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PubMed2001

From computing with numbers to computing with words. From manipulation of measurements to manipulation of perceptions.

Interest in issues relating to consciousness has grown markedly during the last several years. And yet, nobody can claim that consciousness is a well-understood concept that lends itself to precise analysis. It may be argued that, as a concept, consciousness is much too complex to fit into the conceptual structure of existing theories based on Aristotelian logic and probability theory. An approach suggested in this paper links consciousness to perceptions and perceptions to their descriptors in a natural language. In this way, those aspects of consciousness which relate to reasoning and concept formation are linked to what is referred to as the methodology of computing with words (CW). Computing, in its usual sense, is centered on manipulation of numbers and symbols. In contrast, computing with words, or CW for short, is a methodology in which the objects of computation are words and propositions drawn from a natural language (e.g., small, large, far, heavy, not very likely, the price of gas is low and declining, Berkeley is near San Francisco, it is very unlikely that there will be a significant increase in the price of oil in the near future, etc.). Computing with words is inspired by the remarkable human capability to perform a wide variety of physical and mental tasks without any measurements and any computations. Familiar examples of such tasks are parking a car, driving in heavy traffic, playing golf, riding a bicycle, understanding speech, and summarizing a story. Underlying this remarkable capability is the brain's crucial ability to manipulate perceptions--perceptions of distance, size, weight, color, speed, time, direction, force, number, truth, likelihood, and other characteristics of physical and mental objects. Manipulation of perceptions plays a key role in human recognition, decision and execution processes. As a methodology, computing with words provides a foundation for a computational theory of perceptions: a theory which may have an important bearing on how humans make--and machines might make--perception-based rational decisions in an environment of imprecision, uncertainty, and partial truth. A basic difference between perceptions and measurements is that, in general, measurements are crisp, whereas perceptions are fuzzy. One of the fundamental aims of science has been and continues to be that of progressing from perceptions to measurements. Pursuit of this aim has led to brilliant successes. We have sent men to the moon; we can build computers that are capable of performing billions of computations per second; we have constructed telescopes that can explore the far reaches of the universe; and we can date the age of rocks that are millions of years old. But alongside the brilliant successes stand conspicuous underachievements and outright failures. We cannot build robots that can move with the agility of animals or humans; we cannot automate driving in heavy traffic; we cannot translate from one language to another at the level of a human interpreter; we cannot create programs that can summarize non-trivial stories; our ability to model the behavior of economic systems leaves much to be desired; and we cannot build machines that can compete with children in the performance of a wide variety of physical and cognitive tasks. It may be argued that underlying the underachievements and failures is the unavailability of a methodology for reasoning and computing with perceptions rather than measurements. An outline of such a methodology--referred to as a computational theory of perceptions--is presented in this paper. The computational theory of perceptions (CTP) is based on the methodology of CW. In CTP, words play the role of labels of perceptions, and, more generally, perceptions are expressed as propositions in a natural language. CW-based techniques are employed to translate propositions expressed in a natural language into what is called the Generalized Constraint Language (GCL). In this language, the meaning of a proposition is expressed as a generalized constraint, X isr R, where X is the constrained variable, R is the constraining relation, and isr is a variable copula in which r is an indexing variable whose value defines the way in which R constrains X. Among the basic types of constraints are possibilistic, veristic, probabilistic, random set, Pawlak set, fuzzy graph, and usuality. The wide variety of constraints in GCL makes GCL a much more expressive language than the language of predicate logic. In CW, the initial and terminal data sets, IDS and TDS, are assumed to consist of propositions expressed in a natural language. These propositions are translated, respectively, into antecedent and consequent constraints. Consequent constraints are derived from antecedent constraints through the use of rules of constraint propagation. The principal constraint propagation rule is the generalized extension principle. (ABSTRACT TRUNCATED)

Consciousness↗
PubMed2006

Stigma in response to mental disorders: a comparison of Australia and Japan.

BACKGROUND: There are few national or cross-cultural studies of the stigma associated with mental disorders. Australia and Japan have different systems of psychiatric health care, and distinct differences in cultural values, but enjoy similar standards of living. This study seeks to compare the nature and extent of stigma among the public in the two countries. METHODS: A household survey of the public was conducted in each country using similar methodologies. The Australian study comprised a national survey of 3998 adults aged over 18 years. The Japanese survey involved 2000 adults aged 20 to 69 from 25 regional sites distributed across the country. Interviewees reported their personal attitudes (personal stigma, social distance) and perceptions of the attitudes of others (perceived stigma, perceived discrimination) in the community with respect to four case vignettes. These vignettes described a person with: depression; depression with suicidal ideation; early schizophrenia; and chronic schizophrenia. RESULTS: Personal stigma and social distance were typically greater among the Japanese than the Australian public whereas the reverse was true with respect to the perception of the attitudes and discriminatory behaviour of others. In both countries, personal stigma was significantly greater than perceived stigma. The public in both countries showed evidence of greater social distance, greater personal stigma and greater perceived stigma for schizophrenia (particularly in its chronic form) than for depression. There was little evidence of a difference in stigma for depression with and without suicide for either country. However, social distance was greater for chronic compared to early schizophrenia for the Australian public. CONCLUSION: Stigmatising attitudes were common in both countries, but negative attitudes were greater among the Japanese than the Australian public. The results suggest that there is a need to implement national public awareness interventions tailored to the needs of each country. The current results provide a baseline for future tracking of national stigma levels in each country.

Adult↗
PubMed2001

Configuration specificity in bisection acuity.

Crucial for the perception of form are the spatial relationships between the elements of a visual stimulus. To investigate the mechanisms involved in coding the distance between visual stimuli, thresholds for detecting whether a central marker accurately bisects a spatial interval were compared for a variety of configurations. Thresholds are best when all three members of the bisection configuration are identical. Performance is impaired, often by as much as a factor of two, when the outer delimiters of the spatial interval differ from the central marker in either length, orientation or contrast polarity. Illusory contours act poorly as borders for bisection by a central line. Disparity thresholds are not affected by orientation differences between test and flanking lines. Because in peripheral vision bisection acuity improves with practice, transfer of training between configurations can be used to gauge overlap of neural processing mechanisms. Transfer is complete only between patterns where all markers are similar, reduced when the outer markers differ by 20 degrees in orientation and absent when they are orthogonal. The dependence of bisection discrimination on similarity between the elements of the stimulus demonstrates that the encoding of spatial location and spatial extent are coupled to the coding of other stimulus properties.

Contrast Sensitivity↗
PubMed1994

Subjective landmarks in perception and memory for spatial location.

Four experiments investigated the use of cognitive strategies for encoding spatial location in visual figures. Subjects reproduced the position of a dot in a square figure that had distance markers placed along two sides. Subjects' responses were biased toward imaginary points of intersection formed by the distance markers when subjects responded from memory (Experiment 1) or while viewing the figures (Experiment 2). Dots located at an intersection point were reproduced more accurately than those located off an intersection. These findings demonstrate that empty regions of a figure can serve as subjective landmarks for spatial localization. In Experiment 3, dot relocation was found to be similarly distorted toward physical cross marks placed at the intersections of distance markers, supporting the landmark hypothesis. The attraction of dots to intersection points depends on the viewer employing a strategy of mentally projecting from distance markers to form imaginary intersections, which makes intersection points salient landmarks for coding location of nearby stimulus dots. In Experiment 4, attraction toward intersection points was observed only when subjects employed the projection strategy and not when instructed to use a different encoding strategy.

Adult↗
PubMed2005

The scaling of information to action in visually guided braking.

Braking to avoid a collision can be controlled by keeping the deceleration required to stop (i.e., ideal deceleration) in the "safe" region below maximum deceleration, but maximum deceleration is not optically specified and can vary as conditions change. When brake strength was manipulated between participants using a simulated braking task, the ratio of ideal to maximum deceleration at brake onset was invariant across groups, suggesting that calibration involves scaling information about ideal deceleration in intrinsic units of maximum deceleration. Evidence of rapid recalibration was found when brake strength was manipulated within participants, and the presence of external forces that affect brake dynamics resulted in biases in performance. Discussion focuses on the role of calibration, internal models, and affordance perception in visually guided action.

Acceleration↗
PubMed2003

Accuracy and precision of binocular 3-D motion perception.

In principle, information for 3-D motion perception is provided by the differences in position and motion between left- and right-eye images of the world. It is known that observers can precisely judge between different 3-D motion trajectories, but the accuracy of binocular 3-D motion perception has not been studied. The authors measured the accuracy of 3-D motion perception. In 4 different tasks, observers were inaccurate, overestimating trajectory angle, despite consistently choosing similar angles (high precision). Errors did not vary consistently with target distance, as would be expected had inaccuracy been due to misestimates of viewing distance. Observers appeared to rely strongly on the lateral position of the target, almost to the exclusion of the use of depth information. For the present tasks, these data suggest that neither an accurate estimate of 3-D motion direction nor one of passing distance can be obtained using only binocular cues to motion in depth. ((c) 2003 APA, all rights reserved)

Discrimination, Psychological↗
PubMed1991

Representation of spatial structure in reaching to a visual target.

Reaches made without feedback to positions on an object's surface reflect the spatial form of the surface. In Experiment 1, the reaching pattern varied with the stimulus surface's spatial attributes, consistent with a point-by-point perceptual representation of the surface. In Experiment 2, systematic reaching errors were determined solely by target position regardless of surface structure, implying a highly consistent representation of location. In Experiment 3, illusory slant was imparted to a surface by an aniseikonic lens. Individual variations in directly judged slant were reflected in the reaching pattern, implying organization of local perceptual representation of location and global perception of spatial attributes of the stimulus into a coherent structure.

Adult↗
PubMed1996

The Doppler illusion: the influence of dynamic intensity change on perceived pitch.

Four studies illustrate a new auditory illusion associated with the Doppler effect and demonstrate a new influence of dynamic intensity change on perceived pitch. Experiment 1 confirmed the existence of a popular belief that the pitch of a moving sound source rises as the source approaches. Because there is no corresponding rise in frequency, the authors refer to the perceived pitch rise as the Doppler illusion. Experiment 2 confirmed that the effect occurs perceptually, so the belief in a "naive principle" of physics has a perceptual basis. Experiment 3 confirmed the effect does not occur under matched static conditions. Experiment 4 showed that the influence of dynamic intensity change on perceived pitch occurs outside the realm of Doppler stimuli. The findings support a dynamic dimensional interaction of pitch and loudness, with marked differences in the perception of pitch and loudness under static and dynamic conditions.

Adult↗
PubMed2006

Perceptual distance and the constancy of size and stereoscopic depth.

The relationship between distance and size perception is unclear because of conflicting results of tests investigating the size-distance invariance hypothesis (SDIH), according to which perceived size is proportional to perceived distance. We propose that response bias with regard to measures of perceived distance is at the root of the conflict. Rather than employ the usual method of magnitude estimation, the bias-free two-alternative forced choice (2AFC) method was used to determine the precision (1/sigma) of discriminating depth at different distances. The results led us to define perceptual distance as a bias free power function of physical distance, with an exponent of approximately 0.5. Similar measures involving size differences among stimuli of equal angular size yield the same power function of distance. In addition, size discrimination is noisier than depth discrimination, suggesting that distance information is processed prior to angular size. Size constancy implies that the perceived size is proportional to perceptual distance. Moreover, given a constant relative disparity, depth constancy implies that perceived depth is proportional to the square of perceptual distance. However, the function relating the uncertainties of depth and of size discrimination to distance is the same. Hence, depth and size constancy may be accounted for by the same underlying law.

Adult↗
PubMed2000

Haptic interaction with virtual objects. Spatial perception and motor control.

This paper considers interaction of the human arm with "virtual" objects simulated mechanically by a planar robot. Haptic perception of spatial properties of objects is distorted. It is reasonable to expect that it may be distorted in a geometrically consistent way. Three experiments were performed to quantify perceptual distortion of length, angle and orientation. We found that spatial perception is geometrically inconsistent across these perceptual tasks. Given that spatial perception is distorted, it is plausible that motor behavior may be distorted in a way consistent with perceptual distortion. In a fourth experiment, subjects were asked to draw circles. The results were geometrically inconsistent with those of the length perception experiment. Interestingly, although the results were inconsistent (statistically different), this difference was not strong (the relative distortion between the observed distributions was small). Some computational implications of this research for haptic perception and motor planning are discussed.

Distance Perception↗
PubMed1990

Size constancy at birth: newborn infants' responses to retinal and real size.

Two experiments are described whose aim was to investigate whether perception of size at birth is determined solely by proximal (retinal) stimulation, or whether newborn babies have the ability to perceive an object's real size across changes in distance. In Experiment 1, preferential looking between pairs of stimuli which varied in real size and viewing distance was found to be solely determined by retinal size, suggesting that changes to proximal stimulation can have profound effects on newborns' looking behavior. However, in Experiment 2 newborns were desensitized to changes in distance (and retinal size) during familiarization trials, and subsequently strongly preferred a different sized object to the familiar one, suggesting that the real size had been perceived as constant across the familiarization trials. These results confirm Granrud's (1987) findings that size constancy is present at birth.

Attention↗
PubMed2006

The processing of linear perspective and binocular information for action and perception.

To investigate the processing of linear perspective and binocular information for action and for the perceptual judgment of depth, we presented viewers with an actual Ames trapezoidal window. The display, when presented perpendicular to the line of sight, provided perspective information for a rectangular window slanted in depth, while binocular information specified a planar surface in the fronto-parallel plane. We compared pointing towards the display-edges with perceptual judgment of their positions in depth as the display orientation was varied under monocular and binocular view. On monocular trials, pointing and depth judgment were based on the perspective information and failed to respond accurately to changes in display orientation because pictorial information did not vary sufficiently to specify the small differences in orientation. For binocular trials, pointing was based on binocular information and precisely matched the changes in display orientation whereas depth judgment was short of such adjustment and based upon both binocular and perspective-specified slant information. The finding, that on binocular trials pointing was considerably less responsive to the illusion than perceptual judgment, supports an account of two separate processing streams in the human visual system, a ventral pathway involved in object recognition and a dorsal pathway that produces visual information for the control of actions. Previously, similar differences between perception and action were explained by an alternate explanation, that is, viewers selectively attend to different parts of a display in the two tasks. The finding that under monocular view participants responded to perspective information in both the action and the perception task rules out the attention-based argument.

Adult↗