Effects of task on the perceptual organization of sentences

Children and college students listened to sentences and responded to a question or a probe word after each sentence. To prevent Ss from using different perceptual strategies in performing the two tasks, question items and probe items were presented in mixed lists. In the probe task, the relationship between sentence structure and correct response latencies resembled the findings of an earlier study with block lists. The results from the question task were less similar to those obtained earlier, perhaps because, with mixed lists, Ss tended to organize all sentences in a manner especially suited to the probe task. A different type of organization might be used in the process of comprehending a sentence solely for the purpose of answering questions.     

The relationship between visual persistence and event perception in bistable motion display

Observers viewed two alternating frames, each consisting of three rectangular bars displaced laterally by one cycle in one frame with respect to the other. At long interframe intervals (IFIs) observers perceived a group of three bars moving as a whole (group motion), and at short IFIs the overlapping elements in the two frames appeared stationary, while the third element appeared to move from one end of the display to the other (element motion). The upper temporal limit for perceiving element motion was reduced when bars with blurred edges were used and when either frame duration or bar size was increased. However, when inner and outer elements had different sizes, the element motion percept was dominant up to 230 ms IFI. These findings may be interpreted in terms of spatial tuning of motion mechanisms involved in the perception of bistable apparent motion.     

Principles of perceptual organization and spatial distortion: the gestalt illusions

In five interleaved experiments, conducted with 94 observers, it is shown that organization of the visual field according to gestalt principles results in measurable spatial distortions. Using the principles of proximity, similarity, good continuation, and two types of closure, it was found that interior distances (within a perceptual unit or group) are underestimated relative to exterior distances. The relationship between these spatial distortions and the resultant perceptual organization are discussed.     

Effects of stimulus synchrony on mechanisms of perceptual organization

When neurons adopt a synchronized, oscillatory response to stimulus Gestalten, the phase of those oscillations almost always varies relative to stimulus activity. This has been taken to indicate that form-coding mechanisms are synchronized by internal timing mechanisms, and/or may be sensitive to stimulus activity only via motion detectors. This proposal is problematic for interpreting recent demonstrations of the effects of stimulus synchrony particularly when stimuli are stationary. Here we offer an account of stimulus-driven synchronization supported by evidence that segmentation by stimulus synchrony can be relatively insensitive to explicit motion signals. The argument is made that qualitative similarities between the effects of phase-independent and phase-locked oscillations in the EEG, the effects of phase synchronization at the cellular level and evidence for phase-enhanced stimulus grouping should be considered as functionally equivalent. This argument emphasizes the flexibility of temporal synchrony as a code for perceptual organization.     

Effects of similarity on apparent motion and perceptual grouping

Effects of similarity in colour, luminance, size, and shape on apparent motion and perceptual grouping were examined in part 1 in two parallel experiments on the same seven subjects. In both experiments, the effect of similarity was compared with that of proximity in competitive, bistable stimulus situations. A combination of a larger horizontal separation between the homogeneous stimulus elements and a smaller constant vertical separation between heterogeneous stimulus elements produced two kinds of apparent motion (or perceptual grouping) with equal probabilities. Such matched separations between homogeneous stimulus elements were obtained by the double staircase method in various stimulus conditions. In both experiments on apparent motion and perceptual grouping matched separation was found to increase as the difference between the heterogeneous stimulus elements increased. High correlations (0.71 to 0.94) of matched separations were found between apparent motion and perceptual grouping in four stimulus series: colour, luminance, size, and shape. Six of the seven subjects were also tested in part 2. Here, the effects of differences were found to work additively across different perceptual attributes in both phenomena, when multiple differences were combined in heterogeneous elements. The experimental results are discussed from the point of view that apparent motion is an example of perceptual constancy.     

Color aftereffects contingent on perceptual organization

The present experiment demonstrated that (a) cognitive organizational factors influence an orientation-contingent color (McCollugh) aftereffect, and (b) adaptation to colored gratings affected the perceptual organization of a reversible figure. Following adaptation to colored gratings, color aftereffects were reported in only one of two organizations of a reversible figure, and the colors conformed to the subjective contours of the test pattern rather than exclusively to the regions defined by horizontal and vertical pattern elements. In addition, an organization of the reversible figure that segregated vertical and horizontal pattern elements was dominant subsequent to adaptation.     

Multiplicative effects of intention on the perception of bistable apparent motion

When viewing ambiguous displays, observers can, via intentional efforts, affect which perceptual interpretation they perceive. Specifically, observers can increase the probability of seeing the desired percept. Little is known, however, about how intentional efforts interact with sensory inputs in exerting their effects on perception. In two experiments, the current study explored the possibility that intentional efforts might operate by multiplicatively enhancing the stimulus-based activation of the desired perceptual representation. Such a possibility is suggested by recent neurophysiological research on attention. In support of this idea, when we presented bistable apparent motion displays under stimulus conditions differentially favoring one motion percept over the other, observers' intentional efforts to see a particular motion were generally more effective under conditions in which stimulus factors favored the intended motion percept.     

A microcomputer-based tracking task for examination of the spatial and temporal organization of perceptual motor skill

A microcomputer-based tracking task is described in detail. The program that controls this task was written in Pascal and 6502 assembler language and was designed to run on an Apple IIe computer. The program was designed to allow the experimenter to vary such parameters as the velocity of the stimulus signal. In addition, several indicants of performance are recorded simultaneously and are averaged over selected time intervals during each trial. The paper also illustrates the applications of this particular computer program in the study of motor control and learning.     

Illusory concomitant motion in ambiguous stereograms: evidence for nonstimulus contributions to perceptual organization

Three experiments were performed to test whether perceptual organization is cognitively or motivationally penetrable. In Experiments 1 and 2, subjects viewed a reversible stereogram while instructed to hold one depth organization. Responses about depth were recorded indirectly by recording responses about direction of the illusory concomitant motion that is perceptually coupled to depth in a stereogram. Inasmuch as perceptually coupled variables covary without necessary stimulus covariation, a post-perceptual locus for any intention effects they exhibit is unlikely. Experiments 2 and 3 examined the possibility that instructed intention might influence perception indirectly by influencing eye movements: Viewers' vergence position was measured directly through responses about alignment of a vernier nonius fixation. In all three experiments, a residual effect of instructed intention was found. Therefore, instructed intention may influence perceptual organization by influencing internal nonstimulus components integral to the perceptual process.     

The effects of position cues on the appearance of stimulus elements in a bistable apparent movement display

A modified version of the Ternus display was used to assess the relative effects of element position cues on reports of group and end-to-end movement. In this display, two rows of stimulus elements are joined by connecting lines. In one version of the display, the connecting lines remain stationary across frames, facilitating the interpretation that the associated stimulus elements also remain stationary. In another version of the display, one end of the connecting lines shifts horizontally from frame to fame, facilitating the interpretation that the associated stimulus elements have also shifted. The experiment showed that when the connecting lines remain stationary, reports of end-to-end movement increase, regardless of the interstimulus interval (ISI) at which the frames alternate. When the connecting lines shift, reports of group movement increase, regardless of ISI. Theoretical interpretations of the results involving both relatively low-level motion signals and higher order perceptual influences are considered.     

The perceptual organization of dot lattices

Bravais (1850/1949) demonstrated that there are five types of periodic dot patterns (or lattices): oblique, rectangular, centered rectangular, square, and hexagonal. Gestalt psychologists studied grouping by proximity in rectangular and square dot patterns. In the first part of the present paper, I (1) describe the geometry of the five types of lattices, and (2) explain why, for the study of perception, centered rectangular lattices must be divided into two classes (centered rectangular andrhombic). I also show how all lattices can be located in a two-dimensional space. In the second part of the paper, I show how the geometry of these lattices determines their grouping and their multistability. I introduce the notion ofdegree of instability and explain how to order lattices from most stable to least stable (hexagonal). In the third part of the paper, I explore the effect of replacing the dots in a lattice with less symmetric motifs, thus creating wallpaper patterns. When a dot pattern is turned into a wallpaper pattern, its perceptual organization can be altered radically, overcoming grouping by proximity. I conclude the paper with an introduction to the implications of motif selection and placement for the perception of the ensuing patterns.     

Asynchrony tolerance in the perceptual organization of speech

Researchers have claimed that listeners tolerate large temporal distortion when integrating the spectral components of speech. In some estimates, perceivers resolve linguistic attributes at spectral desynchronies as great as the duration of a syllable. We obtained new measures of perceptual tolerance of auditory asynchrony, using sine-wave synthesis in order to require perceivers to resolve the speech stream dynamically. Listeners transcribed sentences in which the tone analogue of a second formant was desynchronized relative to the remaining tones of a sentence, with desynchrony ranging from a 250-msec lead to a 250-msec lag. Intelligibility declined symmetrically from 72% at synchrony to 7% at 6100 msec. This finding of narrow asynchrony tolerance indicates a time-critical feature of the auditory perceptual organization of speech     

Modulation sensitivity in the perceptual organization of speech

In a spoken utterance, a talker expresses linguistic constituents in serial order. A listener resolves these linguistic properties in the rapidly fading auditory sample. Classic measures agree that auditory integration occurs at a fine temporal grain. In contrast, recent studies have proposed that sensory integration of speech occurs at a coarser grain, approximate to the syllable, on the basis of indirect and relatively insensitive perceptual measures. Evidence from cognitive neuroscience and behavioral primatology has also been adduced to support the claim of sensory integration at the pace of syllables. In the present investigation, we used direct performance measures of integration, applying an acoustic technique to isolate the contribution of short-term acoustic properties to the assay of modulation sensitivity. In corroborating the classic finding of a fine temporal grain of integration, these functional measures can inform theory and speculation in accounts of speech perception.     

Human visual perceptual organization beats thinking on speed

What is the degree to which knowledge influences visual perceptual processes? This question, which is central to the seeing-versus-thinking debate in cognitive science, is often discussed using examples claimed to be proof of one stance or another. It has, however, also been muddled by the usage of different and unclear definitions of perception. Here, for the well-defined process of perceptual organization, I argue that including speed (or efficiency) into the equation opens a new perspective on the limits of top-down influences of thinking on seeing. While the input of the perceptual organization process may be modifiable and its output enrichable, the process itself seems so fast (or efficient) that thinking hardly has time to intrude and is effective mostly after the fact.