Bruce Bridgeman

University of California, Santa Cruz | UCSC · Department of Psychology

Several studies have shown that slopes of hills are greatly overestimated. We have recently demonstrated that the overestimates increase logarithmically as the end point of the domain to be estimated increases - every doubling of the distance to the end point results in a constant increment in perceived slope. A theoretical analysis showed that a c...

Several studies have shown that slopes of hills are greatly overestimated. We have recently demonstrated that the overestimates increase logarithmically as the end point of the domain to be estimated is increased. A theoretical analysis showed that a critical parameter is the angle between the observer's line of sight and the slope of the hill, whe...

The slopes of hills tend to be greatly overestimated. Previous studies have found that slope estimates are significantly greater when estimated verbally than with a proprioceptive measure. It has yet to be determined whether these estimates are made for the entire extent of the slope, or whether the estimates in closest proximity are estimated usin...

The ability to read emotional information from a face has clear evolutionary advantages for social animals. Recent research shows that humans have a gaze bias towards the left side of a face image (the right side of the face), and this bias might be controlled by the emotional content of the face. This might be due to more emotional expression on t...

Microsaccade rates and directions were monitored while observers performed a visual working memory task at varying retinal eccentricities. We show that microsaccades generate no interference in a working memory task, indicating that spatial working memory is at least partially insulated from oculomotor activity. Intervening tasks during the memory...

Tossing a marble into a hole changes memory of the hole’s size; it seems larger if the toss was successful than if it was unsuccessful. This has been attributed to the effect of action on subsequent perception or memory. We ask what the action provides: Is it feedback from the motor act or only the information provided by the action that alters mem...

The sensory cortex has been interpreted as coding information rather than stimulus properties since Sokolov in 1960 showed increased response to an unexpected stimulus decrement. The motor cortex is also organized around expectation, coding the goal of an act rather than a set of muscle movements. Expectation drives not only immediate responses but...

We investigated the physiological mechanism of grapheme-color synesthesia using metacontrast masking. A metacontrast target is rendered invisible by a mask that is delayed by about 60 ms; the target and mask do not overlap in space or time. Little masking occurs, however, if the target and mask are simultaneous. This effect must be cortical, becaus...

Observers performed working memory tasks at varying retinal eccentricities, fixating centrally while microsaccade rates and directions were monitored. We show that microsaccades generate no interference in a working memory task, indicating that spatial working memory is at least partially insulated from oculomotor activity. Intervening tasks during...

An exciting new line of research that investigates the impact of one's own hands on visual perception and attention has flourished in the past several years. Specifically, several studies have demonstrated that the nearness of one's hands can modulate visual perception, visual attention, and even visual memory. These studies together shed new light...

Most experiments on attention use impoverished stimuli – disembodied letters, numbers or simple shapes displayed on a blank background - ignoring the possible influence a richly detailed scene might have on attentional processes. In our study photographs of objects were set within a contextually relevant background. Participants used covert attenti...

Current literature maintains that success or failure in the performance of an action can modify perception of the objects of that action. The tests of that modification, however, may have measured memory rather than perception. To address this issue, the current experiment had observers throw a marble into various sized holes and assess their size...

Space constancy, the perception that the visual world remains stable despite the fact that all visual information arrives through retinas that are in continuous motion, has historically been explained by an 'efference copy' of eye innervation that is subtracted from retinal image shifts. Quantitative work has found the efference copy to be too smal...

Observers are known to overestimate the slopes of hills, and estimates of slope are significantly greater when estimated verbally than with a proprioceptive measure. Since neurons in the premotor cortex have been found to respond differently to objects within arm's reach, we hypothesized that slope estimations might show a break where distances are...

Background / Purpose: Perceiving dynamic scenes requires perceptual, attentional, and cognitive processes that generate the impression of real-world motion. Motion can be perceived if two objects are shown at different positions in the visual field. While this is called beta movement the phi-phenomenon represents a special case where the viewer s...

While motor performance can modify perception (Witt & Proffitt, 2005; Witt, Linkenauger, Backdash, & Proffitt, 2008), the time course of this change remains unclear because previous experiments have assessed perception only after the experimental action has occurred. To address this issue, we had participants throw a ball into various sized holes a...

We present two experiments that examine sensory processing during conditions of inattentional blindness. A large rectangular frame that normally induces a Roelofs effect can go unreported due to inattentional blindness. Even when participants fail to report the frame, they mislocalize an attended target in a way consistent with having processed the...

Microsaccades, small saccadic eye movements made during fixation, might accompany shifts of visual attention, serve to refresh the retinal image, or have some other function. We tested the relative importance of these functions by recording exploratory saccades and microsaccades with a free head during a lane-change task in a simulated driving envi...

Abstract Evolutionary theory indicates that consciousness has a function, if it is complex enough to be supported by genetically guided brain structures. Otherwise there would be no selective pressure against degrading it. Hints about its function come from word priming studies, where conscious awareness of a prime allows it to be avoided according...

Perception is interpreted as a set of capabilities that facilitate two functions necessary for survival; learning about the environment and controlling real-time behavioral interactions with it. Perceptual capabilities evolve in the context of an organism and its environment, adapted to an organism's ecological niche. The relation between embodied...

Recent studies have suggested altered visual processing for objects that are near the hands. We present three experiments that test whether an observer's hands near the display facilitate change detection. While performing the task, observers placed both hands either near or away from the display. When their hands were near the display, change dete...

Space constancy, the appearance of a stable visual world despite shifts of all visual input with each eye movement, has been explained historically with a compensatory signal (efference copy or corollary discharge) that subtracts the eye movement signal from the retinal image shift accompanying each eye movement. Quantitative measures have shown th...

Implicit change detection demonstrates how the visual system can benefit from stored information that is not immediately available to conscious awareness. We investigated the role of motor action in this context. In the first two experiments, using a one-shot implicit change-detection paradigm, participants responded to unperceived changes either w...

In grapheme-color synesthesia, observers perceive colors that are associated with letters and numbers. We tested the dynamic properties of this phenomenon by exposing two synesthetes to characters that rotate smoothly, that morph into other characters, that disappear abruptly, or that have colors either consistent or inconsistent with the correspon...

Recent studies have suggested an altered visual processing for objects that are near the hands; visual search rates were slower when an observer's hands were near the display, which was interpreted as a result of a detailed evaluation of objects. Slower reaction times, however, can also arise from a number of inhibitory processes and therefore do n...

Change blindness has been used to demonstrate the impoverished nature of visual representations. The verbal report measure in this paradigm underestimates information stored but not immediately available to consciousness because observers must be absolutely aware of changes and put them into words. Detection without awareness perhaps better assesse...

Both distributed coding, with its implication of neural reuse, and more specialized function have been recognized since the beginning of brain science. A controversy over imageless thought threw introspection into disrepute as a scientific method, making more objective methods dominate. It is known in information science that one element, such as a...

Chronometric studies provide strong support that mental imagery recruits perceptual processes (Shepard & Metzler, 1970; Shepard & Cooper, 1971). Further, there is recent evidence that information on effort is important in perceptual coding (Proffitt, 2003). If imagery recruits perceptual processes and perception is influenced by anticipated effort,...

How is our visual representation of natural scenes constructed with constantly-moving eyes? We introduce a new change blindness paradigm, combining Blackmore et al's moving-image paradigm (1995) and Sampanes, Tseng, and Bridgeman's progressive transformation paradigm (in press). A picture jumps repeatedly to random locations on a screen, with a sim...

In grapheme-color synesthesia, observers perceive colors that are associated with letters and numbers. We tested the dynamic limits of this phenomenon by exposing two synesthetes to characters that rotate smoothly, that morph into other characters, that disappear abruptly, or that have colors either consistent or inconsistent with the corresponding...

Summary Information about eye position comes from efference copy, a record of the innervation to the extraocular muscles that move the eye and proprioceptive signals from sensors in the extraocular muscles. Together they define extraretinal signals and indicate the position of the eye. By pressing on the eyelid of a viewing eye, the extraocular mus...

In metacontrast, a target is rendered invisible by a surrounding mask that appears after the target's offset, providing a tool for investigating temporal aspects of visual coding. Previous manipulations of target and mask duration have used constant stimulus intensity, so that longer-lasting stimuli appear brighter. When brightness is controlled by...

Mathematical analysis of Bible passages promises surprising new insights into the meanings of the texts. Relations among God, man and sheep, for example, are clarified with simple algebraic manipulation.

It has been demonstrated that visual objects that are present after saccadic eye movements act as landmarks for the localization of stimuli across saccades, facilitating space constancy (Deubel, 2004). We here study the temporal conditions under which landmark effects occur after saccadic eye movements, and during fixation. Two small objects were p...

Performing Kegel exercises following prostatectomy is helpful in restoring continence, but requires concentration to accomplish the required contractions consistently. Confusion and effort with executing the procedure can reduce compliance. A new method subdivides the exercises into segments that can be executed without counting. The patient perfor...

Chronometric studies provide strong support that mental imagery recruits perceptual processes [Shepard and Cooper, 1982 Mental Images and Their Transformations (Cambridge, MA: MIT Press)]. Recent studies suggest that anticipated effort influences perception (Proffitt et al, 2003 Psychological Science 14 106-112). If anticipated effort influences pe...

Studies of change blindness suggest that we bring only a few attended features of a scene, plus a gist, from one visual fixation to the next. We examine the role of gist by substituting an original image with a second image in which a substitution of one object changes the gist, compared with a third image in which a substitution of that object doe...

Everyone has the feeling that perception is usually accurate - we apprehend the layout of the world without significant error, and therefore we can interact with it effectively. Several lines of experimentation, however, show that perceived layout is seldom accurate enough to account for the success of visually guided behaviour. A visual world that...

Seemingly small changes in brain organization can have revolutionary consequences for function. An example is evolution's application of the primate action-planning mechanism to the management of communicative sequences. When feedback from utterances reaches the brain again through a mechanism that evolved to monitor action sequences, it makes anot...

Two theories define the relationship between sensory experience and perception of location. The doctrine of specific nerve energies relies on hard-wired, genetically specified relationships between stimulation and perception, modifiable only within limits by adaptation. In a newer sensorimotor account, experience tunes the relationship between stim...

Long-term rotational vestibulo-ocular (VOR) adaptation occurs during systematic dysmetria between visual and vestibular afferents, adjusting eye-rotation angular velocity to re-establish retinal stability of the visual field. Due to translational motion of the eyes during head rotation, VOR gain is higher when fixating near objects. The current stu...

Environment can provide information used in development – information that can appear to be genetically given and that was previously assumed to be so. Examples include growth of the eye until it achieves good focus, and structuring of receptive fields in the visual cortex by environmental information. The process can be called one-generation Lamar...

Efference copy, an internal brain signal informing the visual system of commands to move the eye, was the dominant explanation for visual space constancy for over a century. The explanation is not viable, however; the signal is to small, to slow, and too unreliable to support the perception of perfect constancy. Newer theories recognize that detail...

Extensive signal processing occurs in sensory systems before perception of object positions. Normally this processing is cognitively opaque, inaccessible to experience or behavioral experiment. Several experimental techniques, however, allow analysis of relationships between unconscious processing and subsequent conscious perception and action. In...

A distributed-coding model incorporating lateral inhibition in a simulated nerve network has been successful in accounting for many properties of backward masking (Bridgeman, 1971, 1978), linking modeling with neurophysiology and psychophysics. Metacontrast is a variety of backward masking that is of particular interest in uncovering properties of...

Lateral inhibition, the inhibition of neurons by other neurons at the same level, exists at several levels of the visual system. Implications of lateral inhibition for sensory coding and perception have been investigated with a mathematical model that accounts for many properties of metacontrast masking and brief storage of sensory information. Her...

Mathematical models are potentially as useful for culture as for evolution, but cultural models must have different designs from genetic models. Social sciences must borrow from biology the idea of modeling, rather than the structure of models, because copying the product is fundamentally different from copying the design. Transfer of most cultural...

In three experiments we studied change detection and identification when no extraneous transients were present in the image at the time of change. Each image consisted of 12 different objects, sorted by color into three different levels of probability of change. In Experiment 1, change of one object was detected and identified frequently in objects...

Hyperbolic theories have the fatal flaw that because of their vertical asymptote they predict irresistible choice of immediate rewards, regardless of future contingencies. They work only for simple situations. Theories incorporating intermediate unconscious choices are more flexible, but are neither exponential nor hyperbolic in their predictions....

Change blindness experiments suggest that rather than integrating the information in one visual fixation with the next fixation, only a few attended objects and a general gist are carried over from one fixation to the next. This result leads to a startling prediction: if perception of attended objects can be suppressed, it should be possible to exc...

It is known that dense objects seem heavier than larger, less dense objects of the same weight. We have investigated a related illusion, in which visual context biases the apparent weight of a single object. The apparatus is a cabin on a steep hillside near Santa Cruz, CA, tilted 17 degrees from vertical. From its ceiling hangs a weight on a chain....

Mirror systems must be supplemented by a planning capability to allow language to evolve. A capability for creating, storing, and executing plans for sequences of actions, having evolved in primates, was applied to sequences of communicatory acts. Language could exploit this already-existing capability. Further steps in language evolution may paral...

Although the sensorimotor account is a significant step forward, it cannot explain experiences of entoptic phenomena that violate normal sensorimotor contingencies but nonetheless are perceived as visual. Nervous system structure limits how they can be interpreted. Neurophysiology, combined with a sensorimotor theory, can account for space constanc...

A brief target that is visible when displayed alone can be rendered invisible by a trailing stimulus (metacontrast masking). It has been difficult to determine the temporal dynamics of masking to date because increments in stimulus duration have been invariably confounded with apparent brightness (Bloch's law). In the research reported here, stimul...

Displacements of visual stimuli during saccadic eye movements are often not noticed. We have demonstrated that saccadic suppression of image displacement can be eliminated by blanking the stimulus for a short period during and after the saccade (Deubel, Schneider, & Bridgeman, 1996). Here we report an experiment in which target visibility was inter...

Extending previous evidence for attentional shifts across auditory and visual modalities without the confound of the two modalities originating at different locations (Turatto et al. 2002), we investigated attention shifts between auditory and tactile modalities, and between tactile and visual modalities. Two stimuli (S1 and S2), either in the same...

VisPad is a new haptics design for visualizing data, constructed from commodity massage chair pads with custom controllers and interfaces to a computer. It is an output device for information transmitted to a user who sits on the pad. The user interface is unique in that it has a large feedback area and is passive in nature, where unlike most curre...

Cognitive judgments about an object's location are distorted by the presence of a large frame offset left or right of an observer's midline. Sensorimotor responses, however, seem immune to this induced Roelofs illusion, with observers able to accurately point to the target's location. These findings have traditionally been used as evidence for a di...

A new haptics design for visualizing data is constructed out of commodity massage pads and custom controllers and interfaces to a computer. It is an output device for information that can be transmitted to a user who sits on the pad. Two unique properties of the design are: (a) its large feedback area and (b) its passive nature, where unlike most c...

The perception/planning–control conception has a direct predecessor in a cognitive/sensorimotor scheme, where the cognitive branch includes Glover's perception and planning functions. The sensorimotor branch corresponds to Glover's control function. The cognitive/sensorimotor scheme, like the perception/planning–control scheme, differentiates betwe...

While the PREDICATE(x) structure requires close coordination of subject and predicate, both represented in consciousness, the cognitive (ventral), and sensorimotor (dorsal) pathways operate in parallel. Sensorimotor information is unconscious and can contradict cognitive spatial information. A more likely origin of linguistic grammar lies in the ma...

Though we share an irresistible introspection that we possess a will governing our behavior and not controlled by outside forces or previous states, empirical research shows that such a will does not exist. Rather, actions are triggered unconsciously, and a memory-related part of the brain produces a narrative to explain the behavior after the fact...

Change blindness is a failure to detect a change in an scene when the change occurs along with some visual disturbances. Disturbances are thought to play a delocalizing role that affects the saliency of the “target” transient signal coming from the change location, which would otherwise capture attention and render the change visible. For instance,...

Lack of symmetry of stone tools does not require that hominids making asymmetric tools are incapable of doing better. By analogy, differences between stone tools of early humans and modern technology arose without genetic change. A conservative assumption is that symmetry of stone artifacts may have arisen simply because symmetrical tools work bett...

Perception of image displacement is suppressed during saccadic eye movements. We probed the source of saccadic suppression of displacement by testing whether it selectively affects chromatic- or luminance-based motion information. Human subjects viewed a stimulus in which chromatic and luminance cues provided conflicting information about displacem...

Why and how people perceive the visual world as continuous and stable, despite the gross changes of its retinal projection that occur with each saccade, is one of the classic problems in perception. In the present paper, we argue that an important factor of visual stability and transsaccadic perception is formed by the reafferent visual information...

The Grand Illusion, the experience of a rich phenomenal visual world supported by a poor internal representation of that world, is echoed by petit illusions of the same sort. We can be aware of several aspects of an object or pattern, even when they are inconsistent with one another, because different neurological mechanisms code the various aspect...

Metacontrast, an apparent reduction in brightness of a target that is followed by a non-overlapping mask, has been modeled with simulated neural nets incorporating either recurrent lateral inhibition or forward and backward inhibition with lateral components. A one-layer lateral inhibitory model (B. Bridgeman, 1971, Psychological Review 78, 528-539...

We differentiate a cognitive branch of the visual system form a sensorimotor branch with the Roelofs effect, a perception that a target's position is biased in the direction opposite the offset of a surrounding fame. When a small fixed target is presented inside a frame that is offset to one side, normal humans perceive the target to be deviated in...

Neuroanatomy and neurophysiology are insufficient to specify function. Modeling is essential to elucidate function, but psychophysics is also required. An example is the cognitive and sensorimotor branches of the visual system: anatomy shows direct cross talk between the branches. Psychophysics in normal humans shows links from cognitive to sensori...

The brain holds two representations of visual space: a cognitive representation that drives perception, and a sensorimotor representation that controls visually guided behavior. We separate spatial values in the two with the Roelofs effect: a target within an off-center frame appears biased in a direction opposite the offset of the frame. The effec...

We distinguish two representations of visual space: a cognitive representation drives perception, and a sensorimotor representation controls visually guided behavior. Spatial values in the two representations are separated with the Roelofs effect: a target within an off-center frame appears biased in a location opposite the direction of the frame....

The current influence of the “behavior-based” approach to robotics (Brooks 1991), as well as the notion of “prerational intelligence” introduced in the present volume, challenge psychologists in one of their traditional fields of inquiry.

The visual field — the experienced visual space with objects on positions — is, in one way or another, the ‘product’ of calculations in retina and brain. It is often assumed, however, that for position perception no real calculations are required. The alternative is that the topographic location of an object in the outer world is represented geomet...

There are two independent representations of visual space in humans and primates. One, the cognitive or “what” system, processes image information that we use in pattern recognition and normal visual experience. The other, a sensorimotor or “how” system, controls visually guided behavior. Its memory is very brief, only long enough to execute an act...

The first controversy concerns the “efference copy,” the long-hypothesized internal signal that informs the rest of the brain about commands sent to the muscles. Its original conception, ironically, had a more cognitive context than its current instantiation in mathematical models. The brain could compare the effort of will with the sensory results...

The visual system captures a unique contrast between implicit and explicit representation where the same event (location of a visible object) is coded in both ways in parallel. A method of differentiating the two representations is described using an illusion that affects only the explicit representation. Consistent with predictions, implicit...

We differentiate a cognitive branch of the visual system from a sensorimotor branch with the Roelofs, effect, a perception that a target's position is biased in the direction opposite the offset of a surrounding frame. Previous research left the possibility that accurate motor responses to a perceptually mislocated target might be mediated by oculo...

The visual field — the experienced visual space with objects on positions — is, in one way or another, the ‘product’ of calculations in retina and brain. It is often assumed, however, that for position perception no real calculations are required. The alternative is that the topographic location of an object in the outer world is represented geomet...

Space constancy (the perception that the world remains stable despite eye movements) might be mediated by receptive fields with constant locations in the world rather than constant locations on the retina. In a strong form the hypothesis, receptive fields of single neurons would compensate for all eye movements, whereas in a weak form they would co...

Milner and Goodale review a wealth of evidence, much of it from their own research, showing that visually guided behavior and perception are controlled by two separate and quasi-independent 'visual brains'. Early evidence showed that motor ability was sometimes preserved despite simultaneous perceptual illusions, and work with patients has differen...

In two experiments, we examined the possibility that the human vestibulo-ocular reflex (VOR) is subject to dual adaptation (the ability to adapt to a sensory rearrangement more rapidly and/or more completely after repeated experience with it) and adaptive generalization (the ability to adapt more readily to a novel sensory rearrangement as a result...