Minimal information to determine affine shape equivalence.

Abstract

Participants judged the affine equivalence of 2 simultaneously presented 4-point patterns. Performance level (d') varied between 1.5 and 2.7, depending on the information available for solving the correspondence problem (insufficient in Experiment 1a, superfluous in Experiment 1b, and minimal in Experiments 1c, 2a, 2b) and on the exposure time (unlimited in Experiments 1 and 2a and 500 ms in Experiment 2b), but it did not vary much with the complexity of the affine transformation (rotation and slant in Experiment 1 and same plus tilt in Experiment 2). Performance in Experiment 3 was lower with 3-point patterns than with 4-point patterns, whereas blocking the trials according to the affine transformation parameters had little effect. Determining affine shape equivalence with minimal-information displays is based on a fast assessment of qualitatively or quasi-invariant properties such as convexity/ concavity, parallelism, and collinearity.

Formation of visual “objects” in the early computation of spatial relations

“…Nonaccidental properties do induce grouping, but only with some caveats: collinearity induces grouping only in the more general guise of relatability and Gestalt good continuation, and cotermination induces grouping only when the angle is small, again consistent with good continuation. Symmetry, by its nature a less local and more configural cue, induces grouping even after short processing times, reflecting its importance in the early computation of pattern structure (Kukkonen, Foster, Wood, Wagemans, & van Gool, 1996;Wagemans, 1997;Wagemans, van Gool, Lamote, & Foster, 2000). The interplay of cues across time is revealed particularly vividly by the data for T-junctions, which suggest that local cues dominate early while configural cues eventually override them.…”

Mental rotation versus invariant features in object perception from different viewpoints: an fMRI study

“…Again, this process is not the most typical for everyday object recognition, but the operation of detecting and exploiting image invariances is clearly an important and relevant topic (e.g. [53]). Moreover, in the present experiment, top-down influences are likely to come into play, because the observers know what kind of feature is crucial to solve the task.…”

Évaluer la diversité dans des ensembles d’objets en faisant référence aux transformations comme critères

“…Experiments of this kind have actually been performed in studying "perceptual shape equivalence" (e.g. [Niall, Macnamara, 1990;Wagemans, 1993;Wagemans, van Gool, Lamote, Foster, 2000]). The net result of such an experiment (when run on one participant) would be a subset A of X, i.e., the set of comparison stimuli y that received the response "same" when compared with the standard stimulus x.…”