Identification of Everyday Objects on the Basis of Gaborized Outline Versions

Abstract

Using outlines derived from a widely used set of line drawings, we created stimuli geared towards the investigation of contour integration and texture segmentation using shapes of everyday objects. Each stimulus consisted of Gabor elements positioned and oriented curvilinearly along the outline of an object, embedded within a larger Gabor array of homogeneous density. We created six versions of the resulting Gaborized outline stimuli by varying the orientations of elements inside and outside the outline. Data from two experiments, in which participants attempted to identify the objects in the stimuli, provide norms for identifiability and name agreement, and show differences in identifiability between stimulus versions. While there was substantial variability between the individual objects in our stimulus set, further analyses suggest a number of stimulus properties which are generally predictive of identification performance. The stimuli and the accompanying normative data, both available on our website (http://www.gestaltrevision.be/sources/gaboroutlines), provide a useful tool to further investigate contour integration and texture segmentation in both normal and clinical populations, especially when top-down influences on these processes, such as the role of prior knowledge of familiar objects, are of main interest.

Peripheral Contour Grouping and Saccade Targeting: The Role of Mirror Symmetry

“…Deviations in landing position were also smaller for contours with smaller inter-element angles, which are known to be easier to integrate [21,46,47]. This supports an interpretation of the symmetry effect in terms of grouping and not (only) saccade targeting per se.…”

“…Compared to natural scenes, contour integration stimuli are inherently cluttered as a result of the placement of many distracter elements to eliminate proximity or density cues, which is a necessary and general limitation of this paradigm that was designed to isolate grouping by good continuation. Although earlier research has shown that participants can reliably identify many everyday object shapes embedded in such Gabor stimuli when presented in central vision [46,47], it is arguably unclear how accurate or detailed participants' perception of contour shape was with our eccentrically presented shapes, and whether participants perceived the complete closed contour.…”

“…Saccadic latency did seem to properly reflect the speed or difficulty of contour integration in the sense that log latency was proportional to the contours' mean path angle in all three experiments, and contour detection difficulty is known to increase with inter-element angle (e.g., [21]; see also [46,47]). However, any influence of symmetry on saccadic latency was simply absent or at least not strong enough to show up in the results.…”

“…There is evidence that symmetry serves as a cue in classical figure-ground tasks [17,[53][54][55][56], but local shape characteristics such as the path angle [21,46,47], and global characteristics such as convexity [58] or familiarity [59] seem to be more important determinants of performance in contour integration tasks. Contour integration benefits only slightly from global symmetry in central vision [18], and the benefit is apparently further reduced or entirely absent in peripheral vision.…”

The construction of perceptual grouping displays using GERT

“…These grouping stimuli come in many flavors: textured regions (e.g., Giora & Casco, 2007;Harrison & Feldman, 2009;Julesz, 1981;Lamme, 1995;Nothdurft, 1985;Roelfsema, Lamme, Spekreijse, & Bosch, 2002;Rossi, Desimone, & Ungerleider, 2001;Wolfson & Landy, 1998), oriented line fields (e.g., Li & Gilbert, 2002;Tversky, Geisler, & Perry, 2004), Gabor fields (e.g., Dakin & Baruch, 2009;Demeyer, De Graef, Verfaillie, & Wagemans, 2011;Field, Hayes, & Hess, 1993;Kovács & Julesz, 1993;Machilsen, Pauwels, & Wagemans, 2009;Nygård, Van Looy, & Wagemans, 2009;Persike & Meinhardt, 2008;Sassi, Vancleef, Machilsen, Panis, & Wagemans, 2010;Watt, Ledgeway, & Dakin, 2008), dot lattices (e.g., Bleumers, De Graef, Verfaillie, & Wagemans, 2008;Claessens & Wagemans, 2005Kubovy & Wagemans, 1995;Põder, 2011), Glass patterns (e.g., Khuu, Moreland, & Phu, 2011;Palomares, Pettet, Vildavski, Hou, & Norcia, 2010;, and many more.…”