CiteULike: bhamcnil's no-tag

Perceptual-cognitive universals as reflections of the world.

RN Shepard — 2008-08-20T10:36:45-00:00

The Behavioral and brain sciences, Vol. 24, No. 4. (August 2001)

The universality, invariance, and elegance of principles governing the universe may be reflected in principles of the minds that have evolved in that universe--provided that the mental principles are formulated with respect to the abstract spaces appropriate for the representation of biologically significant objects and their properties. (1) Positions and motions of objects conserve their shapes in the geometrically fullest and simplest way when represented as points and connecting geodesic paths in the six-dimensional manifold jointly determined by the Euclidean group of three-dimensional space and the symmetry group of each object. (2) Colors of objects attain constancy when represented as points in a three-dimensional vector space in which each variation in natural illumination is canceled by application of its inverse from the three-dimensional linear group of terrestrial transformations of the invariant solar source. (3) Kinds of objects support optimal generalization and categorization when represented, in an evolutionarily-shaped space of possible objects, as connected regions with associated weights determined by Bayesian revision of maximum-entropy priors.

Perceptual illusion of rotation of three-dimensional objects.

RN Shepard — 2008-08-20T10:28:05-00:00

Science (New York, N.Y.), Vol. 191, No. 4230. (5 March 1976), pp. 952-954.

Perspective views of the same three-dimensional object in two orientations, when presented in alternation, produced an illusion of rigid rotation. The minimum cycle duration required for the illusion increased linearly with the angular difference between the orientations and at the same slope for rotations in depth and in the picture plane.

On the spatial distribution of visual attention.

B Crassini — 2008-08-20T10:22:05-00:00

Journal of experimental psychology. Human perception and performance, Vol. 12, No. 3. (August 1986), pp. 380-382.

An implication of the data analysis and presentation of Podgorny and Shepard (1983) is that subjects are able to attend simultaneously to more than one square of a grid display when the squares are separated by unattended areas: Attention to such nonunitary areas produces similar benefits as attention to unitary areas. These benefits are reflected in reaction times (RTs), which were reported by Podgorny and Shepard (1983) as being related to a measure of spatial dispersion (compactness) of the attended areas, but this measure does not signify whether these areas are unitary or not. A reanalysis of part of Podgorny and Shepard's (1983) data shows that RTs to attended and unattended squares are almost identical when the attended areas are nonunitary. This reanalysis also shows that RTs are related to compactness for unitary attended areas but that this relation breaks down when attention is focused on nonunitary areas. In addition, Podgorny and Shepard's (1983) data are presented in a way that demonstrates the importance of the actual grid location of probes on RTs. The failure of compactness to reflect these aspects of the spatial nature of attention suggests that this metric is deficient when applied to the study of the spatial determinants of attention.

Distribution of visual attention over space.

P Podgorny — 2008-08-20T10:20:17-00:00

Journal of experimental psychology. Human perception and performance, Vol. 9, No. 3. (June 1983), pp. 380-393.

Subjects viewed 3 X 3 grids in which different subsets of the nine squares were designated as "figure," either by physical shading of those squares or by a verbal instruction to imagine those squares as shaded. The time taken by participants to respond "on" or "off" the figure was measured for single or multiple probe dots, which all appeared on or off the figural subset together, and which had already been shown to be equally detectable against shaded or unshaded squares and in all nine locations within the grid. In contrast to the set-size effect generally found in experiments on memory scanning, reaction time did not necessarily increase with the number of squares in the figural subset. Instead, the critical variable, which in previous research may often have adventitiously covaried with set size, was the spatial compactness of the subsets (as indexed by square-root-area over perimeter): Probes of less compact figures required more time to classify correctly. Subjects were evidently more successful in confining their attention to sets of mutually proximal items. Reasons are given for believing that this principle may also apply in the more abstract representational or semantic spaces that determine reaction times and errors in various other cognitive tasks.

Spatial factors in visual attention: a reply to Crassini.

RN Shepard — 2008-08-20T10:18:09-00:00

Journal of experimental psychology. Human perception and performance, Vol. 12, No. 3. (August 1986), pp. 383-387.

Distances between stimuli and, derivatively, compactness of stimulus subsets are pervasive determiners of discrimination and classification performance. Contrary to Crassini (1986), these factors are sufficient to account for the major patterns in the chronometric data of Podgorny and Shepard (1978, 1983). Other factors, such as the dichotomous one distinguishing what Crassini terms unitary and nonunitary subsets, may exert some additional influence. But a convincing demonstration would require formulation of a quantitative model capable of being pitted against the distance-based model of Podgorny and Shepard within the context of their entire body of data.

Psychologically simple motions as geodesic paths II. Symmetric objects

Eloise Carlton — 2008-08-20T10:04:04-00:00

Journal of Mathematical Psychology, Vol. 34, No. 2. (June 1990), pp. 189-228.

The particular spatial transformations that are psychologically favored in real, apparent, or imagined motion may reflect internalizations of principles governing the rigid motions of objects in the three-dimensional world. A preceding article (Part I) focused on the representation of motions of an asymmetric object--an object that cannot be brought into congruence with itself through a rotation of less than 360°. It proposed that the psychologically simplest motions between any two positions of such an object correspond, in the six-dimensional manifold of its possible positions, to geodesic paths, such as those prescribed by (a) the laws of classical physics, (b) the principles of kinematic geometry, or (c) some weighted combination of the two. The present article (Part II) extends the formulation of kinematic geometry to objects possessing or approximating symmetries that permit self-congruence (or near congruence) of the object through rotations between 0 and 360°. Such symmetries give rise to additional geodesic transformations, including (a) screw motions like those prescribed by Chasles's theorem of kinematic geometry, but around additional, symmetry-induced axes in space, or even (b) rotations around an object-centered axis of symmetry that is itself undergoing a screw motion in space. Some previously reported, current, and projected experiments on real, apparent, and imagined motion are considered for the evidence they provide for or against the alternative formulations considered.

Psychologically simple motions as geodesic paths I. Asymmetric objects

Eloise Carlton — 2008-08-20T10:01:29-00:00

Journal of Mathematical Psychology, Vol. 34, No. 2. (June 1990), pp. 127-188.

There are infinitely many ways in which an object might rigidly move between any two positions in space. Experiments on real, apparent, and imagined motion indicate, however, that humans favor particular connecting motions. The favored motions may reflect internalizations of principles governing the transformations of objects in the external world. This first of two articles (Part I) offers formalizations and preliminary evaluations of two primary candidates for principles that may have been internalized: (a) laws of physics--especially the principle of least action, according to which, in the absence of external forces, the center of a rigid body traverses a straight line between any two positions while any rotation is about its rectilinearly translating center--and (b) principles of kinematic geometry--especially Chasles's theorem, according to which, for any two positions of an asymmetric object, there exists a unique axis in space such that the object can be carried from the one position to the other by a helical combination of a translation along and rotation about that axis. A one-parameter family of cases intermediate between the pure cases of physics and geometry is also considered. Each case is abstractly formulated in terms of the straightest transformational path (geodesic) that it prescribes in the six-dimensional manifold of possible positions of the object in space. The corresponding motions are concretely illustrated for asymmetric objects in two- and in three-dimensional space. Characterization of the additional geodesics permitted by objects possessing various symmetries is deferred to a second article (Part II). The formalization of internalized principles and associated geodesics may eventually lead to a mental mechanics governing how humans and other animals interpret events and plan and carry out actions in the world.

Functional representations common to visual perception and imagination.

P Podgorny — 2008-08-20T09:45:23-00:00

Journal of experimental psychology. Human perception and performance, Vol. 4, No. 1. (February 1978), pp. 21-35.

Subjects determined whether probe dots appearing in component squares of a 5 X 5 grid fell on a figure that, depending on the condition, was (a) visually presented as a pattern of darkened squares, (b) only remembered from a preceding presentation of such a pattern, or (c) imaginally generated from a verbal code. The speed and accuracy of the responses to the probes as well as the functional dependencies of the reaction times on structural variables were essentially the same whether the figural pattern was imagined, remembered, or actually seen. Reaction times averaged between 400 and 500 msec and were consistently faster (a) for on-figure than for off-figure responses, (b) for simpler figures that had fewer squares, (c) for off-figure probes that were more distant from the figure, and (d) for on-figure probes that consisted either of more dots on the figure or of a dot at the intersection of a horizontal and a vertical bar. The reults were consistent with a model in which a subject's perceptual or imaginal representations of these forms contain barlike units that respond independently to the probes.

Apparent motion: evidence of the influence of shape, slant, and size on the correspondence process.

A Mack — 2008-08-20T09:42:15-00:00

Perception & psychophysics, Vol. 46, No. 2. (August 1989), pp. 201-206.

Four stimulus elements configured as a notional diamond were flashed in pairs to elicit apparent motion. When the elements were identical (4 Zs), the direction of apparent motion was ambiguous. When the elements were pairs of different letters (Cs and Os, Es and Zs), letters of different sizes (Zs and zs), or oppositely oblique lines, the direction of apparent motion tended to be between identical elements. This was true, however, only for an initial, brief observation period. Subsequently, the direction of apparent motion tended to be determined by the direction of motion perceived at first, regardless of the character of the elements. This quickly established directional set (within 10 sec) largely swamped any tendency to resolve correspondence in terms of a feature of the stimulus. It appears to be based on spatial rather than retinal or egocentric coordinates.

Shape, orientation, and apparent rotational motion.

JE Farrell — 2008-08-20T09:40:56-00:00

Journal of experimental psychology. Human perception and performance, Vol. 7, No. 2. (April 1981), pp. 477-486.

Apparent rotational motion was investigated in polygonal shapes ranging in rotational symmetry from random to self-identical under 180 degrees rotation. Observers adjusted the rate of alternation between two computer-displayed orientations of any given polygon to determine the point of breakdown of perceived rigid rotation between those two orientations. For asymmetric polygons, the minimum stimulus-onset asynchrony yielding apparent rigid rotation increased approximately linearly with orientational disparity, as anticipated on the basis of the extension of Korte's third law to rotational motion by Shepard and Judd. For nearly symmetric polygons, however, the critical time increased markedly as the disparities approached 180 degrees, owing to the availability of a shorter, nonrigid rotation in the opposite direction. The results demonstrate the existence of competing mental tendencies to preserve the rigid structure of an object and to traverse a minimum transformational path.

IN SIGHT, OUT OF MIND:

Daniel Simons — 2008-08-20T09:32:46-00:00

Psychological Science, Vol. 7, No. 5. (1996), pp. 301-305.

Models of human visual memory often presuppose an extraordinary ability to recognize and identify objects, based on evidence for nearly flawless recognition of hundreds or even thousands of pictures after a single presentation. (Ntckerson, 1965, Shepard, 1967, Standing, Conezto, & Haber, 1970) and for storage of tens of thousands of object representations over the course of a lifetime (Biederman, 1987). However, recent evidence suggests that observers often fail to notice dramatic changes occurring during eye movements (e g., Grimes, 1996). The experiments presented here show that immediate memory for object identity is surprisingly poor, especially when verbal labeling is prevented However, memory for the spatial configuration of objects remains excellent even with verbal interferes e suggesting a fundamental difference between representations of spatial configuration and object properties.

Failure to detect changes to attended objects in motion pictures

DT Levin — 2008-08-20T09:31:51-00:00

Psychonomic Bulletin and Review, Vol. 4, No. 4. (1997), pp. 501-506.

Change blindness

Daniel Simons — 2008-08-20T09:26:45-00:00

Trends in Cognitive Sciences, Vol. 1, No. 7. (October 1997), pp. 261-267.

Although at any instant we experience a rich, detailed visual world, we do not use such visual details to form a stable representation across views. Over the past five years, researchers have focused increasingly on [`]change blindness' (the inability to detect changes to an object or scene) as a means to examine the nature of our representations. Experiments using a diverse range of methods and displays have produced strikingly similar results: unless a change to a visual scene produces a localizable change or transient at a specific position on the retina, generally, people will not detect it. We review theory and research motivating work on change blindness and discuss recent evidence that people are blind to changes occurring in photographs, in motion pictures and even in real-world interactions. These findings suggest that relatively little visual information is preserved from one view to the next, and question a fundamental assumption that has underlain perception research for centuries: namely, that we need to store a detailed visual representation in the mind/brain from one view to the next.

Perceiving Real-World Viewpoint Changes

Daniel Simons — 2008-08-20T09:24:38-00:00

Psychological Science, Vol. 9, No. 4. (1998), pp. 315-320.

Retinal images vary as observers move through the environment, but observers seem to have little difficulty recognizing objects and scenes across changes in view. Although real-world view changes can be produced both by object rotations (orientation changes) and by observer movements (viewpoint changes), research on recognition across views has relied exclusively on display rotations. However, research on spatial reasoning suggests a possible dissociation between orientation and viewpoint. Here we demonstrate that scene recognition in the real world depends on more than the retinal projection of the visible array; viewpoint changes have little effect on detection of layout changes, but equivalent orientation changes disrupt performance significantly. Findings from our three experiments suggest that scene recognition across view changes relies on a mechanism that updates a viewer-centered representation during observer movements, a mechanism not available for orientation changes. These results link findings from spatial tasks to work on object and scene recognition and highlight the importance of considering the mechanisms underlying recognition in real environments.

Visual representations during saccadic eye movements.

T Moore — 2008-05-23T14:06:46-00:00

Proceedings of the National Academy of Sciences of the United States of America, Vol. 95, No. 15. (21 July 1998), pp. 8981-8984.

In normal vision, shifts of attention are usually followed by saccadic eye movements. Neurons in extrastriate area V4 are modulated by focal attention when eye movements are withheld, but they also respond in advance of visually guided saccadic eye movements. We have examined the visual selectivity of saccade-related responses of area V4 neurons in monkeys making delayed eye movements to receptive field stimuli of varying orientation. This task did not require the monkey to attend to orientation per se but merely to foveate the receptive field stimulus. We present evidence that the presaccadic enhancement exhibited by V4 neurons, quite separate from the response at stimulus onset, is a resurgent visual representation that seems as selective as the response is when the stimulus first appears. The presaccadic enhancement appears to provide a strengthening of a decaying featural representation immediately before an eye movement is directed to visual targets. We suggest that this reactivation provides a mechanism by which a clear perception of the saccade goal can be maintained during the execution of the saccade, perhaps for the purpose of establishing continuity across eye movements.

Spatial heterogeneity of inhibitory surrounds in the middle temporal visual area.

DK Xiao — 2008-05-14T14:50:09-00:00

Proceedings of the National Academy of Sciences of the United States of America, Vol. 92, No. 24. (21 November 1995), pp. 11303-11306.

A recurrent theme in the organization of vertebrate visual cortex is that of receptive fields with an associated "silent" opponency component. In the middle temporal area (area MT), a cortical visual area involved in the analysis of retinal motion in primates, this opponency appears in the form of a region outside the classical receptive field (CRF) that in itself gives no response but suppresses responses to motion evoked within the CRF. This antagonistic motion surround has been described as very large and symmetrically arrayed around the CRF. On the basis of this view, the primary function of the surround has long been thought to consist of simple figure-ground segregation based on movement. We have made use of small stimulus patches to map the form and extent of the surround and find evidence that the surround inhibition of many MT cells is in fact confined to restricted regions on one side or on opposite sides of the CRF. Such regions endow MT cells with the ability to make local-to-local motion comparisons, capable of extracting more complex features from the visual environment, and as such, may be better viewed as intrinsic parts of the receptive field, rather than as separate entities responsible for local-to-global comparisons.

Parallel pathways in the visual system: their role in perception at isoluminance.

PH Schiller — 2008-08-20T09:08:41-00:00

Neuropsychologia, Vol. 29, No. 6. (1991), pp. 433-441.

It has been proposed that the functions of the two major parallel channels of the primate visual system, the color-opponent and the broad-band, can be determined in psychophysical experiments by eliminating luminance but maintaining chrominance information (isoluminance), since under such conditions the broad-band channel is believed to be silenced. To test this proposition we examined the visual functions of monkeys after blocking either of these channels and we also assessed the responses of neurons to isoluminant stimuli in the lateral geniculate nucleus. We show that color, texture, stereopsis and pattern perception in the absence of the color-opponent channel, and flicker and motion perception in the absence of the broad-band channel are compromised. Yet isoluminance functions for stereopsis and texture in the absence of the broad-band channel and for motion in the absence of the color-opponent channel are indistinguishable from normal. Our recordings show that the neuronal responses of the broad-band cells for isoluminant exchange of red and green lights are reduced but not eliminated and that the color-opponent cells also become similarly less responsive under these conditions. We conclude that perceptual losses at isoluminance are not specific for either channel.

Two attentional deficits in serial target search: the visual attentional blink and an amodal task-switch deficit.

MC Potter — 2008-08-20T09:00:49-00:00

Journal of experimental psychology. Learning, memory, and cognition, Vol. 24, No. 4. (July 1998), pp. 979-992.

When monitoring a rapid serial visual presentation at 100 ms per item for 2 targets among distractors, viewers have difficulty reporting the 2nd target (T2) when it appears 200-500 ms after the onset of the 1st letter target (T1): an attentional blink (AB; M. M. Chun & M. C. Potter, 1995b; J. E. Raymond, K. L. Shapiro, & K. M. Arnell, 1992). Does the same deficit occur with auditory search? The authors compared search for auditory, visual, and cross-modal targets in 2 tasks: (a) identifying 2 target letters among digits (Experiments 1-3 and 5) or digits among letters (Experiment 6), and (b) identifying 1 digit among letters and deciding whether an X occurred among the subsequent letters (Experiment 4). In the experiments using the 1st task, the standard AB was found only when both targets were visual. In the 2nd task, with a change in selective set from T1 to T2, a task-switching deficit was obtained regardless of target modality.

Temporary suppression of visual processing in an RSVP task: an attentional blink? .

JE Raymond — 2006-12-11T22:22:19-00:00

J Exp Psychol Hum Percept Perform, Vol. 18, No. 3. (August 1992), pp. 849-860.

Through rapid serial visual presentation (RSVP), we asked Ss to identify a partially specified letter (target) and then to detect the presence or absence of a fully specified letter (probe). Whereas targets are accurately identified, probes are poorly detected when they are presented during a 270-ms interval beginning 180 ms after the target. Probes presented immediately after the target or later in the RSVP stream are accurately detected. This temporary reduction in probe detection was not found in conditions in which a brief blank interval followed the target or Ss were not required to identify the target. The data suggest that the presentation of stimuli after the target but before target-identification processes are complete produces interference at a letter-recognition stage. This interference may cause the temporary suppression of visual attention mechanisms observed in the present study.

Attention to visual pattern information produces the attentional blink in rapid serial visual presentation.

KL Shapiro — 2008-08-20T08:56:22-00:00

Journal of experimental psychology. Human perception and performance, Vol. 20, No. 2. (April 1994), pp. 357-371.

To-investigate the temporal allocation of attention, a series of 7 experiments using rapid serial visual presentation (RSVP) was designed to examine the relationship of the attentional demands of various target tasks to the production of the subsequent visual attentional deficit, or "attentional blink" (AB), recently reported by J. E. Raymond, K. L. Shapiro, and K. M. Arnell (1992). The principal finding is that AB occurs only when a target is an object and does not occur when the target is defined by a temporal interval. Target detection difficulty as estimated by d' analysis reveals no relationship between the attentional demands of the target and the production of the AB. A late-selection account of this phenomenon is offered in place of the early-selection account advanced in Raymond et al.'s previous report.

Priming reveals attentional modulation of human motion sensitivity.

JE Raymond — 2008-08-20T08:51:51-00:00

Vision research, Vol. 38, No. 19. (October 1998), pp. 2863-2867.

Although recent fMRI and single unit recording studies have shown that attention modulates neural activity in motion sensitive areas of extrastriate cortex, these approaches cannot reveal qualitative or quantitative effects of attention on perception of motion. To investigate this, we asked observers to select one of two orthogonal directions in a brief, transparent dot display (prime) and then measured their sensitivity to global directional motion in a second uni-directional dot display (probe) presented a short time later. When probe direction matched the attended prime direction, sensitivity was degraded. But, when probe direction matched the ignored prime direction, sensitivity was enhanced, even though both components were of equal physical strength. Sensitivity was unchanged for directions opposite to either previously seen direction. Neither sensory adaptation nor opponent direction mechanisms can account for these data. Rather, processes initiated by visual selection must underlie these dramatic changes in motion sensitivity.

Successive episodes produce direction contrast effects in motion perception.

JE Raymond — 2008-08-20T08:48:19-00:00

Vision research, Vol. 38, No. 4. (February 1998), pp. 579-589.

Motion coherence thresholds decline with an increase in the number of frames in a random dot kinematogram (RDK), indicating that motion information can be integrated across successive frames. We investigated whether such temporal integration would be disrupted by a brief interval (32-600 msec) inserted into a motion sequence, perceptually dividing it into two successive episodes. Both episodes consisted of only a few frames (between 3 and 15), with the first episode being 100% coherent and the coherence of the second episode being adjusted to determine threshold. In four experiments we observed that coherence threshold for motion in the second episode was elevated if the directions in the two episodes matched, was lowered if they were opposite, and was unaffected if they were orthogonal. This successive direction contrast effect did not vary with the duration of the interval, suggesting that it is not an adaptation effect. The result of varying the number of frames in the second episode suggests that these effects are not due to alterations in cooperative activity among motion detectors. We suggest that successive direction contrast effects may reflect activity of higher-order perceptual organization mechanisms.

Attentional modulation of visual motion perception.

JE Raymond — 2008-08-20T08:47:28-00:00

Trends in cognitive sciences, Vol. 4, No. 2. (February 2000), pp. 42-50.

How is the perception and processing of visual motion affected by attention? This review examines recent research in cognition, perception and neurophysiology that explores how ongoing behavioural tasks (and the attentional states they impose) modulate the processing of visual motion. Although traditional views hold that motion is processed in an obligatory, 'pre-attentive' manner, evidence for processing in a task-independent manner is scant. Recent studies of human perception that have measured motion priming, motion aftereffects, uncertainty effects, and motion-interaction effects indicate instead that even simple aspects of motion processing may be substantially affected by whether motion information in a task is used or ignored by the perceiver. Single-unit studies in brain areas sensitive to visual motion in monkeys, and functional imaging studies on humans, also indicate that task and attentional state affect activity levels in brain regions thought to be important in motion perception. This review brings together these converging findings of attentional modulation of motion perception and considers them in light of object-oriented theories of attention.

Selectivity for polar, hyperbolic, and Cartesian gratings in macaque visual cortex.

JL Gallant — 2006-01-30T19:40:33-00:00

Science, Vol. 259, No. 5091. (1 January 1993), pp. 100-103.

The neural basis of pattern recognition is a central problem in visual neuroscience. Responses of single cells were recorded in area V4 of macaque monkey to three classes of periodic stimuli that are based on spatial derivative operators: polar (concentric and radial), hyperbolic, and conventional sinusoidal (Cartesian) gratings. Of 118 cells tested, 16 percent responded significantly more to polar or hyperbolic (non-Cartesian) gratings than to Cartesian gratings and only 8 percent showed a significant preference for Cartesian gratings. Among cells selective for non-Cartesian gratings, those that preferred concentric gratings were most common. Cells selective for non-Cartesian gratings may constitute an important intermediate stage in pattern recognition and the representation of surface shape.

The attentional blink

KL Shapiro — 2008-08-20T08:44:11-00:00

Trends in Cognitive Sciences, Vol. 1, No. 8. (November 1997), pp. 291-296.

When two masked targets (T1 and T2) are presented within approximately 500 ms of each other, subjects are often unable to report the second of the two targets (T2) accurately, even though the first has been reported correctly. In contrast, subjects can report T2 accurately when instructed to ignore T1, or when T1 and T2 are separated by more than 500 ms. The above pattern of results has been labelled the attentional blink (AB). Experiments have revealed that the AB is not the result of perceptual, memory or response output limitations. In general, the various theories advanced to account for the AB, although they differ in the specific mechanisms purported to be responsible, assume that allocating attention to T1 leaves less attention for T2, rendering T2 vulnerable to decay or substitution. The present report attempts to bring together these various accounts by proposing a unifying theory. This report also highlights recent attempts to determine if the AB exists across stimulus modalities and points to applications of AB methods in understanding deficits of visual neglect. We conclude by suggesting that investigations of the AB argue in favour of the view that attention may be thought of as a necessary (but not sufficient) condition for enabling consciousness.

PRIMING FROM THE ATTENTIONAL BLINK:

Kimron Shapiro — 2008-08-20T08:40:38-00:00

Psychological Science, Vol. 8, No. 2. (1997), pp. 95-100.

2014When people must detect several targets in a very rapid stream of successive visual events at the same location, detection of an initial target induces misses for subsequent targets within a brief period. This attentional blink may serve to prevent interruption of ongoing target processing by temporarily suppressing vision for subsequent stimuli. We examined the level at which the internal blink operates, specifically, whether it prevents early visual processing or prevents quite substantial processing from reaching awareness. Our data support the latter view. We observed priming from missed letter targets, benefiting detection of a subsequent target with the same identity but a different case. In a second study, we observed semantic priming from word targets that were missed during the blink. These results demonstrate that attentional gating within the blink operates only after substantial stimulus processing has already taken place. The results are discussed in terms of two forms of visual representation, namely, types and tokens.

Mapping of contralateral space in retinotopic coordinates by a parietal cortical area in humans.

MI Sereno — 2005-02-04T22:08:21-00:00

Science, Vol. 294, No. 5545. (9 November 2001), pp. 1350-1354.

The internal organization of a higher level visual area in the human parietal cortex was mapped. Functional magnetic resonance images were acquired while the polar angle of a peripheral target for a delayed saccade was gradually changed. A region in the superior parietal cortex showed robust retinotopic mapping of the remembered target angle. The map reversed when the direction of rotation of the remembered targets was reversed and persisted unchanged when study participants detected rare target reappearances while maintaining fixation, or when the eccentricity of successive remembered targets was unpredictable. This region may correspond to the lateral intraparietal area in macaque monkeys.

Brain mapping in animals and humans.

MI Sereno — 2008-08-20T08:34:09-00:00

Current opinion in neurobiology, Vol. 8, No. 2. (April 1998), pp. 188-194.

Studies using functional magnetic resonance imaging (fMRI) to map cortical areas in humans have revealed many similarities with recent cortical mapping studies from nonhuman primates as well as some striking differences. Improved methods for analyzing, displaying and averaging fMRI data on an unfolded cortical surface atlas are poised to improve the integration of information across burgeoning numbers of imaging studies. By combining fMRI with electrical and passive magnetic imaging modalities, the millisecond-to-millisecond sequence of activation of different cortical regions elicited by an event can be imaged, provided the regions are sufficiently far apart.

Brain regions associated with retrieval of structurally coherent visual information.

DL Schacter — 2008-08-20T08:32:25-00:00

Nature, Vol. 376, No. 6541. (17 August 1995), pp. 587-590.

An object's global, three-dimensional structure may be represented by a specialized brain system involving regions of inferior temporal cortex. This system's role in object representation can be understood by experiments in which people study drawings of novel objects with possible or impossible three-dimensional structures, and later make either possible/impossible object decisions or old/new recognition decisions about briefly flashed studied and non-studied objects. Although object decisions about possible objects are facilitated by prior study, there is no corresponding facilitation for impossible objects, thereby implicating a system that is specifically involved in the representation of structurally coherent visual objects. Here we show, by positron emission tomography (PET), that increases in blood flow in inferior temporal regions are associated with object decisions about possible but not impossible objects, and that there are increases in the vicinity of the hippocampal formation associated with episodic recognition of possible objects.

Implicit memory: a selective review.

DL Schacter — 2007-05-09T20:10:33-00:00

Annu Rev Neurosci, Vol. 16 (1993), pp. 159-182.

Perceptual specificity of auditory priming: implicit memory for voice intonation and fundamental frequency.

BA Church — 2008-08-20T08:27:02-00:00

Journal of experimental psychology. Learning, memory, and cognition, Vol. 20, No. 3. (May 1994), pp. 521-533.

Five experiments explored the effect of acoustic changes between study and test on implicit and explicit memory for spoken words. Study-test changes in the speaker's voice, intonation, and fundamental frequency produced significant impairments of auditory priming on implicit tests of auditory identification and stem completion but had little or no effect on explicit recall and recognition tests (Experiments 1-4). However, study-test changes in overall decibel level had no effect on priming on an auditory stem-completion test or on cued-recall performance (Experiment 5). The results are consistent with the idea that fundamental frequency information is represented in a perceptual representation system that plays an important role in auditory priming.

IMPLICIT MEMORY IN AMNESIC PATIENTS:

Daniel Schacter — 2008-08-20T08:25:08-00:00

Psychological Science, Vol. 6, No. 1. (1995), pp. 20-25.

Amnesic patients generally exhibit spared priming effects on implicit memory tasks despite poor explicit memory In a previous study, we demonstrated normal auditory priming in amnesic patients on an identification-in-noise test in which the magnitude of priming is independent of whether the speaker's voice is the same or different at study and test In the present experiment, we examined auditory priming on a filter identification test in which the magnitude of priming in control subjects is higher when the speaker's voice is the same at study and test than when it is different Amnesic patients, by contrast, failed to exhibit more priming in a same-voice condition than in a different-voice condition Voice-specific priming may depend on a memory system that is impaired in amnesia

Priming impossible figures in the object decision test: The critical importance of perceived stimulus complexity.

M Carrasco — 2008-08-20T08:14:50-00:00

Psychonomic Bulletin and Review, Vol. 3, No. 3. (1996), pp. 344-351.

The predictive brain: temporal coincidence and temporal order in synaptic learning mechanisms.

PR Montague — 2008-08-19T15:59:58-00:00

Learning & memory (Cold Spring Harbor, N.Y.), Vol. 1, No. 1. (n 1994), pp. 1-33.

Some forms of synaptic plasticity depend on the temporal coincidence of presynaptic activity and postsynaptic response. This requirement is consistent with the Hebbian, or correlational, type of learning rule used in many neural network models. Recent evidence suggests that synaptic plasticity may depend in part on the production of a membrane permeant-diffusible signal so that spatial volume may also be involved in correlational learning rules. This latter form of synaptic change has been called volume learning. In both Hebbian and volume learning rules, interaction among synaptic inputs depends on the degree of coincidence of the inputs and is otherwise insensitive to their exact temporal order. Conditioning experiments and psychophysical studies have shown, however, that most animals are highly sensitive to the temporal order of the sensory inputs. Although these experiments assay the behavior of the entire animal or perceptual system, they raise the possibility that nervous systems may be sensitive to temporally ordered events at many spatial and temporal scales. We suggest here the existence of a new class of learning rule, called a predictive Hebbian learning rule, that is sensitive to the temporal ordering of synaptic inputs. We show how this predictive learning rule could act at single synaptic connections and through diffuse neuromodulatory systems.

Perspectives on cognitive neuroscience.

PS Churchland — 2008-08-19T15:59:14-00:00

Science (New York, N.Y.), Vol. 242, No. 4879. (4 November 1988), pp. 741-745.

How is it that we can perceive, learn and be aware of the world? The development of new techniques for studying large-scale brain activity, together with insights from computational modeling and a better understanding of cognitive processes, have opened the door for collaborative research that could lead to major advances in our understanding of ourselves.

Induction of synaptic plasticity by Hebbian covariance in the Hippocampus

Terrence Sejnowski — 2008-08-19T15:56:39-00:00

(1989), pp. 105-124.

Filter selection model for motion segmentation and velocity integration

Steven Nowlan — 2008-08-19T15:55:07-00:00

J. Opt. Soc. Am. A, Vol. 11, No. 12. (1 December 1994), pp. 3177-3200.

We present a new approach to computing from image sequences the two-dimensional velocities of moving objects that are occluded and transparent. The new motion model does not attempt to provide an accurate representation of the velocity flow field at fine resolutions but coarsely segments an image into regions of coherent motion, provides an estimate of velocity in each region, and actively selects the most reliable estimates. The model uses motion-energy filters in the first stage of processing and computes, in parallel, two different sets of retinotopically organized spatial arrays of unit responses: one set of units estimates the local velocity, and the second set selects from these local estimates those that support global velocities. Only the subset of local-velocity measurements that are the most reliable is included in estimation of the velocity of objects. The model is in agreement with many of the constraints imposed by the physiological response properties of cells in primate visual cortex, and its performance is similar to that of primates on motion transparency.

LOCAL AND GLOBAL PROCESSES IN VISUAL COMPLETION

Allison Sekuler — 2008-08-19T15:42:04-00:00

Psychological Science, Vol. 5, No. 5. (1994), pp. 260-267.

In the natural environment, objects are frequently occluded, and people continuously complete partly occluded objects Do local processes or global processes control the completion of partly occluded objects? To answer this question, most previous studies simply asked subjects to draw the completions they "saw" Such drawing tasks are highly subjective, and they provide equivocal results Our studies are the first to use an objective, implicit paradigm (primed matching) to determine the extent to which local or global processes underlie the visual completion of partly occluded objects Our results suggest that global processes dominate perceptual completion, whereas local processes do not play a large role Therefore, local theories of completion, or theories in which local processes dominate, cannot be entirely correct

Amodal completion of partly occluded surfaces: is there a mosaic stage?

N Bruno — 2008-08-19T15:40:38-00:00

Journal of experimental psychology. Human perception and performance, Vol. 23, No. 5. (October 1997), pp. 1412-1426.

Recent investigators have proposed that amodal completion is a sequential process requiring a preliminary mosaic stage. Results of 6 studies of the time course of completion processes show support for this mosaic-first view with pictorial displays, but not with displays involving occlusion specified by binocular parallax or when pictorial displays were observed monocularly. These results still do not rule out the mosaic-first view. A parallel model, however, can account more economically for the available data.

Perception of partly occluded objects : a microgenetic analysis

AB Sekuler — 2008-08-19T15:35:33-00:00

Journal of Experimental Psychology: General, Vol. 121, No. 1. (1992), pp. 95-111.

Mutual repulsion between moving visual targets.

W Marshak — 2008-08-19T15:20:43-00:00

Science (New York, N.Y.), Vol. 205, No. 4413. (28 September 1979), pp. 1399-1401.

When two spatially intermingled sets of random dots move in different directions, the direction of each set may be misperceived. Observers report that each set of dots appears to move in a direction displaced by as much as 20 degrees from the direction of its companion set. Probably the result of inhibitory interactions, this mutual repulsion occurs at a central site in the visual system and may normally enhance discrimination of direction.

Motion Perception as a Partnership: Exogenous and Endogenous Contributions

Robert Sekuler — 2008-08-19T15:14:45-00:00

Current Directions in Psychological Science, Vol. 4, No. 2. (1995), pp. 43-47.

Direction perception in complex dynamic displays: the integration of direction information.

SN Watamaniuk — 2008-08-19T15:13:09-00:00

Vision research, Vol. 29, No. 1. (1989), pp. 47-59.

We created random-dot cinematograms in which each dot's successive movements were independently drawn from a Gaussian distribution of directions of some characteristic bandwidth. Such a display, comprising many different, spatially intermingled local motion vectors, can produce a percept of global coherent motion in a single direction. Using pairs of cinematograms, direction discrimination of global motion was measured under various conditions of direction distribution bandwidth, exposure duration, and constancy of each dot's path. A line-element model gave an excellent account of the results: (i) over a considerable range, discrimination was unaffected by the cinematogram's direction distribution bandwidth; (ii) only for the briefest presentations did changes in duration have an effect; (iii) so long as the overall directional content of the cinematogram remained unchanged, the constancy or randomness of individual dots' paths did not affect discrimination. Finally, the line-element model continued to give a good account of the results when we made additional measurements with uniform rather than Gaussian distributions of directions.

Temporal and spatial integration in dynamic random-dot stimuli.

SN Watamaniuk — 2008-08-19T15:06:41-00:00

Vision research, Vol. 32, No. 12. (December 1992), pp. 2341-2347.

Random-dot cinematograms comprising many different, spatially intermingled local motion vectors can produce a percept of global coherent motion in a single direction. Thresholds for discriminating the direction of global motion were measured under various conditions. Discrimination thresholds increased with the width of the distribution of directions in the cinematogram. Thresholds decreased as the duration of area of the cinematogram increased. Temporal integration for global direction discrimination extends over about 465 msec (9.3 frames) while the spatial integration limit is at least as large as 63 deg2 (circular aperture diameter = 9 deg). The large spatial integration area is consistent with the physiology of higher visual areas such as MT and MST.

Detection of changes in speed and direction of motion: reaction time analysis.

EN Dzhafarov — 2008-08-19T15:02:53-00:00

Perception & psychophysics, Vol. 54, No. 6. (December 1993), pp. 733-750.

Observers reacted to the change in the movement of a random-dot field whose initial velocity, V0, was constant for a random period and then switched abruptly to another value, V1. The two movements, both horizontally oriented, were either in the same direction (speed increments or decrements), or in the opposite direction but equal in speed (direction reversals). One of the two velocities, V0 or V1, could be zero (motion onset and offset, respectively). In the range of speeds used, 0-16 deg/sec (dps), the mean reaction time (MRT) for a given value of V0 depended on magnitude of V1-V0 only: MRT approximately r+c(V0)/magnitude of V1-V0 beta, where beta = 2/3, r is a velocity-independent component of MRT, and c(V0) is a parameter whose value is constant for low values of V0 (0-4 dps), and increases beginning with some value of V0 between 4 and 8 dps. These and other data reviewed in the paper are accounted for by a model in which the time-position function of a moving target is encoded by mass activation of a network of Reichardt-type encoders. Motion-onset detection (V0 = 0) is achieved by weighted temporal summation of the outputs of this network, the weights assigned to activated encoders being proportional to their squared spatial spans. By means of a "subtractive normalization," the visual system effectively reduces the detection of velocity changes (a change from V0 to V1) to the detection of motion onset (a change from 0 to V1-V0). Subtractive normalization operates by readjustment of weights: the weights of all encoders are amplified or attenuated depending on their spatial spans, temporal spans, and the initial velocity V0. Assignment of weights and weighted temporal summation are thought of as special-purpose computations performed on the dynamic array of activations in the motion-encoding network, without affecting the activations themselves.

Categorization creates functional features

PG Schyns — 2006-09-08T19:02:31-00:00

Journal of Experimental Psychology: Learning, Memory, and Cognition, Vol. 23, No. 3. (1997), 681.

The use of visual information in natural scenes

Maxine Mccotter — 2007-01-10T07:48:06-00:00

pp. 938-953.

Despite the complexity and diversity of natural scenes, humans are very fast and accurate at identifying basic-level scene categories. In this paper we develop a new technique (based on Bubbles , Gosselin & Schyns, 2001a; Schyns, Bonnar, & Gosselin, 2002) to determine some of the information requirements of basic-level scene categorizations. Using 2400 scenes from an established scene database (Oliva & Torralba, 2001), the algorithm randomly samples the Fourier coefficients of the phase spectrum. Sampled Fourier coefficients retain their original phase while the phase of nonsampled coefficients is replaced with that of white noise. Observers categorized the stimuli into 8 basic-level categories. The location of the sampled Fourier coefficients leading to correct categorizations was recorded per trial. Statistical analyses revealed the major scales and orientations of the phase spectrum that observers used to distinguish scene categories.

The development of features in object concepts.

PG Schyns — 2008-07-18T13:50:59-00:00

The Behavioral and brain sciences, Vol. 21, No. 1. (February 1998)

According to one productive and influential approach to cognition, categorization, object recognition, and higher level cognitive processes operate on a set of fixed features, which are the output of lower level perceptual processes. In many situations, however, it is the higher level cognitive process being executed that influences the lower level features that are created. Rather than viewing the repertoire of features as being fixed by low-level processes, we present a theory in which people create features to subserve the representation and categorization of objects. Two types of category learning should be distinguished. Fixed space category learning occurs when new categorizations are representable with the available feature set. Flexible space category learning occurs when new categorizations cannot be represented with the features available. Whether fixed or flexible, learning depends on the featural contrasts and similarities between the new category to be represented and the individuals existing concepts. Fixed feature approaches face one of two problems with tasks that call for new features: If the fixed features are fairly high level and directly useful for categorization, then they will not be flexible enough to represent all objects that might be relevant for a new task. If the fixed features are small, subsymbolic fragments (such as pixels), then regularities at the level of the functional features required to accomplish categorizations will not be captured by these primitives. We present evidence of flexible perceptual changes arising from category learning and theoretical arguments for the importance of this flexibility. We describe conditions that promote feature creation and argue against interpreting them in terms of fixed features. Finally, we discuss the implications of functional features for object categorization, conceptual development, chunking, constructive induction, and formal models of dimensionality reduction.

Usage of spatial scales for the categorization of faces, objects, and scenes.

DJ Morrison — 2008-07-18T13:49:35-00:00

Psychonomic bulletin & review, Vol. 8, No. 3. (September 2001), pp. 454-469.

The role of spatial scales (or spatial frequencies) in the processing of faces, objects, and scenes has recently seen a surge of research activity. In this review, we will critically examine two main theories of scale usage. The fixed theory proposes that spatial scales are used in a fixed, perceptually determined order (coarse to fine). The flexible theory suggests instead that usage of spatial scales is flexible, depending on the requirements of visual information for the categorization task at hand. The implications of the theories are examined for face, object, and scene categorization, attention, perception, and representation.

Diagnostic recognition: task constraints, object information, and their interactions.

PG Schyns — 2008-07-18T11:44:58-00:00

Cognition, Vol. 67, No. 1-2. (July 1998), pp. 147-179.

Object recognition and categorization research are both concerned with understanding how input information matches object information in memory. It is therefore surprising that these two fields have evolved independently, without much cross-fertilization. It is the main objective of this paper to lay out the basis of a dialogue between object recognition and categorization research, with the hope of raising issues that could cross-fertilize both domains. To this end, the paper develops diagnostic recognition, a framework which formulates recognition performance as an interaction of task constraints and object information. I argue and present examples suggesting that diagnostic recognition could be fruitfully applied to the understanding of everyday object recognition. Issues are raised regarding the psychological status of the interactions specified in the framework.