bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of flexible fibreoptic bronchoscopy in evaluation of pulmonary diseases in children with congenital cardiac disease
Authors: Efrati Ori , Gonik Udi , Modan-Moses Dalit , Bielorai Bella , Barak Asher , Vardi Amir , Paret Gideon , Mishaly David , Toren Amos
Published: January 2007

Background:Diseases of the lungs and airways can be life-threatening in patients with congenital cardiac disease. External compression, and tracheobronchomalacia, as well as pathology of the large airways, can cause respiratory symptoms such as wheezing, stridor, fever, and dyspnoea, along with producing difficulty to wean the patient from mechanical ventilation. A definite diagnosis may be achieved by fibreoptic flexible bronchoscopy.Aims:To characterize the patients who underwent bronchoscopy for respiratory diseases associated with congenital cardiac disease, and to evaluate the safety, total diagnostic rate, and diagnostic rate, which yielded alteration of treatment in this group of patients.Methods:We reviewed retrospectively the records of 39 patients with congenital cardiac disease associated with abnormalities of the airways who underwent 49 fibreoptic bronchoscopies between 1999 and 2004. The patients were evaluated with regard to rate of diagnosis, the rate of procedures that resulted in alteration of management, and the rate of complications.Results:Fibreoptic flexible bronchoscopy was safe, and contributed to a specific diagnosis in almost nine-tenths of the procedures. A specific diagnosis that resulted in treatment alteration was achieved in one-fifth of the procedures.Conclusions:Fibreoptic flexible bronchoscopy has an important role in the evaluation of pulmonary abnormalities in patients with congenital cardiac diseases, and should be considered as an initial diagnostic tool that may guide the clinician with regard to the proper therapy.
Paediatric Cardiology – James William Brown
Authors: Wilkinson James L. , Gerlis Leon M. , Anderson Robert H.
Published: January 2007

“When the history of congenital heart disease comes to be written, Brown will be given a high and honourable place along with Farre, Peacock, Fallot, Théremin, Vierordt, and Maude Abbott, as one whose labours have contributed vitally to the subject.”1
Biogeochemical simulation of nitrous oxide cycle based on the major nitrogen processes
Authors: Sorai Masao , Yoshida Naohiro , Ishikawa Masamichi
Published: January 2007

We modeled the biogeochemical nitrogen cycle with specific emphasis on N2O behavior to describe the global N2O cycle system quantitatively. Here all the major nitrogen cycle processes are included plus the processes directly related to N2O. The model includes 24 nitrogen reservoirs: 3 in the stratosphere (N2O, N2, and NOx), 4 in the troposphere (N2O, N2, NH3, and NOx), 7 on land (biospheric, N2O, NOx, PON, DON, NH4+, and NO3−), 6 in surface‐ocean (biospheric, PON, DON, N2O, NH4+, and NO3−), 3 in the deep ocean (N2O, NH4+, NO3−), and sedimentary organic nitrogen. The exploration of the steady state flux combination, which produces the tropospheric N2O concentration profile consistent with observations, provided the most likely estimates of the N2O emissions from soils, rivers, and oceans, including contributions from nitrification and denitrification. Full incorporation of nitrogen species facilitated an analysis of the influences of various nitrogen cycle processes on tropospheric N2O concentration. Our sensitivity analyses revealed that the tropospheric N2O concentration was linked closely to other nitrogen species and was especially sensitive to terrestrial biological activities via nitrogen fixation, nitrogen assimilation, and ammonification. This result implies that the N2O budget in the troposphere can be constrained well by these terrestrial processes.
On the inherent asymmetric nature of the complementary relationship of evaporation
Authors: Szilagyi Jozsef
Published: January 2007

New theoretical considerations indicate that the complementary relationship (CR) of evaporation is inherently asymmetric when the time rate of change between actual and apparent potential evaporations is considered. The theory also estimates the extent of this asymmetry as a function of the surface temperature and predicts that a symmetric CR, independent of the surface temperature, can only be expected when no energy exchange between the source of the apparent potential evaporation process and its surroundings occurs, a rather unrealistic situation. The derived asymmetric CR is employed for operational evaporation estimations. The parameters of the proposed practical evaporation estimation model are from the Priestley‐Taylor and Penman equations.
Sildenafil reduces L‐NAME‐induced severe hypertension and worsening of myocardial ischaemia–reperfusion damage in the rat
Authors: Rossoni G , Manfredi B , De Gennaro Colonna V , Berti M , Guazzi M , Berti F
Published: January 2007

Background and purpose:

Phosphodiesterase‐5 inhibitors are beneficial in pulmonary hypertension and congestive heart failure, the two conditions associated with coronary heart disease and ischaemia. We investigated whether sildenafil counteracts the cardiovascular alterations induced by N
ω‐nitro‐L‐arginine methyl ester (L‐NAME) in the rat.

Experimental approach:

Sildenafil was given orally to rats at doses of 0.37, 0.75 or 1.5 mg kg−1day−1 for four weeks, either alone or with L‐NAME (35‐40 mg kg−1 day−1 in the drinking water). Systolic blood pressure and urinary parameters (6‐keto‐prostaglandin F1α, thromboxane B2, 8‐isoprostane‐prostaglandin F2α and nitrite/nitrate) were measured in conscious rats. Isolated hearts were subjected to low flow ischaemia–reperfusion, and myocardial levels of guanosine 3′, 5′cyclic monophosphate (cGMP) were determined. Endothelial vascular dysfunction was examined in aortic rings.

Key results:

Sildenafil dose‐dependently prevented the rise in systolic blood pressure in L‐NAME‐treated rats. This activity was associated with a normalization of urinary 8‐isoprostane‐prostaglandin F2α and other biochemical parameters. In perfused hearts, the post‐ischaemic ventricular dysfunction was worse in preparations from L‐NAME‐treated rats than in controls. Sildenafil dose‐dependently reduced this effect, and creatine kinase and lactate dehydrogenase release were lower too. cGMP levels, which were low in myocardial tissue from L‐NAME‐treated rats, were restored by sildenafil. In noradrenaline‐precontracted aortic rings from L‐NAME‐treated rats acetylcholine lost its vasorelaxant effect, and sildenafil restored it.

Conclusion and implications:

In a rat model of chronic nitric oxide deprivation, where hypertension and aggravation of post‐ischaemic ventricular dysfunction are associated with loss of vascular endothelium‐relaxant function, sildenafil provided significant cardiovascular protection, primarily by maintaining tissue cGMP levels.

British Journal of Pharmacology (2007) 150, 567–576. doi:10.1038/sj.bjp.0707131
The Dependence of Monocular Rivalry on Orientation
Authors: Campbell F W , Gilinsky A S , Howell E R , Riggs L A , Atkinson J
Published: January 2007

If two gratings with a sinusoidal luminance profile are crossed and if each has a different colour then they are seen to alternate; first one dominates and then the other. Part of the time both are seen. The rate of this monocular rivalry varies with the angle between the two gratings. If the two are lined up in parallel the percept is quite stable and remains so until their orientation is about 15° to 20° apart. The rate of alternation then increases rapidly reaching a maximum rate of 30 per minute.

The orientational selectivity of the rivalry suggests that the orientational properties of the neurones in the visual cortex discovered by Hubel and Wiesel are involved. Acknowledgements. We wish to thank Professor Peter M. Milner for his keen interest in these experiments and for acting as a subject. F.W.C. is supported by a grant from the Medical Research Council. The work of A.S.G. during her visit to Cambridge was supported in part by a research grant GB-31029 from the National Science Foundation. E.R.H. was awarded a Wellcome Trust Fellowship while in Cambridge.
The Process of ‘Taking-into-Account’ in Visual Perception
Authors: Epstein W
Published: January 2007

In order to secure useful information the perceptual system must combine information present in the retinal counterpart of the to-be-discriminated distal variable with information about other variables that affect the state of the retinal counterpart. This combinatorial process may be called—following Woodworth's lead—the process of ‘taking-into-account’.

Seven applications of the ‘taking-into-account’ hypothesis are described. Salient features of the hypothesis are examined and the empirical status of the hypothesis is summarized and evaluated. Finally a model of the information-processing sequence suggested by the hypothesis is presented.
Orientation-Specific Learning in Stereopsis
Authors: Ramachandran V S , Braddick O
Published: January 2007

Inexperienced observers show a delay before experiencing the stereoscopic percept from a random-dot stereo pair. This perception time is progressively reduced with repeated exposures of the stereogram. We have investigated the specificity of this perceptual learning effect, using stereograms made up of short oblique line elements. Learning with a stereogram consisting of 45° line elements transferred completely to an uncorrelated pattern with the same element orientation, but there was a marked failure of transfer to a pattern whose elements had the opposed oblique orientation. Thus the stereoscopic skill that has been acquired may be specific to those orientation analysers that were stimulated during the training period.
Some New Subjective Contours in Random-Line Stereograms
Authors: Julesz Bela , Frisby John P
Published: January 2007

Some new subjective contours are described and it is suggested that both these and previously observed disparity-based illusory contours can be explained simply in terms of the magnetic dipole model of stereopsis without any reference to gestalt or cognitive factors.
Eye Movements during the Viewing of Necker Cubes
Authors: Ellis Stephen R , Stark Lawrence
Published: January 2007

Eye movements were recorded while subjects viewed a Kopfermann-like series of Necker cubes and signaled perceptual reversals. At the instant of reversal, subjects tend to fixate the vicinity of the externally appearing corner. These fixations at the instant of reversal tend to have longer duration than those immediately before or after. The longer fixation times associated with perceptual reversal probably reflect the time required to construct the alternate three-dimensional interpretation of the cube. After construction of this new model, the subject then fixates the vicinity of the newly interpreted externally appearing corner.
Two Categorical Stages of Object Recognition
Authors: Warrington Elizabeth K , Taylor Angela M
Published: January 2007

Visual object recognition was investigated in a group of eighty-one patients with right- or left-hemisphere lesions. Two tasks were used, one maximizing perceptual categorization by physical identity, the other maximizing semantic categorization by functional identity. The right-hemisphere group showed impairment on the perceptual categorization task and the left-hemisphere group were impaired on the semantic categorization task. The findings are discussed in terms of categorical stages of object recognition. A tentative model of their cerebral organization is suggested.
Is Accommodation Colorblind? Focusing Chromatic Contours
Authors: Wolfe Jeremy M , Owens D Alfred
Published: January 2007

Two adjacent regions define an edge if they differ in either color or luminance. If the difference is purely chromatic, the edge is said to be isoluminant. Isoluminant contours are often perceptually unstable. Perhaps some of this instability could be explained if isoluminant contours were difficult to bring into focus. To test this hypothesis, a vernier optometer was used to measure the accuracy of steady-state accommodation for the vertical boundary of a red—green bipartite field. This edge was presented at optical distances of 0, 1·5, 3·0, and 4·5 diopters, with brightness contrasts between the two hemifields of 0% (isoluminant), 15%, 58%, and 100%. Accommodation was essentially unresponsive to the isoluminant edge and exhibited increasing focusing accuracy with increased brightness contrast. Control experiments replicated this finding for red—orange, green—blue, and white—white fields. These results imply that luminance contrast is a necessary stimulus for monocular accommodation. Inappropriate accommodation may be a factor contributing to the perceptual instability of isoluminant patterns.
Wundt's Views on Sensations of Innervation: A Reevaluation
Authors: Ross Helen E , Bischof Klaus
Published: January 2007

It is sometimes stated that Wundt believed in the primacy of ‘sensations of innervation’ in the control of eye and limb position, to the exclusion of afferent feedback. Wundt's own statements on the subject are traced through the six editions of the Grundzüge: he believed that sensations of innervation were a contributory factor along with peripheral feedback; but in the fourth edition he dropped the term and subsumed them under ‘central sensations of senses’, because increased neurophysiological knowledge made a literal interpretation of the original term impossible. In the fifth edition he developed a more precise model of central processes, described as ‘sensory costimulation’, and an additional idea of ‘reproduced’ or conditioned sensations. He mentions clinical evidence on the perception of eye and limb position and of weight by paralysed and other subjects. This evidence is discussed in relation to modern theories. It is concluded that Wundt's later theories have some similarities with modern ‘hybrid’ theories of efference-contingent afference.
Perceived Loudness and Visually-Determined Auditory Distance
Authors: Mershon Donald H , Desaulniers Douglas H , Kiefer Stephan A , Amerson Thomas L , Mills Jeanne T
Published: January 2007

Three experiments were conducted to determine whether variations in the perceived distance to a test sound could influence its loudness in the absence of physical changes in sound-level. The phenomenon of visual capture provided the means for manipulating apparent distance. A ‘dummy’ loudspeaker was used to vary the apparent source location of a short noise stimulus while the true source of this sound remained fixed (and hidden) with respect to the observer. Sound-levels from 40 to 75 dB(A) were presented to independent groups of observers in either anechoic or semi-reverberant acoustical environments. In general, reported loudness increased with perceived distance. This finding has implications for conceptualizing the phenomenon of loudness constancy.
Do Background Depth Gradients Facilitate Object Identification?
Authors: Biederman Irving
Published: January 2007

A number of experiments have demonstrated that an object in a coherent scene can be more accurately identified than when in a jumbled scene or a display of unrelated objects. An experiment was designed to test whether the identification of an object (from a set of six) would be faster and more accurate if the objects were presented against a background gradient that conferred a unifying depth effect on the six objects. No benefit of this background was found. In fact, the accuracy of the identification of objects against a depth background was found to be lower than that of objects which were presented against either no background or a control regular grid background. It is concluded that the perceptual advantage of objects appearing in a well-formed scene derives from semantic relations that are defined between such objects.
The Aesthetics of Colour
Authors: McManus I C , Jones Amanda L , Cottrell Jill
Published: January 2007

A paired comparison experiment is described in which preferences for Munsell colour patches were elicited from 54 subjects. Value, chroma, and hue preferences were examined separately. Individuals differed in their preferences for value and chroma, and also for hue. There were also sex differences in preference. Overall the majority of subjects showed a preference for blue hues and a dislike for yellow hues, thus demonstrating a continuity between animal and human colour aesthetics.
How Many Trees Does it Take to Make a Forest?
Authors: Navon David
Published: January 2007

In order to study the relative perceptual availability of global and local features in very sparse patterns, subjects were asked to make ‘same’/‘different’ judgments on pairs of geometrical figures and the times needed to detect global and local differences were compared. With triangular patterns a global precedence was found which could be attributed to size differences. With rectangular patterns global precedence was larger, not accounted for by size differences, and indifferent both to the number of elements and to their spacing. Thus it was demonstrated that global precedence may hold for patterns with as few as four elements. Patterns with smooth edges could be compared much more quickly than patterns with serrated eges. It is proposed that configurational properties of some of the patterns interfered with the encoding of their global structures or with comparing them. It is argued that the results support a principle of global addressability which postulates that visual schemata are mainly addressed through their global constituents.
Orientation Sensitivity in the Peripheral Visual Field
Authors: Spinelli Donatella , Bazzeo Aurora , Vicario Giovanni B
Published: January 2007

Orientation sensitivity in the peripheral visual field has been tested in two tasks: (a) setting horizontal the orientation of a grating at various retinal eccentricities, and (b) matching the orientation of a peripherally viewed grating as close as possible to an oblique reference viewed foveally. Both performances fall off with increasing retinal eccentricity. Magnification of the stimulus optimizes peripheral performance. Peripheral performance, optimized by magnification, varies with retinal eccentricity. It approaches, but does not reach, the foveal value (tested by the same method) at 10 deg of eccentricity, and is much lower at 20 and 30 deg of eccentricity.
PMF: A Stereo Correspondence Algorithm Using a Disparity Gradient Limit
Authors: Pollard Stephen B , Mayhew John E W , Frisby John P
Published: January 2007

The advantages of solving the stereo correspondence problem by imposing a limit on the magnitude of allowable disparity gradients are examined. It is shown how the imposition of such a limit can provide a suitable balance between the twin requirements of disambiguating power and the ability to deal with a wide range of surfaces. Next, the design of a very simple stereo algorithm called PMF is described. In conjunction with certain other constraints used in many other stereo algorithms, PMF employs a limit on allowable disparity gradients of 1, a value that coincides with that reported for human stereoscopic vision. The excellent performance of PMF is illustrated on a series of natural and artificial stereograms. Finally, the differences between the theoretical justification for the use of disparity gradients for solving the stereo correspondence problems presented in the paper and others that exist in the stereo algorithm literature are discussed.
A Test of the Minimum Principle Requires a Perceptual Coding System
Authors: Boselie Frans , Leeuwenberg Emanuel
Published: January 2007

The minimum principle states that a perceiver will see the simplest possible interpretation of a pattern. Some theorists of human perception take this principle as a core explanatory concept. Others, especially Rock and Hochberg, hold the view that a perceptual minimum principle is untenable. Rock presents a great number of demonstrations which, in his opinion, rule out the minimum principle. Hochberg states that ‘impossible’ figures especially present a difficulty for this principle. It is argued here that, in order to test the minimum principle, a method is needed to describe interpretations of patterns in such a way that they can be ordered according to simplicity. To achieve this, Leeuwenberg's coding system was used. The analyses reported here of the patterns which Rock produces as evidence against the principle show that, contrary to Rock's claim, the way these patterns are preferentially perceived provides strong support for the minimum principle. Next, it is demonstrated that interpreting certain patterns as ‘impossible’ figures is not incompatible with the principle. Finally, it is argued that a test of the minimum principle is necessarily conflated with two other hypotheses, one concerning the metric of simplicity and one concerning the task conception of the experimental subjects.
The Perception of Time in Scale Model Environments
Authors: Mitchell C Thomas , Davis Roy
Published: January 2007

It has been claimed that when subjects observe differently-scaled model environments their experience of temporal duration is compressed relative to standard clock time in the same proportion as the scale of the model being observed. A series of experiments is reported in which subjects made judgements of duration while observing model environments of different scale. In each experiment, two similar model environments of different scale were presented. Three different kinds of model were used: scale model railways, sitting-room models, and abstract nonrepresentional models. Despite considerable individual variability, significant effects were obtained. Smaller scale was, up to a point, related to a compression of subjective time relative to clock time, although the effect was nowhere near as great as that previously reported. Also, when scale was reduced beyond a certain point the effect on judgements of duration was eliminated, or even reversed. It is suggested that the effect of time compression is related to differences in the density of the information to be processed in environments of different scale, and that there may be an optimum value for information density related both to the scale and to the type of environment.
Serial and Parallel Search in Pattern Vision?
Authors: Steinman Scott B
Published: January 2007

The nature of the processing of combinations of stimulus dimensions in human vision has recently been investigated. A study is reported in which visual search for suprathreshold positional information—vernier offsets, stereoscopic disparity, lateral separation, and orientation—was examined. The initial results showed that reaction times for visual search for conjunctions of stereoscopic disparity and either vernier offsets or orientation were independent of the number of distracting stimuli displayed, suggesting that disparity was searched in parallel with vernier offsets or orientation. Conversely, reaction times for detection of conjunctions of vernier offsets and orientation, or lateral separation and each of the other positional judgements, were related linearly to the number of distractors, suggesting serial search. However, practice has a significant effect upon the results, indicative of a shift in the mode of search from serial to parallel for all conjunctions tested as well as for single features. This suggests a reinter-pretation of these and perhaps other studies that use the Treisman visual search paradigm, in terms of perceptual segregation of the visual field by disparity, motion, color, and pattern features such as colinearity, orientation, lateral separation, or size.
A Mechanism for the Direct Perception of Change: The Example of Bacterial Chemotaxis
Authors: Pittenger John B , Dent Cathy H
Published: January 2007

The relationship between the behavior of single-celled organisms and cognition in higher animals is explored. Recent research and theory in bacterial chemotaxis are presented, together with a discussion of the implications of chemotaxis for perceptual theory. A number of parallels between chemotaxis and perception in higher organisms are drawn. It is suggested that Koshland's model of the chemical processes controlling chemotaxis is an example of a mechanism for direct perception of change and can help elucidate Runeson's work on ‘smart mechanisms’ of perception. It is argued, more generally, that the growing body of knowledge about the perceptual activities of lower organisms should be used to broaden the factual base on which theories of perception are constructed: eg explication of perceptual parallels between humans and lower organisms should help clarify the nature of these phenomena in humans and, perhaps, help in the development of theories of greater generality. Also, the debate between direct and indirect theories of perception may be advanced by analysis of the specific mechanisms used by lower organisms. Contrasts to mediated perception are pointed out and arguments for the relative simplicity and explanatory power of theories of direct perception are provided.
An Astable Multivibrator Model of Binocular Rivalry
Authors: Lehky Sidney R
Published: January 2007

The behavior of a neural network model for binocular rivalry is explored through the development of an analogy between it and an electronic astable multivibrator circuit. The model incorporates reciprocal feedback inhibition between signals from the left and the right eyes prior to binocular convergence. The strength of inhibitory coupling determines whether the system undergoes rivalrous oscillations or remains in stable fusion: strong coupling leads to oscillations, weak coupling to fusion. This implies that correlation between spatial patterns presented to the two eyes can affect the strength of binocular inhibition. Finally, computer simulations are presented which show that a reciprocal inhibition model can reproduce the stochastic behavior of rivalry. The model described is a counterexample to claims that reciprocal inhibition models as a class cannot exhibit many of the experimentally observed properties of rivalry.
Development of Orientation Discrimination in Infancy
Authors: Atkinson Janette , Hood Bruce , Wattam-Bell John , Anker Shirley , Tricklebank Johanna
Published: January 2007

It has previously been found by us, with a visual evoked potential (VEP) measure, that orientation discrimination of dynamic patterns in infants can be demonstrated from around 6 weeks after birth. Experiments are reported in which orientation discrimination was measured behaviourally, in two infant control habituation procedures, with both dynamic and static patterns. When dynamic patterns identical to those in our previous VEP studies were used, the first positive evidence of orientation discrimination was found at around 6 weeks postnatally. The time course of both the VEP and the behavioural measures was similar. However, with static patterns, evidence of orientation discrimination by newborns was found if the infants were allowed to compare the habituated and novel orientations in a paired simultaneous comparison after habituation, but was not found when the habituated and novel stimulus were presented sequentially. The positive evidence of orientation discrimination in newborns supports the hypothesis that some form of orientationally tuned detectors can be used for discrimination of static patterns at birth. However, some developmental change over several weeks seems to be required before a positive electrophysiological VEP response can be measured for dynamic patterns changing in orientation.
‘Where’ and ‘What’ in Visual Search
Authors: Atkinson Janette , Braddick Oliver J
Published: January 2007

A line segment target can be detected among distractors of a different orientation by a fast ‘preattentive’ process. One view is that this depends on detection of a ‘feature gradient’, which enables subjects to locate where the target is without necessarily identifying what it is. An alternative view is that a target can be identified as distinctive in a particular ‘feature map’ without subjects knowing where it is in that map.

Experiments are reported in which briefly exposed arrays of line segments were followed by a pattern mask, and the threshold stimulus-mask interval determined for three tasks: ‘ what’—subjects reported whether the target was vertical or horizontal among oblique distractors; ‘ coarse where’—subjects reported whether the target was in the upper or lower half of the array; ‘ fine where’—subjects reported whether or not the target was in a set of four particular array positions. The threshold interval was significantly lower for the ‘coarse where’ than for the ‘what’ task, indicating that, even though localization in this task depends on the target's orientation difference, this localization is possible without absolute identification of target orientation. However, for the ‘fine where’ task, intervals as long as or longer than those for the ‘what’ task were required. It appears either that different localization processes work at different levels of resolution, or that a single localization process, independent of identification, can increase its resolution at the expense of processing speed. These possibilities are discussed in terms of distinct neural representations of the visual field and fixed or variable localization processes acting upon them.
Making Mayhew and Frisby Effortlessly Discriminable
Authors: Thompson Peter , Travis David
Published: January 2007

Mayhew and Frisby (1978) demonstrated that patterns which differ markedly in their spatial-frequency content may be very hard to discriminate. This they took as evidence against any model which proposes that the processes underlying texture discrimination have direct access to some local piecewise Fourier analysis of the patterns performed by spatial-frequency channels. It is shown that Mayhew and Frisby's patterns can be discriminated easily if their components have been incorporated into a pattern-contingent colour aftereffect. This demonstration suggests that the location in the visual pathway for contingent aftereffect adaptation must lie before the construction of the raw primal sketch, to which, according to Marr, we have conscious access. This location must also allow the orientation specificity seen in the aftereffect. This points to a locus in the striate cortex.
Emergence of Drawing Devices for Total and Partial Occlusion: A Longitudinal Study
Authors: Chen May Jane , Holman Jacqui
Published: January 2007

The developmental emergence of two drawing devices was investigated in young children: the use of omission (ie not drawing any of a hidden object) to depict total occlusion and the use of hidden line elimination (HLE, ie deleting only that part of an object that is hidden from view) to depict partial occlusion in a three-dimensional scene. Three groups of school children (5, 6, and 7 years old) were tested individually with two tasks four times over a 2-year period. One task called for the omission device (to draw a cup with its handle not in view) and the other for the HLE device (to draw one ball behind and partially occluded by another). The stimuli in each task were presented in pairs, with one member of the pair showing the occluded scene and the other a canonical or not-occluded scene. Changes in the strategies used by the children to indicate the visual differences within the pairs were recorded over the four testing sessions. Children were found to use the omission device more readily with the cup task than the HLE device with the ball task. There was an age-related trend in every task in the use of the drawing device appropriate to that task. For those who did not use the drawing device appropriate for a perspective drawing, there was a tendency for each age group to favour a particular strategy for representation. The advantage of using a longitudinal design to chart the developmental trend of the emergence of these two drawing devices is discussed.
Parts of Visual Objects: An Experimental Test of the Minima Rule
Authors: Braunstein Myron L , Hoffman Donald D , Saidpour Asad
Published: January 2007

Three experiments were conducted to test Hoffman and Richards's (1984) hypothesis that, for purposes of visual recognition, the human visual system divides three-dimensional shapes into parts at negative minima of curvature. In the first two experiments, subjects observed a simulated object (surface of revolution) rotating about a vertical axis, followed by a display of four alternative parts. They were asked to select a part that was from the object. Two of the four parts were divided at negative minima of curvature and two at positive maxima. When both a minima part and a maxima part from the object were presented on each trial (experiment 1), most of the correct responses were minima parts (101 versus 55). When only one part from the object—either a minima part or a maxima part—was shown on each trial (experiment 2), accuracy on trials with correct minima parts and correct maxima parts did not differ significantly. However, some subjects indicated that they reversed figure and ground, thereby changing maxima parts into minima parts. In experiment 3, subjects marked apparent part boundaries. 81% of these marks indicated minima parts, 10% of the marks indicated maxima parts, and 9% of the marks were at other positions. These results provide converging evidence, from two different methods, which supports Hoffman and Richards's minima rule.
The Rising Fastball: Baseball's Impossible Pitch
Authors: McBeath Michael K
Published: January 2007

Batters in professional baseball are confronted with pitches that appear to curve, dip, wobble, or rise. The rising fastball is a pitch where the ball appears to hop up as much as a third of a meter with a sudden increase in speed. Physics experiments confirm that many reported trajectories are possible, but not the rising fastball. The present paper shows how the apparent rise may be explained as a perceptual illusion due to the hitter underestimating original speed of the pitch.
Perspective, Orientation Disparity, and Anisotropy in Stereoscopic Slant Perception
Authors: Gillam Barbara , Ryan Colin
Published: January 2007

Stereoscopic depth estimates are not predictable from the geometry of point disparities. The configural properties of surfaces (surface contours) may play an important role in determining, for example, slant responses to a disparity gradient, and the marked anisotropy in favour of slant around a horizontal axis. It has been argued that variation in slant magnitude are attributable to the degree of perspective conflict present and that anisotropy is attributable to orientation disparity, which varies with the axis of slant. Three experiments were conducted in which configural properties were varied to try and tease apart the respective roles of orientation disparity and conflicting perspective in determining stereoscopic slant perception and slant axis anisotropy. The results could not be accounted for by the magnitude of the orientation disparities present. Conflicting perspective cues appeared to play a role but only for slant around a vertical axis. It was concluded that there are important configural effects in stereopsis attributable neither to orientation disparity nor to perspective.
Grouping Based on Phenomenal Similarity of Achromatic Color
Authors: Rock Irvin , Nijhawan Romi , Palmer Stephen , Tudor Leslie
Published: January 2007

It is widely acknowledged that a precondition for the perception of the world of objects and events is an early process of organization, and it has generally been assumed that such organization is based on the Gestalt laws of grouping. However, the stage at which such grouping occurs, whether early or late, is an empirical question. It is demonstrated in two experiments that grouping by similarity of neutral color is based not on similarity of absolute luminance at the level of the proximal stimulus, but on phenomenal similarity of lightness resulting from the achievement of lightness constancy. An alternative explanation of such grouping based on the equivalence of luminance ratios between elements and background is ruled out by appropriate control conditions.
Perceived Rigidity and Nonrigidity in the Kinetic Depth Effect
Authors: Ganis Giorgio , Casco Clara , Roncato Sergio
Published: January 2007

Stroboscopic simulations of three-dimensional rotating rigid structures can be perceived as highly nonrigid. To investigate this nonrigidity effect a sequence of either three (experiment 2 and 3) or thirty six frames (experiment 4) was used, each consisting of a set of dots with location on the horizontal axis corresponding to the parallel projection of a nominally defined helix. Observers were asked to judge the angle of rotation of eighty helices defined by the factorial combination of eight phase (φ) values (ie difference between the sinusoidal path of one dot and its neighbours) and ten different angular displacement values (α).

When in each static frame the dots can be organized into curved dotted line (small values of φ), the perceived 3-D helices are highly nonrigid. But when shape information is not available in each static frame (high values of φ), the helices are perceived as rigid and rotation judgement is possible providing that α < 15°. It appears that at small values of φ observers fail to recover the rigid structure of the helices since the input to the structure from the motion process may be distorted.
Accuracy and Consistency of Absolute Pitch
Authors: Wynn Vernon T
Published: January 2007

The accuracy and consistency of absolute pitch (AP) judgments have been measured on three subjects in two longitudinal studies separated by twenty years. The drifts and cyclical variations observed in the earlier study still persisted, and an investigation of two other subjects, one of whom was first studied forty years ago, suggests that they might undergo similar cyclical variations in their pitch perception. Pitch judgments also varied during the day. The detailed observations of these nonrandom fluctuations have been used to determine a value for the underlying consistency of the AP estimates. When the effects of the daytime variations and longer-term drifts were removed, the values for this consistency, as measured by the standard deviation, were calculated to be 3.1, 3.4, 3.7, 4.4, and 4.5 Hz for the five subjects. When an oscillator was used to produce the estimate, the consistency of the judgments was observed to depend on the accuracy of those judgments.
An Inquiry into Relational Concepts of Colour, Based on Incremental Principles of Colour Coding for Minimal Relational Stimuli
Authors: Mausfeld Rainer , Niederée Reinhard
Published: January 2007

Centre – surround stimuli evoke colour appearances (resembling surface colours) which cannot be produced by a single homogeneous spot of light alone (eg brown or grey). Although this seems of great impact to a general theory of colour (including ‘colour constancy’), the psychophysics of these ‘minimal relational stimuli’ is still less well understood than often assumed. On the basis of empirical as well as theoretical observations concerning centre– surround-type stimuli we introduce a relational model of colour coding. At the core of this model is the concept of a three-dimensional linear incremental colour code which behaves differently for increments and decrements. This model takes into account results on ‘discounting the background’ mechanisms and it is closely related to ratio-based relational concepts and to certain opponent-colour theories. In addition, it provides an analogue to the classical distinction between light and object colours, and covers colour appearances related to object colours as well. Within the conceptual framework offered, problems of complex colour perception (eg ‘colour constancy’) and judgmental modes are discussed. Conclusions regarding general limitations of three-dimensional modelling in colour perception are derived and corresponding refinements of the relational perspective are briefly outlined.
Asymmetries in the Sensitivity to Motion in Depth: A Centripetal Bias
Authors: Edwards Mark , Badcock David R
Published: January 2007

It is reasonable to ask whether observers are more sensitive to the pattern of image motion caused by forward locomotion through the environment than to the pattern caused by backward locomotion. The distribution of sensitivities of cells in MT does show such a bias, although this bias is minimal at small eccentricities. Additionally, both locomotion-induced stimulation and the sensitivities of MT cells suggest greater sensitivity should be obtained in the lower visual field.

Previous research on this issue has usually employed frontoparallel motion in patterns presented to one side of the fixation point. Both centrifugal and centripetal biases have been obtained. In this study the stimuli present motion signals that travel radially from (or towards) the fixation point. These stimuli, which produce a strong percept of motion in depth, are an adaptation of the global-dot-motion stimulus employed by Newsome and Pare. With these stimuli we find that sensitivity to motion in depth is greater in the lower visual field than in the upper visual field, and that sensitivity is greater to centripetal motion than to either centrifugal or frontoparallel motion. This centrifugal bias in sensitivity decreases with eccentricity. The last two findings contradict the notion that the bias is produced by the visual experience induced by normal forward locomotion and also that the detection of motion in depth is subserved by MT.
Faces and Facial Expressions do not Pop Out
Authors: Nothdurft Hans-Christoph
Published: January 2007

Subjects were asked to detect faces or facial expressions from patterns with a variable number of nonfaces or faces expressing different emotions. In most tests, reaction time was found to increase steeply with sample size, thus indicating serial-search characteristics for the patterns tested. There were, however, considerable differences in the slopes of the graphs (search time versus sample size), which could be attributed to visual (but not face) cues that are discriminated at similar speeds. Slopes did not change when patterns were presented upside down, although such a modification strongly affects the perception of faces and facial expressions.
Lightness Perception Can Be Affected by Surface Curvature from Stereopsis
Authors: Buckley David , Frisby John P , Freeman Jonathan
Published: January 2007

It is demonstrated that lightness perception can be affected by shape from stereopsis. The starting point was a report by Knill and Kersten that the perceived lightness of a monocularly viewed surface can be affected by outline-contour cues indicating that the surface is three-dimensional (3-D). In that study stimuli consisted of two equally sized abutting regions each having the same vertical linear-intensity ramp, so that the horizontal abutting boundary of the two patches created a sharp change in intensity. When this version of the Craik-O'Brien - Cornsweet stimulus has a rectangular outline, it exhibits the standard simultaneous contrast illusion: equivalent patches in the top and bottom regions appear to have different brightness despite having the same luminance. Knill and Kersten replicated this phenomenon with stimuli whose outline-contour cues were consistent with a flat (planar) surface. They found, however, that the illusion was greatly reduced in stimuli with outlines consistent with two abutting 3-D quarter cylinders, for which equivalent regions in the two halves appeared of similar lightness. Knill and Kersten interpreted this effect in terms of surface-lightness computations that took into account 3-D surface shape to achieve an integrated interpretation of the luminance and shape data. In the present report three experiments are described for which these earlier findings were taken as the starting point. In the first experiment the results were replicated by the use of a different methodology. In the second experiment it was shown that shape-from-stereo can produce similar effects on lightness perception to that caused by shape-from-contour. Real 3-D objects with curved surfaces, luminance profiles of the Knill and Kersten type, and carefully controlled outline-contour cues were used so that the objects appeared flat when viewed monocularly but curved in 3-D when seen binocularly. The third experiment was a control confirming that the stereo effect was not simply due to differences caused by monocular versus binocular viewing. It is concluded that the human visual system uses stereo cues, as well as outline-contour cues, in the interpretation of luminance data to recover surface lightness.
Estimation of Time to Vehicle Arrival—Effects of Age on Use of Available Visual Information
Authors: Hoffmann Errol R
Published: January 2007

Subjects estimated time of vehicle arrival while viewing twenty-four film clips of an approaching vehicle, half with a constant viewing time of 4.2 s and half with a constant vehicle-movement distance of 40 m. The distances from the subject at which the film ended were 20, 60, and 100 m. Speeds of approach varied between 7.45 and 15.44 ms−1. Performance was strongly dependent on age of the subject. Subjects in the 5-6-year-old group made estimates based on the distance of the vehicle; at 7 – 8 years an interaction between the effects of distance and velocity appeared and for 9–10-year-olds there was a main effect of the vehicle velocity. Only for adults was the information from distance and velocity fully integrated. There was no significant difference between males and females for any of the age groups. Performance of adults was very similar to that reported by other authors in that subjects underestimated the time to arrival of the vehicle, with estimated times about 60% of the actual times. Standard deviations of the estimated times were such that a small percentage of subjects overestimated times and hence would have caused a collision if they had proceeded with a crossing. The mechanism of time estimation was strongly dependent on the angular velocity of the vehicle subtended at the eye of the observer. This must exceed a threshold value of about 0.002 rad s_1 (adults) if a linear relationship between estimated and actual times is to be obtained.
Melodic Cues for Metre
Authors: Vos Piet G , van Dijk Arjan , Schomaker Lambert
Published: January 2007

A method of time-series analysis and a time-beating experiment were used to test the structural and perceptual validity of notated metre. Autocorrelation applied to the flow of melodic intervals between notes from thirty fragments of compositions for solo instruments by J S Bach strongly supported the validity of bar length specifications. Time-beating data, obtained with four stimuli from the same set, played in an expressionless mode, and presented under categorically distinct tempos to different subgroups of musically trained subjects, were rather inconsistent with respect to tapped bar lengths. However, taps were most frequently given to the events in the stimuli that corresponded with the first beats according to the score notations. No significant effects of tempo on tapping patterns were observed. The findings are discussed in comparison with other examinations of metre inference from musical compositions.