Grouping in object recognition: The role of a Gestalt law in letter identification

Abstract

The Gestalt psychologists reported a set of laws describing how vision groups elements to recognize objects. The Gestalt laws “prescribe for us what we are to recognize ‘as one thing’.” (Köhler, 1920). Were they right? Does object recognition involve grouping? Tests of the laws of grouping have been favorable, but mostly assessed only detection, not identification, of the compound object. The grouping of elements seen in the detection experiments with lattices and ‘snakes in the grass’ is compelling, but falls far short of the vivid everyday experience of recognizing a familiar, meaningful, named thing, which mediates the ordinary identification of an object. Thus, after nearly a century, there is hardly any evidence that grouping plays a role in ordinary object recognition. To assess grouping in object recognition, we made letters out of grating patches and measured threshold contrast for identifying these letters in visual noise as a function of perturbation of grating orientation, phase, and offset. We define a new measure, “wiggle,” to characterize the degree to which these various perturbations violate the Gestalt law of good continuation. We find that efficiency for letter identification is inversely proportional to wiggle, and is wholly determined by wiggle, independent of how the wiggle was produced. Thus the effects of three different kinds of shape perturbation on letter identifiability are predicted by a single measure of goodness of continuation. This shows that letter identification obeys the Gestalt law of good continuation, and may be the first confirmation of the original Gestalt claim that object recognition involves grouping.

The same binding in contour integration and crowding

“…One advantage of using a letter identification task instead of the usual “snake in the grass” detection is that, by testing identification rather than detection, we can draw conclusions about object recognition. The contour integration task employed here is similar to the Pelli et al (2009) “snake letter” identification task, which measured the effect of alignment on object recognition.…”

“…A recent study goes beyond detection to establish the first direct link between good continuation and object recognition. The efficiency of identifying letters made up of gabors increased with the goodness of continuation between the gabors: efficiency was inversely proportional to “wiggle,” a measure of misalignment of the gabors (Pelli, Majaj, Raizman, Christian, Kim, & Palomares, 2009). That is, the better the gabors line up, the easier it is to identify the letter.…”

Learning to detect and combine the features of an object

“…1 to substitute thresholds for efficiencies, c HH = c HI c IH =c II : [4] Both equations correspond to the same dashed line in Fig. 2, using the threshold scale on the left (Eq.…”

“…Reading an hour a day for a year means identifying millions of letters and words. Each letter is a good basic-level object: simple, common, useful, and with its own name and shape (1)(2)(3)(4). Identifying a letter requires two steps of visual processing: the observer first detects the letter's features and then combines them to recognize the letter (5).…”

Cheaper by the dozen

“…Since a group of objects can be represented cognitively with summary statistics [3], recognition times for salient groups can be extremely rapid. Since items perceived as a group can "pop-out" from clutter [16,25], they can often be recognized as a whole more quickly and accurately than as individuals [1,24]. Accordingly, we model the time T Id (G, L) for a person to identify the label for a group as a function that is independent of the size of the group, but dependent on the numbers of labels to choose from.…”