The edge complex: implicit memory for figure assignment in shape perception

Viewing a stepped edge is likely to prompt the perceptual assignment of one side of the edge as figure. This study demonstrates that even a single brief glance at a novel edge gives rise to an implicit memory regarding which side was seen as figure; this edge complex enters into the figure assignment process the next time the edge is encountered, both speeding same-different judgments when the figural side is repeated and slowing these judgments when the new figural side is identical to the former ground side (Experiments 1A and 1B). These results were obtained even when the facing direction of the repeated edge was mirror reversed (Experiment 2). This study shows that implicit measures can reveal the effects of past experience on figure assignment, following a single prior exposure to a novel shape, and supports a competitive model of figure assignment in which past experience serves as one of many figural cues.     

Contour effects in figure perception

Summary Three experiments were performed to test the hypothesis that a target line that forms an outer contour of a stimulus figure is detected better than an internal target line. In the first experiment tridimensional stimuli similar to the object stimuli of Weisstein and Harris (1974), were used. In the second and third experiments arrows and triangles were used as stimuli, composed of one of the four right angles of a square and a diagonal. In the first two experiments the diagonal lines served as targets, and external diagonal lines were detected better than internal diagonals or diagonals without context. In the third experiment the right angles served as targets; these were detected better in arrows than in triangles or without the context diagonal. In each experiment the targets formed vertices and intersections with other line segments of the stimulus. It is argued that these local configurational features facilitated target detection by automatically attracting attention, particularly if they were located at the boundaries of the stimulus figure.This study was supported by grant Wa 419/1 of the Deutsche Forschungsgemeinschaft. The author wants to thank U. Bauer, J. Beringer, Cl. Gall, and U. Jacob for their help in performing the experiments     

Structural factors in figure perception

In this report, we examine tachistoscopic perception of lines in structured figures. Previous research has shown that perception of lines is facilitated when the lines occur as parts of coherent three-dimensional figures. Experiment 1 demonstrates that it is not necessary for the figure to be three-dimensional to obtain facilitation. Experiments 2 and 3 show that three-dimensionality is not sufficient either. What is important is that the target lines be structurally relevant to the figure. However, structural relevance of a target segment to the figure as perceived with unlimited viewing time is not perfectly correlated with perceptibility under tachistoscopic conditions; it appears that the targets which fall on the external contour of a figure may be facilitated even without a high degree of structural relevance. In view of this, we suggest a model in which perceivers use processing heuristics to direct processing to aspects of the input that are potentially important for determining the structure of the final figure, working primarily from the outside in.     

Incomplete figure perception and invisible masking

The Gollin test (measuring recognition thresholds for fragmented line drawings of everyday objects and animals) has traditionally been regarded as a test of incomplete figure perception or 'closure', though there is a debate about how such closure is achieved. Here, figural incompleteness is considered to be the result of masking, such that absence of contour elements of a fragmented figure is the result of the influence of an 'invisible' mask. It is as though the figure is partly obscured by a mask having parameters identical to those of the background. This mask is 'invisible' only consciously, but for the early stages of visual processing it is real and has properties of multiplicative noise. Incomplete Gollin figures were modeled as the figure covered by the mask with randomly distributed transparent and opaque patches. We adjusted the statistical characteristics of the contour image and empty noise patches and processed those using spatial and spatial-frequency measures. Across 73 figures, despite inter-subject variability, mean recognition threshold was always approximately 15% of total contour in naive observers. Recognition worsened with increasing spectral similarity between the figure and the 'invisible' mask. Near threshold, the spectrum of the fragmented image was equally similar to that of the 'invisible' mask and complete image. The correlation between spectral parameters of figures at threshold and complete figures was greatest for figures that were most easily recognised. Across test sessions, thresholds reduced when either figure or mask parameters were familiar. We argue that recognition thresholds for Gollin stimuli in part reflect the extraction of signal from noise.     

Phonetic categorization in auditory word perception

To investigate the interaction in speech perception of auditory information and lexical knowledge (in particular, knowledge of which phonetic sequences are words), acoustic continua varying in voice onset time were constructed so that for each acoustic continuum, one of the two possible phonetic categorizations made a word and the other did not. For example, one continuum ranged between the word dash and the nonword tash; another used the nonword dask and the word task. In two experiments, subjects showed a significant lexical effect--that is, a tendency to make phonetic categorizations that make words. This lexical effect was greater at the phoneme boundary (where auditory information is ambiguous) than at the ends of the condinua. Hence the lexical effect must arise at a stage of processing sensitive to both lexical knowledge and auditory information.     

Age-related changes in auditory temporal perception

The discrimination of signal and silence duration was evaluated in 6-month-old infants, 5 1/2-year-old children, and adults. Listeners were tested with a conditioned-discrimination procedure in which they were presented a sequence of 18 white-noise bursts and trained to discriminate a change in duration of the middle 6 signal or silence elements. There were no differential effects on performance for changes in signal compared to silence duration. At each age, performance varied only as a function of magnitude of duration change. Infants discriminated duration changes of 20 ms or greater, children discriminated 15 ms, and adults discriminated changes as small as 10 ms. These findings are consistent with other research in revealing age-related improvements in auditory temporal perception.     

Change perception in complex auditory scenes

In four experiments, we examined the role of auditory transients and auditory short-term memory in perceiving changes in a complex auditory scene comprising multiple auditory objects. Participants were presented pairs of complex auditory scenes that were composed of a maximum of four animal calls delivered in free field; participants were instructed to decide whether the two scenes were the same or different (Experiments 1, 2, and 4). Changes to the second scene consisted of either the addition or the deletion of one animal call. Contrary to intuitive predictions based on results from the visual change blindness literature, substantial deafness to the change emerged without regard to whether the scenes were separated by 500 msec of masking white noise or by 500 msec of silence (Experiment 1). In fact, change deafness was not even modulated by having the two scenes presented contiguously (i.e., 0-msec interval) or separated by 500 msec of silence (Experiments 2 and 4). This result suggests that change-related auditory transients played little or no role in change detection in complex auditory scenes. Instead, the main determinant of auditory change perception (and auditory change deafness) appears to have been the capacity of auditory short-term memory (Experiments 3 and 4). Taken together, these findings indicate that the intuitive parallels between visual and auditory change perception should be reconsidered.     

Feature mismatch effects in auditory negative

A handful of studies have revealed that withholding a response to a sound causes impaired responding to that sound when subsequently presented (Buchner & Steffens, 2001; Mondor, Leboe, & Leboe, 2005). In the present study, we investigated whether a switch in the location of a repeated sound might represent an additional source of this auditory negative priming effect. In all three of our experiments, participants performed a series of trials in which they withheld a response to a dichotic pair of prime sounds presented to each ear. A dichotic pair ofprobe sounds was then presented to each ear, and the participants were required to categorize one of them. Across these experiments, the participants were slower to categorize only repeated sounds that were presented in opposite locations.     

The homogeneity effect on figure/ground perception in infancy

We examined whether the homogeneity of the two profiles of Rubin's goblet affects figure/ground perception in infants. We modified the two profiles of Rubin's goblet in order to compare figure/ground perception under four test patterns: (1) two profiles painted with horizontal lines (horizontal-line condition), (2) two profiles painted middle gray (uni-color condition), (3) one profile painted light gray and the other dark gray (two-color condition), and (4) a goblet painted with concentric circles (concentric-circles condition). In the horizontal-line condition the homogeneity of the profile was strengthened, and in the two-color condition the homogeneity of the profile was weakened compared to the uni-color condition, which was an original Rubin's goblet. In the concentric-circles condition the homogeneity of the reversed areas of the horizontal-line were strengthened.     

Two types of auditory sequence perception

It has been suggested recently that there are two fundamentally distinct types of auditory sequence perception in man: (1) hofistic pattern recognition (HPR), operating for component item durations from a few milliseconds up to about 200 msec; and (2) direct identification of components and their order (Direct ICO), requiring verbal encoding of names for constituent sounds and requiring item durations roughly 200 msec and above for extended sequences. The present study, using only the very first judgments from 795 untrained participants presented with recycled three-item sequences, provided data consistent with this dichotomous formulation. In addition, it appeared that separate bursts of a noise band generated on-line were treated as different components in HPR and could not be used for sequence matching; “frozen” noise bursts having identical microstructure were treated as the same component and permitted HPR. On-fine noise bursts permitted Direct ICO, with naming based on long-term spectral characteristics of noise.     

Infants' perception of multiple-group auditory patterns

Six- and 12-month-old infants were tested for their perception of a variety of features of multiple-group auditory patterns. Each pattern comprised nine pure tones organized as three groupings each of three elements. The features examined included: (1) features having to do with frequency composition, designated as “local” pattern features; and (2) features involving relations between pattern components, designated as “global” pattern features. Infants were tested with a Go/No-Go conditioned head-turn procedure. Twelve-month-olds readily performed all discriminations. By contrast, 6-month-olds had greater difficulty discriminating local than global pattern features and showed limitations in their ability to organize three distinct groupings of elements into a unified pattern. Results are discussed with reference to infants' perception of features of single-group patterns and the notion of developmental changes in auditory information-processing capacities.     

The role of shape recognition in figure/ground perception in infancy

In this study we sought to determine whether infants, like adults, utilize previous experience to guide figure/ground processing. After familiarization to a shape, 5-month-olds preferentially attended to the side of an ambiguous figure/ground test stimulus corresponding to that shape, suggesting that they were viewing that portion as the figure. Infants’ failure to exhibit this preference in a control condition in which both sides of the test stimulus were displayed as figures indicated that the results in the experimental condition were not due to a preference between two figure shapes. These findings demonstrate for the first time that figure/ground processing in infancy is sensitive to top-down influence. Thus, a critical aspect of figure/ground processing is functional early in life.