of Psychology of Wealth (a title echoing a famous essay by Carlo Cattaneo) and he develops an argument in cognitive economics which is based on Hayek’s theory of the human mind with significant complements and extensions, mainly from Smith and Marshall. The second lecture provides a discussion on organization and the human mind. It can be read independently although it is linked to the former. Indeed, in Professor Loasby’s words, “the psychology of wealth leads to a particular perspective on this problem of organization”. The gist of the argument lies in the need to appreciate the significance of an appropriate “balance between apparently conflicting principles: the coherence, and therefore the effectiveness, of this differentiated system requires some degree of compatibility between its elements, but the creation of differentiated knowledge and skills depends on the freedom to make idiosyncratic patterns by thinking and acting in ways which may be radically different from those of many other people”. This dilemma of compatibility vs. independence can find solution in a variety of contexts, as Loasby’s analysis shows. In his comments Richard Arena had focussed on the rationality issues, so prominent in Loasby’s text. For example, he had suggested that the cleavage between rational choice equilibrium and evolutionary order offers ground to new forms of self-organization. Pier Luigi Sacco had emphasized that Loasby’s approach breaks new ground on the economics of culture and paves the way to less simplistic conceptions of endogenous growth than is suggested by the conventional wisdom of current models. Unfortunately, as hinted above, is has proved impossible to include those comments in the present booklet along with Loasby’s lectures. A special obligation must be recorded to Dr. Stefano Brusoni, who has prepared a written version of his own comment which has been printed in this booklet and can be offered to the reader. Among other participants Roberto Scazzieri, of the University of Bologna, Tiziano Raffaelli, of the University of Pisa, Luigino Bruni of Bicocca, Riccardo Cappellin of Rome ‘Tor Vergata’ and others were able to offer significant comments during the two sessions of the initiative. The organizers are particularly grateful to Professor Brian Loasby for the active and generous support of the initiative. Together with our colleagues and students we have been able to admire his enthusiasm and intellectual creativity in treating some of the more fascinating topics of contemporary economics.

Evaluating achievement on mathematics and science problems: The role of global and local processing

This thesis sought to clarify relationships between whole-part constructs; where responses are thought to reflect a focus on the whole stimulus or context, or on individual elements (the parts). Children aged 5 to 10 years completed a number of tasks allowing developmental changes to be measured on a cross-sectional and longitudinal basis. Global and local processing tasks (Navon tasks: free choice, selective attention, and divided attention) revealed a change in response patterns between the ages of 6 and 7 years, the precise nature of which varied depending on the attentional demands of the task. Field independence tasks (Children’s Embedded Figures Test (CEFT) and Design Organisation Test (DOT)) revealed that children became more field independent with increasing age. A parental questionnaire measuring systemizing (the analysis or construction of a rule-based system) was administered at a single timepoint and revealed no cross-sectional age-related changes. Behavioural tasks and eye-tracking technology were employed to understand possible mechanisms underlying field independence performance. Visuospatial IQ and working memory explained variation on both field independence tasks. Higher accuracy on the CEFT reflected fewer and shorter fixations on distractor areas as well as longer and more fixations on target areas. Better response inhibitory control related to higher disembedding accuracy, while better semantic inhibitory control related to fewer and shorter fixations on distractor areas. Together, these explain how domain-general factors contribute to performance on the CEFT. The second part of this thesis examined associations between whole-part constructs and mathematics and science achievement. Global and local processing and systemizing revealed few significant associations with the academic scores. Better field independence was associated with higher scores on both mathematics and science. After controlling for age and domain-general factors, the field independence tasks explained additional variance on specific mathematics and science tests, which likely reflect common processes involved in the tasks