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Visual perception

Friday, September 30th,   2011 [17:20 - 19:20]

PS_1.005 - Esthetics ratings differ drastically from balance ratings and physical equilibrium ratings

Samuel, F. & Kerzel, D.

FPSE. Université de Genève. Geneva, Switzerland

In a three-part experiment we presented compositions with two black rectangles on a white surface in order to investigate which stimulus variables influence esthetics ratings, balance ratings, and physical equilibrium ratings. The three questions for the ratings where: Is the composition nice? Are the black rectangles distributed in a balanced way in the white surface? On which side and to what extent is there more “weight” on one side of the composition? The systematic variation of the stimuli allowed us to see clear differences between the three ratings: We found that a large difference between the sizes of the two rectangles influenced the perceived esthetic value positively, while it influenced the perceived balance value negatively. We also observed that the balance ratings correlated only for a few participants with the positions of the center of mass of the two black surfaces, but for all participants the physical equilibrium ratings correlated very much with the positions of the center of mass. Our findings highlight that esthetic judgments should not be considered equivalent to balance judgments and only for a few people does balance correspond to physical equilibrium.

PS_1.006 - How to analyse eye-movements patterns in moving images environments? The example of car driving

Navarro, J.

University of Lyon II

Eye-tracking devices are now very common in almost all cognitive psychology research fields. These devices have initially been designed to record and analyse gaze position on still images. Gaze position recordings are therefore perfectly adapted for cognitive activities such as reading. However, cognitive activities on moving images are also of interest. For instance, a large community in the cognitive ergonomics field is working on car driving, involving moving images situations. Eye-trackers manufacturers have developed softwares to analyse the eye data recorded, but those softwares are not adapted to moving images situations. Indeed these softwares analyse gaze directions using the moving images display as system of reference and not the images themselves. The present presentation will focus on quantitative and objective analysis of gaze position data collected on moving images environments. The different methods currently used in the car driving area will be presented and discussed according to their advantages and drawbacks. Then, what happened to be the most appropriate method, according to the comparison of the different methods presented, will be proposed as a standard method

PS_1.007 - Rapidly presented letters, faces, shapes: On the left visual-field advantage in RSVP task

Asanowicz, D. 1 , ƚmigasiewicz, K. 2 & Verleger, R. . 2

1 Institute of Psychology, Jagiellonian University, Krakow, Poland
2 Department of Neurology, University of Lübeck, Lübeck, Germany

In the dual rapid serial visual presentation task, two simultaneous different streams of letters with two targets (T1 & T2) embedded among distractors are rapidly presented in the left and right visual fields. Importantly, T2 is identified markedly better in the left than in the right visual field. In a series of experiments we tested two alternative explanations of the left visual field advantage (LVFA). According to the first one, the LVFA may reflect right hemisphere (RH) dominance in attentional processes. Alternatively, the asymmetry may be caused by left hemisphere (LH) disadvantage, since the LH may be overloaded by rapidly presented letters due to its specialization in processing verbal stimuli. In the first three experiments we gradually reduced distracting stimuli in order to decrease the postulated LH overload. In the next two experiments we employed stimuli for which the RH is specialized, human faces (exp.4) and shapes (exp.5). The LVFA remained consistently present across all experiments, despite the manipulations in procedure and the variation of stimuli. Therefore, the studies seem to falsify the hypothesis of LH overload, and instead suggest that RH superiority, possibly in attentional processing, underlies the LVFA in the dual RSVP task.

PS_1.008 - Measuring the timing of letter identification processes

Madec, S. 1, 2 , Arnaud, R. 1, 2 & Jonathan, G. 1, 2

1 CNRS, France
2 Laboratoire de Psychologie Cognitive, Aix-Marseille University, Marseille, France

How long does it take to identify a simple visual symbol like a letter? We address this general issue by measuring letter identification times for five participants (1) in a naming/delayed naming task and (2) in a perceptual identification task. To obtain an index of letter identification times from the first task, we subtract delayed naming times (indexing voice-key constraints and output processes) from naming times. We found that the resulting mean letter identification times were strongly correlated between participants and within each task. However, the correlation between mean response times per letter across tasks were surprisingly quite low (r[24] = .24) and while letter frequency was correlated with the first task (r[24]=-.49), this was not the case for the second task (r[24]=.07). These results suggest that different task-dependent cognitive processes are involved in each of these experimental paradigms and that there are no task-independent ways of measuring identification times. Simulations done with a simple interactive activation model of letter processing indicate that, in the naming/delayed naming task, lateral inhibition connections at the letter level plays a major role while feedback connections are more important in the perceptual identification task.

PS_1.009 - Measuring experimental software timing errors in the presentation of visual stimuli

Garaizar, P. 1, 2 , Vadillo, M. A. 3 & Matute, H. 3

1 Departamento de Telecomunicaciones. Universidad de Deusto. Bilbao, Spain.
2 DeustoTech. Universidad de Deusto. Bilbao, Spain.
3 Departamento de Fundamentos y Métodos de la Psicología. Universidad de Deusto. Bilbao, Spain.

Nowadays psychology researchers have a wide range of experimental software alternatives to meet their visual stimuli presentation needs. Nevertheless, most of these tools have to deal with two main issues: most devices used for the presentation of the stimuli have low refresh rate (typically at 60-85 Hz) and the most widely used platforms (e.g. Microsoft Windows on a PC) are not real-time systems. This study analyses the discrepancies between the experimental timing conditions defined by the researcher when using specialized software and the actual onset and offset times of the visual stimuli detected through the Black Box Toolkit photosensors. As expected, the accuracy of timing was found to be affected not only by the experimental software itself but also by the presentation devices and the underlying platform responsiveness.

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