Feature sampling in detection: implications for the measurement of perceptual independence

The article presents the feature sampling signal detection (FS-SDT) model, an extension of the multivariate signal detection (SDT) model. The FS-SDT model assumes that, because of attentional shifts, different subsets of features are sampled for different presentations of the same multidimensional stimulus. Contrary to the SDT model, the FS-SDT model enables the estimation of pure perceptual effects that are uncontaminated by strategic attention shifts. The consideration of feature sampling in detection and identification opens a new perspective on the problem of measuring, respectively, the separability and integrality of stimulus dimensions. Disregarding feature sampling as a component process in detection and identification usually results in biased estimations of perceptual independence concepts relevant for judgments of whether stimulus dimensions are processed independently.     

The complementarity of apparent and real motion

Summary It is proposed that apparent motion does not parallel real motion. Bather, apparent motion occurs when the off-period is equivalent to angular velocities at which an object in real motion appears blurred. Experimental evidence is reported which supports this view. It suggests that apparent motion serves biologically to extend the range of motion perception beyond that allowed by time-constants early in the visual system.     

Perceptual and decisional contributions to audiovisual interactions in the perception of apparent motion: a signal detection study

Motion information available to different sensory modalities can interact at both perceptual and post-perceptual (i.e., decisional) stages of processing. However, to date, researchers have only been able to demonstrate the influence of one of these components at any given time, hence the relationship between them remains uncertain. We addressed the interplay between the perceptual and post-perceptual components of information processing by assessing their influence on performance within the same experimental paradigm. We used signal detection theory to discriminate changes in perceptual sensitivity (d') from shifts in response criterion (c) in performance on a detection (Experiment 1) and a classification (Experiment 2) task regarding the direction of auditory apparent motion streams presented in noise. In the critical conditions, a visual motion distractor moving either leftward or rightward was presented together with the auditory motion. The results demonstrated a significant decrease in sensitivity to the direction of the auditory targets in the crossmodal conditions as compared to the unimodal baseline conditions that was independent of the relative direction of the visual distractor. In addition, we also observed significant shifts in response criterion, which were dependent on the relative direction of the distractor apparent motion. These results support the view that the perceptual and decisional components involved in audiovisual interactions in motion processing can coexist but are largely independent of one another.     

Salience modulation in serial preexposure: implications for perceptual learning

In three experiments rats were given serial preexposure to two flavor stimuli. In Experiment 1, some animals were given exposure to AX followed by the presentation of BX, a forward schedule; the others were given backward preexposure (BX→AX). Conditioning and test trials with the A element showed that salience or effectiveness of A was better protected in the forward than in the backward condition. Experiments 2 and 3 assessed the relevance of this salience modulation mechanism for perceptual learning. In these experiments, generalization of a conditioned aversion from AX to BX was reduced in the forward (but not in the backward) condition only after prolonged exposure, indicating that the establishment of an inhibitory link from B to A is required for successful discrimination. However, generalization to a novel compound stimulus, NX, was reduced in the forward group both after short and long preexposure, suggesting the existence of salience modulation processes that work in parallel with associative inhibition. These results seem to support the existence of a salience modulation mechanism that seems to be beyond the scope of current theories of perceptual learning.     

Manual and virtual rotation of a three-dimensional object

An orientation-matching task, based on a mental rotation paradigm, was used to investigate how participants manually rotated a Shepard-Metzler object in the real world and in an immersive virtual environment (VE). Participants performed manual rotation more quickly and efficiently than virtual rotation, but the general pattern of results was similar for both. The rate of rotation increased with the starting angle between the stimuli meaning that, in common with many motor tasks, an amplitude-based relationship such as P. M. Fitts' (1954) law is applicable. When rotation was inefficient (i.e., not by the shortest path), it was often because participants incorrectly perceived the orientation of one of the objects, and this happened more in the VE than in the real world. Thus, VEs allow objects to be manipulated naturally to a limited extent, indicating the need for timing-scale factors to be used for applications such as method-time-motion studies of manufacturing operations.     

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 perceptual fate of letters in two kinds of apparent movement displays

Two experiments investigated the importance of figurai relationships among stimulus elements in the determination of the kind of motion perceived in bistable apparentovement displays. Stimulus frames containing the words MITE and ITEM were constructed in such a way that the letters I, T, and E appeared in corresponding locations while the M was in disparate locations between frames. When the frames were alternated with a 20-msec ISI, observers maintained local figurai identity in their percepts of apparent movement. However, when the frames were alternated with an 80-msec ISI, observers reported apparent movement of the entire groups of letters and thereby ignored figurai relationships in their percepts of apparent movement. In a second experiment, it was found that figurai nonidentity between elements of successive frames always resulted in apparent movement of a perceptual group or “blob” regardless of ISI. It is suggested that short-range apparent-movement percepts rely strongly upon figurai identity among corresponding stimulus elements, whereas long-range apparent-movement percepts do not.     

The language environment of the young infant: implications for early perceptual development

The purpose of this article is to review recent research on the young infant's use of voice-specific as well as voice-nonspecific auditory information during early language processing, to suggest a possible mechanism that biases the young infant towards this information, and to discuss potential implications of the early saliency of this information for later language development. Auditory preferences expressed by young infants are of interest because they demonstrate which properties of complex auditory events are effective in capturing the infant's attention. Moreover, the presence of such auditory preferences has led to speculations about their possible origins in both pre- and postnatal auditory experience. Research examining the role of early auditory experience in the formation of preferences is presented, along with a discussion of how the constrained nature of early auditory experience (particularly prenatal) may bias the young infant towards specific features of maternal as well as nonmaternal speech.     

Evidence for criterion shifts in visual perceptual learning: data and implications

Work on visual perceptual learning for contrast detection has shown that reliable decreases in detection thresholds are accompanied by reliable increases in false alarm rates (Wenger & Rasche, 2006). The present study assesses the robustness and replicability of these changes, demonstrating that they are independent of a variety of task demands (i.e., the specific method used for perceptual practice and threshold estimation) and the presence or absence of trial-by-trial feedback and that the source of the increases can be found in shifts in changes in sensitivity and in bias for detection, identification, or both. Although the increase in false alarm rates suggests a strategic shift in response criteria for detection, we demonstrate that there are multiple potential explanations, including explanations that do not require strategic shifts on the part of the observer. The empirical evidence and analysis of alternative explanations reinforce the inference that visual perceptual learning may involve more than changes in perceptual sensitivity and that cortical circuits beyond the primary visual areas may be involved.     

The perceptual nature of audiovisual interactions for semantic knowledge in young and elderly adults

Audiovisual interactions for familiar objects are at the core of perception. The nature of these interactions depends on the amodal – sensory abstracted – or modal – sensory-dependent – approach of knowledge. According to these approaches, the interactions should be respectively semantic and indirect or perceptual and direct. This issue is therefore a central question to memory and perception, yet the nature of these interactions remains unexplored in young and elderly adults. We used a cross-modal priming paradigm combined with a visual masking procedure of half of the auditory primes. The data demonstrated similar results in the young and elderly adult groups. The mask interfered with the priming effect in the semantically congruent condition, whereas the mask facilitated the processing of the visual target in the semantically incongruent condition. These findings indicate that audiovisual interactions are perceptual, and support the grounded cognition theory.     

The effects of perceptual set on the shape and apparent depth of subjective contours

Two experiments showed the influence of perceptual set on the perception of subjective contours. In the first, the perceived shape of a subjective-contour figure (a minimal version of the Ehrenstein configuration) was varied by altering the observer’s viewing set. The second experiment showed that apparent depth emerged in subjective-contour figures when observers were set to perceive the illusory contours.     

The role of attentional breadth in perceptual change detection

Previous research has shown that changes to scenes are often surprisingly hard to detect. The research reported here investigated the relationship between individual differences in attention and change detection. We did this by assessing participantś breadth of attention in a functional field of view task (FFOV) and relating this measure to the speed with which individuals detected changes in scenes. We also examined how the salience, meaningfulness, and eccentricity of the scene changes affected perceptual change performance. In order to broaden the range of individual differences in attentional breadth, both young and old adults participated in the study. A strong negative relationship was obtained between attentional breadth and the latency with which perceptual changes were detected; observers with broader attentional windows detected changes faster. Salience and eccentricity had large effects on change detection, but meaning aided the performance of young adults only and only when changes also had low salience.     

Relativistic effects in visual perception of real and apparent motion

Timing in the visual field is regarded as an additive conjoint measurement structure, psychophysical extension of stimulus path as an extensive measurement structure. These two sets of postulates lead to the derivation of an essential maximum for velocity perception. Apparent phi motion perception under strictly stationary stimulus conditions is described as relative motion of the first stimulus' psychophysical mapping with respect to a moving perceptual subsystem. The essential maximum of velocity modifies the relative motion postulate: relativistic dilatation of seen length of path is predicted. Testable properties of the model, comparison with experimental data from "real" motion and apparent phi motion perception are discussed.     

Illusory three-dimensional rotation of horizontal lines: a new motion-depth illusion.

A new motion--depth illusion is reported. When a curved aperture translates vertically and stationary horizontal lines can be seen through it, the line lengths on the retina change continuously because of the occlusion. Instead of seeing the aperture translate, subjects sometimes see the lines rotate in depth around a vertical axis. This is a rare kind of illusion: an ambiguous motion which can be seen as either stationary in two dimensions or rotating in three dimensions. Three-dimensional rotation was more often observed when the luminance difference between the horizontal lines and the background was larger than that between the aperture and the background. This illusion demonstrates that motion detection and the structure-from-motion process correlate with figure--ground segregation, depth stratification, and figural-completion processes based on luminance contrast.     

The hidden face of Kanizsa's triangle: apparent movement of subjective figures in three-dimensional space

Several demonstrations on the apparent movement in depth of subjective figures are presented. They include: (a) apparent rotational movement as a result of shape invariance or rigidity; (b) apparent rotational movement with three-dimensional subjective figures not accompanied by a brightness gradient; and (c) apparent rotational movement by kinetic occlusion.     

The unilateral field advantage in repetition detection: Effects of perceptual grouping and task demands

This study examines interhemispheric interactions in detecting objects that are simultaneously repeated in an array of objects. Previous studies have shown that presenting two identical objects to a single hemifield speeds up repetition detection. This unilateral field advantage (UFA) is often attributed to the relatively low-level processing demands for detecting a perceptual repetition, and more specifically, to more efficient perceptual grouping processes within a hemisphere than between hemispheres. To directly examine the impact of perceptual grouping and task demands on interhemispheric interactions, we asked participants to judge whether four items, one presented in each visual quadrant, were all different, or whether any two were the same, along an instructed dimension. We found that in comparison with the UFA for identical objects, the UFA for repetition detection in accuracy was similar or greater when the matching objects were not perceptually identical and differed in color, size, or viewpoint. Thus, decreasing grouping strength and increasing computational complexity did not reduce the UFA. Results are interpreted in terms of the callosal degradation account of the UFA.     

Processing linguistic and perceptual dimensions of speech: interactions in speeded classification.

Performance on selective-attention and divided-attention tasks shows strong and consistent interactions when participants rapidly classify auditory stimuli whose linguistic and perceptual dimensions (the words low vs. high, low and high pitch, low and high position in space) share common labels. Compared with baseline performance, response times were greater when one or two irrelevant dimensions varied (Garner interference) and when combinations of attributes were incongruent rather than congruent (congruence effects). Performance depended only on the congruence relationships between the relevant dimension and each of the irrelevant dimensions and not on the congruence relationships between the irrelevant dimensions themselves. In selective attention, an additive multidimensional model accounts well for the patterns of both Garner interference and congruence effects.