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Publications (187)
When subjects are asked to indicate the center of a spatially distributed stimulus, the features that control their responses tend to vary (1) across subjects and (2) as stimulus properties are altered. Here we ask: can subjects bring these different response tendencies under top-down control? In each of three tasks, all using briefly displayed, Ga...
Substantial evidence suggests that sensitivity to the difference between the major vs minor musical scales may be bimodally distributed. Much of this evidence comes from experiments using the “3-task.” On each trial in the 3-task, the listener hears a rapid, random sequence of tones containing equal numbers of notes of either a G major or G minor t...
This paper introduces a new method to determine how subjects make discriminations among red-green texture stimuli. More specifically, the method determines (1) the number of mechanisms in human vision sensitive to lights that vary along the constant-S cardinal axis (cSCA) of DKL space and (2) the sensitivity of each mechanism to cSCA lights. Each o...
Human vision is highly efficient in estimating the centroids of spatially scattered items. However, the processes underlying this remarkable skill remain poorly understood. A salient fact is that in estimating the centroids of dot-clouds, observers underweight densely packed dots relative to isolated dots; thus, when an observer estimates the centr...
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ABSTRACT
When listeners try to discriminate rapid pure-tone sequences (“tone scrambles”) whose frequencies come from a major set (G5, B5, D6, and G6) versus a minor set (G5, B♭5, D6, and G6), most (≈70%) perform near chance (Chubb et al., 2013). The rest perform near ceiling. The variation in performance is largely explained by pos...
The difference between major and minor scales plays a central role in Western music. However, recent research using random tone sequences ("tone-scrambles") has revealed a dramatically bimodal distribution in sensitivity to this difference: 30% of listeners are near perfect in classifying major versus minor tone-scrambles; the other 70% perform nea...
When classifying major versus minor tone-scrambles (random sequences of pure tones), most listeners (70%) perform at chance while the remaining listeners perform nearly perfectly. The current study investigated whether inserting rests and cyclic sequences into the stimuli could heighten sensitivity in such tasks. In separate blocks, listeners class...
In this paper we set up to enumerate and characterize mechanisms sensitive to color scrambles. A color scramble is a texture made of a finite number of elements drawn from a set Ω, in this case small colored squares, distributed according to a histogram. We use a novel method to derive a eight equiluminant lights along the Red-Green cardinal axis....
In this paper we set up to enumerate and characterize mechanisms sensitive to color scrambles. A color scramble is a texture made of a finite number of elements drawn from a set Ω, in this case small colored squares, distributed according to a histogram. We use a novel method to derive a eight equiluminant lights along the Red-Green cardinal axis....
Hick's law describes the relation between choice reaction time (RT) and the number of stimulus-response alternatives (NA). For over half a century, this uncertainty effect has been ascribed primarily to the time taken to map a stimulus to its associated response. Here, data from 2 experiments suggests that selection of the appropriate effector-the...
Visual features such as edges and corners are carried by high-order statistics. Previous analysis of discrimination of isodipole textures, which isolate specific high-order statistics, demonstrates visual sensitivity to these statistics but stops short of analyzing the underlying computations. Here we use a new texture centroid paradigm to probe th...
In a selective centroid task, the participant views a brief cloud of items of different types-some of which are targets, the others distractors-and strives to mouse-click the centroid of the target items, ignoring the distractors. Advantages of the centroid task are that multiple target types can appear in the same display and that influence functi...
statistical representations are aggregate properties of the environment that are presumed to be perceived automatically and preattentively. We investigated two tasks presumed to involve these representations: judgments of the centroid of a set of spatially arrayed items and judgments of the mean size of the items in the array. The question we ask i...
Significance
A critical visual process is segmenting a scene into objects to be processed (foreground) and the remainder (background). Humans are extraordinarily good at segmentation, but how they accomplish this still is not well understood. An important component process in segmentation is grouping by similarity, for example, by color, shape, siz...
A tone-scramble is a random sequence of pure tones. Previous studies have found that most listeners (≈ 70%) perform near chance in classifying rapid tone-scrambles composed of multiple copies of notes in G-major vs G-minor triads; the remaining listeners perform nearly perfectly [Chubb, Dickson, Dean, Fagan, Mann, Wright, Guan, Silva, Gregersen, an...
This study investigated how cuttlefish (Sepia officinalis) camouflage patterns are influenced by the proportions of different gray-scales present in visually cluttered environments. All experimental substrates comprised spatially random arrays of texture elements (texels) of five gray-scales: Black, Dark gray, Gray, Light gray, and White. The subst...
Visual textures are a class of stimuli with properties that make them well suited for addressing general questions about visual function at the levels of behavior and neural mechanism. They have structure across multiple spatial scales, they put the focus on the inferential nature of visual processing, and they help bridge the gap between stimuli t...
A tone-scramble is a rapid, randomly ordered sequence of pure tones. Chubb, Dickson, Dean, Fagan, Mann, Wright, Guan, Silva, Gregersen, and Kowalski [(2013). J. Acoust. Soc. Am. 134(4), 3067–3078] showed that a task requiring listeners to classify major vs minor tone-scrambles yielded a strikingly bimodal distribution. The current study sought to c...
Visual illusions cut across academic divides and popular interests: on the one hand, illusions provide entertainment as curious tricks of the eye; on the other hand, scientific research related to illusory phenomena has given generations of scientists and artists deep insights into the brain and principles of mind and consciousness. Numerous thinke...
Visual illusions cut across academic divides and popular interests: on the one hand, illusions provide entertainment as curious tricks of the eye; on the other hand, scientific research related to illusory phenomena has given generations of scientists and artists deep insights into the brain and principles of mind and consciousness. Numerous thinke...
Significance
The eyes present the brain much more information than it could possibly process. One important way to prioritize information is by selective attention to features, processing only items containing the attended features and blocking others (i.e., forming an attention filter). Here we demonstrate an extremely efficient paradigm and a pow...
The visual images in the eyes contain much more information than the brain can process. An important selection mechanism is feature-based attention (FBA). FBA is best described by attention filters that specify precisely the extent to which items containing attended features are selectively processed and the extent to which items that do not contai...
Rationale. Visual features, such as edges and corners, are carried by high-order statistics (also known as multipoint correlations or phase correlations). Analysis of discrimination of "isodipole" textures, which isolate specific kinds of high-order statistics, demonstrates visual sensitivity to these statistics but stops short of analyzing the und...
The visual search literature consistently reports a "pop out" effect for targets defined by a single feature. For such targets, reaction time does not change as a function of display size. When targets are defined by a conjunction of features, however, reaction time increases as a function of display size (e.g. Treisman & Gelade, Cognitive Psycholo...
How efficiently can the visual system use stimulus information in a briefly viewed cloud of dots for two different purposes: judging the number of dots in the cloud (numerosity) versus estimating the cloud's center-of-gravity (its centroid)? These two statistical summary statistics can be estimated rapidly and quite accurately even in very brief st...
This paper elaborates a recent conceptualization of feature-based attention in terms of attention filters (Drew et al., Journal of Vision, 10(10:20), 1-16, 2010) into a general purpose centroid-estimation paradigm for studying feature-based attention. An attention filter is a brain process, initiated by a participant in the context of a task requir...
The finding that an item of type A pops out from an array of distractors of type B typically is taken to support the inference that human vision contains a neural mechanism that is activated by items of type A but not by items of type B. Such a mechanism might be expected to yield a neural image in which items of type A produce high activation and...
Features that support "pop out" in visual search are often assumed to be associated with preattentive mechanisms that can support feature-based attention in other tasks. We have found that this assumption holds for luminance and hue; however, a companion presentation shows that, although differences in absolute bar-orientation support pop out, this...
It is well documented that a vertical bar will pop out amongst many horizontal bars. Since this search task is so natural and automatic, and because orientation selective cells are so widespread in early visual areas, it is commonly assumed that people have access to preattentive mechanisms tuned to vertical bars and not horizontal ones. These mech...
To judge the mean location (centroid) of only a set of black dots when they are spatially intermingled with white dots, one needs a mechanism that passes information carried by the to-be-attended visual feature (black) across space (all locations of black dots) onto further mental processes while blocking the passage of the information carried by t...
The visual system is biased toward negative luminance contrast. In particular, texture discrimination performance is dominated by a "blackshot" mechanism that is sensitive to the lowest luminances in the image (Chubb et al. 2004, Vision Research). However, it is unclear whether the tuning of this mechanism is absolute (driven by luminance near blac...
What are the basic image attributes sensed by human vision? This fundamental question has proved difficult to answer experimentally. We introduce a novel psychophysical method that provides leverage for addressing this question in the context of visual texture perception. On each trial, the participant sees a brief display comprising a randomly pos...
What preattentive mechanisms are sensitive to scrambles (spatially random mixtures) of colors from the L-M cardinal axis of DKL space?
On a trial, the participant strove to localize a circular target patch of color-scramble with one histogram in a large, annular background color-scramble with a different histogram. Scrambles were composed of eight...
In the Barber-Pole Illusion (BPI), a diagonally moving grating is perceived as moving vertically because of the narrow, vertical, rectangular shape of the aperture window through which it is viewed. This strong shape-motion interaction persists through a wide range of parametric variations in the shape of the window, the spatial and temporal freque...
We review recent research on the visual mechanisms of rapid adaptive camouflage in cuttlefish. These neurophysiologically complex marine invertebrates can camouflage themselves against almost any background, yet their ability to quickly (0.5-2 s) alter their body patterns on different visual backgrounds poses a vexing challenge: how to pick the cor...
Lateral inhibition is thought to underlie most forms of contextually induced repulsion. Examples include simultaneous contrast and the tilt illusion. It may seem strange that evolution has favoured a sensory apparatus that distorts the relationships between its stimuli, but it is possible that such distortion is accompanied by an increase in sensit...
Introduction. Success in filtering irrelevant information depends on the relative salience of attended and unattended features, and the attentive demands of the task (Lavie, 2004). In difficult tasks, high salience features are robust against the interfering potential of irrelevant distractors, even when the distractors are also highly salient (Lu...
Previous research supports the claim that human vision has three dimensions of sensitivity to grayscale scrambles (textures composed of randomly scrambled mixtures of different grayscales). However, the preattentive mechanisms (called here "field-capture channels") that confer this sensitivity remain obscure. The current experiments sought to chara...
In the barber-pole illusion (BPI), a diagonally moving grating is perceived as moving vertically because of the shape of the vertically oriented window through which it is viewed-a strong shape-motion interaction. We introduce a novel stimulus-the moving barber pole-in which a diagonal, drifting sinusoidal carrier is windowed by a raised, vertical,...
Provides quantitative data about a two or more dimensional image. Classifies and counts number of entities an image contains. Each entity comprises a structure, or some other type of identifiable portion having definable characteristics. The entities located within an image may have different shape, color, texture, etc., but still belong to the sam...
This study investigated the abilities of listeners to classify various sorts of musical stimuli as major vs minor. All stimuli combined four pure tones: low and high tonics (G5 and G6), dominant (D), and either a major third (B) or a minor third (B♭). Especially interesting results were obtained using tone-scrambles, randomly ordered sequences of p...
Sound streams were generated by randomly choosing the levels of tone pips from two different distributions, A and B. Of the 18 tone pips, the first nine were drawn from distribution A and the second nine from distribution B, or the opposite. The listeners' task was to indicate order, A-B or B-A. In two conditions the A and B distributions differed...
Background / Purpose:
1. To measure the relative contribution of short (S), middle (M), and long (L) wavelength sensitive cones to luminance as gauged with a minimum motion task (Anstis and Cavanagh, 1983). 2. To assess the direction of the motion-luminance axis as we change luminance level; we called motion-luminance axis the axis orthogonal to...
Purpose: In judging the centroid (center of gravity) of a random cloud of dots, it has previously been determined that subjects can give approximately equal attentional weight only to dots lighter than the background (ignoring dots darker than the background), only to dots darker than the background (ignoring light dots) or to all dots (Drew, Chubb...
Purpose: To measure how well humans can isolate a target color among heterogeneous distracter colors.
Method: We used a centroid-estimation task to quantify this ability. For each subject, we first used a minimum motion paradigm to obtain 8 equiluminant lights evenly spaced around an ellipse in the space spanned by the (Stockman-Sharpe) cone fundam...
Previous research has shown that human vision has three dimensions of sensitivity to grayscale scrambles (spatially random mixtures of different grayscales). However, the mechanisms that confer this sensitivity remain obscure. The current experiments resolve this issue by focusing on search asymmetries revealed when the participant is required to l...
In foveal view, the moving barberpole stimulus looks like several barber poles drifting horizontally. It is produced by a diagonal sinusoidal carrier grating with bars drifting up to the right, windowed by a raised, vertical, horizontally-drifting sinusoid. Unlike stationary barber poles, the rigid-motion direction of this stimulus is diagonal, not...
Background / Purpose:
The visual system is sensitive to many kinds of image statistics, including those of low and high order; in natural scenes, these different kinds of image statistics are intertwined in a complex fashion. This motivated the development of a library of synthetic images that enables testing the salience of individual image stat...
Rapid adaptive camouflage is the primary defense of soft-bodied cuttlefish. Previous studies have shown that cuttlefish body patterns are strongly influenced by visual edges in the substrate. The aim of the present study was to examine how cuttlefish body patterning is differentially controlled by various aspects of edges, including contrast polari...
A fundamental question in vision science is: Which physical differences in the visual input are spontaneously visible and which are not? At present this question has only been partially answered. We propose that spontaneously visible variations are coded in “field-capture channels” that compute statistics on the raw visual input and pass them on to...
We introduce a stimulus whose perceptual properties call into question current models of first-order motion processing. This stimulus consists of a diagonal sinusoidal carrier grating with bars drifting up to the left, windowed by a raised, vertical, drifting sinusoid. In slow motion, this stimulus represents a row of barber poles with blurred edge...
The motion direction of a moving sinewave grating is ambiguous. The motion of a plaid, consisting of any two arbitrary translating sinewave gratings is not ambiguous; there is always rigid direction that corresponds to a translation of a snapshot of the plaid. The rigid direction can be determined by the "intersection of constraints" (Adelson & Mov...
Background / Purpose:
To investigate how hue is coded for purposes of processing texture. Specifically, we test a model proposing that hue-selective units all share tuning functions of the same shape F but centered on different hues so as to achieve uniform coverage around the hue circle.
Main conclusion:
If all hues were created equal, then t...
Background / Purpose:
We used a selective attention task to discover the ways in which observers could combine auditory and visual information (loudness and brightness). We also wanted to test the temporal limit of multimodal binding established by Fujisaki and Nishida (1).
Main conclusion:
There were three dimensions of brightness/loudness at...
Recent evidence suggests that the speech motor system may play a significant role in speech perception. Repetitive transcranial magnetic stimulation (TMS) applied to a speech region of premotor cortex impaired syllable identification, while stimulation of motor areas for different articulators selectively facilitated identification of phonemes rely...
Previous studies investigating transfer of perceptual learning between luminance-defined (LD) motion and texture-contrast-defined (CD) motion tasks have found little or no transfer from LD to CD motion tasks but nearly perfect transfer from CD to LD motion tasks. Here, we introduce a paradigm that yields a clean double dissociation: LD training yie...
Why do the equally spaced dots in figure 1 appear regularly spaced? The answer 'because they are' is naive and ignores the existence of sensory noise, which is known to limit the accuracy of positional localization. Actually, all the dots in figure 1 have been physically perturbed, but in the case of the apparently regular patterns to an extent tha...
Different laboratories have achieved a consensus regarding how well human observers can estimate the average orientation in a set of N objects. Such estimates are not only limited by visual noise, which perturbs the visual signal of each object's orientation, they are also inefficient: Observers effectively use only √N objects in their estimates (e...
Purpose. This study investigated the ways in which observers can combine dynamic visual and auditory information. Method. The observer viewed a quick stream of 18 gray disks (83 ms per disk), each accompanied by a simultaneous burst of auditory white noise. Three levels of disk brightness and of noise loudness were used to produce 9 different types...
Cuttlefish, Sepia officinalis, commonly use their visually-guided, rapid adaptive camouflage for multiple tactics to avoid detection or recognition by predators. Two common tactics are background matching and resembling an object (masquerade) in the immediate area. This laboratory study investigated whether cuttlefish preferentially camouflage them...
Adaptation to a moving stimulus changes the perception of a stationary grating and also reduces contrast sensitivity to the adaptor. We determined whether the first effect could be predicted from the second. The contrast discrimination (T vs. C) function for a drifting 7.5 Hz grating test stimulus was determined when observers were adapted to a low...
Three-quarters of a century ago Gestalt psychologist Kurt Koffka described a remarkable effect: when a contiguous gray ring is placed on a background half one shade of gray, half another, the ring appears homogeneous. However, if the ring is divided, the two halves of the ring appear different shades of gray, the half of the ring on the darker back...
Camouflage versatility is probably no better developed in the animal kingdom than in the coleoid cephalopods (octopus, squid, cuttlefish). These marine molluscs possess soft bodies, diverse behaviour, elaborate skin patterning capabilities and a sophisticated visual system that controls body patterning for communication and camouflage (Packard 1995...
Background / Purpose:
This experiment sought to answer the following question: how well can observers combine dynamic visual and auditory information (brightness & loudness) to meet different task demands?For each condition, both participants achieved similar token-type sensitivity functions.
Main conclusion:
Participants were able to selectiv...
Background / Purpose:
This ongoing project asks the question: “Do visual numerosity judgments depend only on the perceptual strength of the difference between targets versus distractors?”If so, then the visual property that makes targets different from distractors should not matter. Specifically, if the perceptual strength of the difference betwe...
Purpose: Milner & Goodale, 1995, propose that visual processing splits into a ventral, "what" stream devoted to conscious recognition processes and a dorsal, "how" stream mediating motor control. Whereas the ventral stream receives input from both the magnocellular and parvocellular pathways, the dorsal stream receives only magnocellular input, sug...
Choice reaction time generally increases linearly with the logarithm of the number of potential stimulus-response alternatives, a regularity known as Hick's law. Two apparent violations of this generalization, which have been reported for aimed eye movements (Kveraga, Boucher, & Hughes, Experimental Brain Research, 146, 307-314, 2002), and arm move...
Purpose. We studied the perceptual segregation of texture pairs consisting of a grid of uniform, square texture elements, differing only in the distribution of intensities across those elements. If two textures differ in mean intensity ("lightness") or in the variance of intensity ("contrast"), then they are easily segregated. Chubb, Econopouly & L...
PURPOSE: Much evidence (due mainly to Durgin & colleagues) shows that human vision is sensitive to the density of elements in sparse displays. Here we investigate the dependence of density judgments on element intensity. METHOD: In Expt. 1, S's viewed a brief display comprising two sparse fields of dots, separated by a central vertical line and jud...
There are 16 extremes of the binary 2x2 block probabilities that allow for maximum-entropy extension. The textures that have zero second-order correlation (purple background) are extreme examples of the textures shown above. Textures with nonzero second-order correlations can be grouped into isodipole families (each background color), within which...
PURPOSE: To dissociate the “where,” “what,” and “how” functions of the visual pathways by showing differential performance among task types. METHODS: Stimuli designed to differentially activate the parvocellular and magnocellular pathways, luminance-defined and equiluminant color-defined targets, were adjusted to be equisalient on an allocentric “w...
Purpose: To analyze the role of irrelevant, visually salient boundaries in the short-term storage of visual information. Method: On each trial, the S viewed two briefly flashed, 6-by-6, random checkerboards separated by a 1 sec. ISI and judged (with feedback) whether they were different. In Exp. 1, the S was aware that the difference (if there was...
In his Correspondence article, Dr Packard questions our approach to studying cuttlefish camouflage body patterning ([Chiao et al., 2010][1]). While we respect Packard's invaluable contribution to the study of cephalopod chromatophores and freely acknowledge that he has inspired us to continue to
How well can observers selectively attend only to dots that are lighter or darker than the background when all dot intensities are present? Observers estimated centroids of briefly flashed, sparse clouds of 8 or 16 dots, ranging in intensity from dark black to bright white on a gray background. Attention instructions were to equally weight: (i) dot...
Judgments of the brightness of a test patch are strongly influenced by contrast and assimilation. However, the experiments that document these effects typically do not use feedback. We wondered whether observers might have access to strategies that were cleansed of these effects if they were given trial-by-trial feedback. In this study, observers v...
The minimum motion method is a standard tool used by psychophysicists obtaining perceptually equiluminant display settings for a light of hue A to another fixed light F. This method uses a 4 frame periodic stimulus, whose 1st and 3rd frames comprise counterphase, achromatic gratings and whose 2nd and 4th frames comprise counterphase square wave gra...
The merest glance is usually sufficient for an observer to get the gist of a scene. That is because the visual system statistically summarizes its input. We are currently exploring the precision and efficiency with which orientation and size statistics can be calculated. Previous work has established that orientation discrimination is limited by an...
This study used texture discrimination tasks to investigate preattentive visual sensitivity to equiluminant chromatic variations. Specifically, we looked for evidence of “half-cardinal-axis” mechanisms in DKL space - i.e., mechanisms sensitive exclusively to variations between neutral gray and each of the red and green poles of the L-M axis and the...
Substantial evidence suggests that observers can accurately estimate the centroid of a spatially extended target. We investigated the top-down attentional control of these mechanisms. Observers estimated (with mouse-clicks) the centroids of briefly flashed, sparse clouds of either 8 or 16 dots of various intensities under three different attentiona...
We wondered whether plaids activate preattentive mechanisms distinct from those activated by their component gratings. Observers searched for a target plaid—the sum of two perpendicular components in a circular window (radius = 0.65 deg). The target was present on half the trials. On target-present trials, approximately half of the three or seven d...
Poirson and colleagues (JOSA A, 7, 783–789, 1990) presented a simple and compelling argument to show that one cannot determine the sensitivity of mechanisms that underlie discrimination performance if thresholds lie on an ellipsoid (and they almost always do, at least within measurement error). In brief, the ellipsoidal model assumes that stimuli p...
Substantial evidence suggests that observers can accurately estimate the centroid of a spatially extended target. We investigated whether these mechanisms could be brought under top-down attentional control. Specifically, we asked observers to estimate (with mouse-clicks) the centroids of briefly flashed, sparse clouds comprising either 8 or 16 dot...
Julesz (1975) famously conjectured that any two textures with identical autocorrelation functions would be indiscriminable. Although various counterexamples have been discovered, new methods for constructing textures with identical space-average autocorrelation functions remain important because they often lead to useful insights about preattentive...
Purpose. To assess the influence of target context on performance in a change detection task. Method. On each trial, the observer viewed two briefly flashed, 6-by-6, random checkerboards separated by a 1 sec. ISI and judged (with feedback) whether they were different. The observer was aware that the difference (if there was one) was always in the c...
