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OS_21. Object recognition & Visual processing

Saturday, October 01st,   2011 [10:50 - 11:50]


OS_21.1 - Expectation and priming affect pop-out target visibility

Pascucci, D. , Mastropasqua, T. & Turatto, M.

Department of Cognitive Sciences and Education, Rovereto, Italy

In visual perception, the exposition to a visual target enhances the processing of the same target on a future encounter (Schacter, 1998). The priming of pop out (Maljkovic & Nakayama, 1994) provides an example of this perceptual facilitation, in which the repetition of the same target-distractors colour configuration, increases the speed with which target is discriminated. However, little is known as to whether priming of pop-out also improves target visibility. The aim of the present study is to evaluate whether the repetition of the singleton target color can change its visibility, which was manipulated via metacontrast masking. To this aim the color of the target was either kept constant (blocked condition) or changed randomly (random condition). Results showed that subjects were better at identifying the target in the blocked as compared to the random condition. This suggests a possible interaction between memory and attention-perception mechanisms. Interestingly, however, when repetitions of the same color in the random condition are considered, target visibility increased for runs up to 3, but then decreased for longer runs. We hypothesize that this could reflect mechanisms of “switch expectation” that interfere with the visual short memory system.

OS_21.2 - What does our gaze behaviour tell us about how we categorize an object?

Hartendorp, M. , Van der Stigchel, S. , Hooge, I. & Postma, A.

Experimental Psychology, Helmholtz Institute, Utrecht University, Utrecht, The Netherlands

Our gaze behaviour can inform us which information we use from the visual input to categorize an object. For instance, when we perceive a living object, we prefer to look at the head of the animal. In the current study, we used morphed figures to investigate whether the interpretation pattern of these unclear objects is reflected in the eye-movement pattern. Morphed figures are created by slowly changing one object into another object. For example, a morphed figure can consist for 70% of object A (dominant object) and for 30% of object B (nondominant object). We conducted a free-naming experiment in which the eye-movements were recorded simultaneously. We investigated whether a similar eye-movement pattern was registered for morphed figures that were categorized as the same object. Our data suggest a strong correlation between what we see in a morphed figure and where we look at in a morphed figure. The next step is to reveal the direction of this correlation: can we predict the eye-movement pattern on the basis of the interpretation or can we predict the interpretation on the basis of the eye-movement pattern?

OS_21.3 - Interhemispheric transfer costs in word reading: Evidence for a split fovea

Van der Haegen, L. & Brysbaert, M.

Ghent University

The split fovea theory (SFT) states that centrally and parafoveally presented information is organized in the same way: Letters at the left/right side of fixation are initially sent to the right/left hemisphere respectively. As a consequence, the beginning of a word is the optimal viewing position for readers with left hemispheric language dominance because this makes most letters of a word fall into the right visual field. Until now, the assumptions of SFT were never directly tested under strict methodological settings such as stimulus sizes within the central 3° of vision and strict fixation control. In the present study, subjects with typical left and atypical right language dominance named three-, four- and six-letter words at different fixation locations. An eye-tracking device controlled the fixation position of both eyes and registered naming latencies for all possible letter position fixations. Results showed that left dominant subjects were fastest when fixating at the word beginning whereas the optimal viewing position of right dominant subjects was situated more towards the end of the word. Consequently, visual word recognition models should take into account that interhemispheric transfer is needed for both parafoveal and foveal word recognition.

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