Parametric induction of animacy experience

Graphical displays of simple moving geometrical figures have been repeatedly used to study the attribution of animacy in human observers. Yet little is known about the relevant movement characteristics responsible for this experience. The present study introduces a novel parametric research paradigm, which allows for the experimental control of specific motion parameters and a predictable influence on the attribution of animacy. Two experiments were conducted using 3D computer animations of one or two objects systematically introducing variations in the following aspects of motion: directionality, discontinuity and responsiveness. Both experiments further varied temporal kinematics. Results showed that animacy experience increased with the time a moving object paused in the vicinity of a second object and with increasing complexity of interaction between the objects (approach and responsiveness). The experience of animacy could be successfully modulated in a parametric fashion by the systematic variation of comparably simple differential movement characteristics.     

相对到达时间任务中飞行员对客体特征与运动特征的分离

相对到达时间任务(RAT)是判断两个运动客体哪个先到达指定目标, 可用来评估个体动态空间能力。采用RAT任务对飞行员与普通被试进行对照研究, 寻求发现两组在运动客体特征和视觉空间运动特征及其相互关系上的处理差异。设计了3个实验分别考察客体颜色、客体大小、运动方向、速率大小、视线方向以及背景特征对判断的影响。结果显示：(1)客体颜色不影响运动客体的相对时间判断, 客体大小、运动方向、速率大小、视线方向以及背景特征影响判断; (2)控制组对显示屏上从左到右的运动客体的相对时间判断好于从右到左任务, 大速率任务判断更好, 对大客体快速行驶而小客体低速行驶时的相对到达时间更易区分, 且与两眼视线方向不一致的运动方向会使控制组判断更难, 运动背景中的目标线特征改变使控制组判断绩效降低; (3)和控制组比, 飞行员反应快正确率高, 其快速判断优势集中体现在从右到左运动以及小速率任务上, 且在不同运动方向和不同速率上的反应时均无差异, 飞行员的处理优势还表现在不受客体大小、视线方向改变和目标线特征改变的影响。结论：飞行员能在变化的空间中准确处理相对速度、相对距离、相对时间等运动信息, 能分离客体大小、背景、运动方向等因素对相对到达时间判断的影响, 在运动空间中飞行员具有较高场独立性认知特征和动态空间处理能力。     

Giving Meaning to Movement: A Developmental Study

Recently, researchers have been investigating the effects of kinematics stimulus properties on pattern perception and recognition. However, the stimulus properties that are used to discriminate animate from inanimate objects have received relatively little attention. Earlier research has indicated that the external movement of artificially generated objects is perceived as animate by observers of all ages. In this investigation, children in Grades 1,4, and 7 and university adults were asked to describe what they saw after viewing computer-generated displays of two circular objects that exhibited variations of external and internal movement. We predicted that observers would incorporate and integrate the salient kinematic properties of the objects in a display into a coherent narrative and that their ability to achieve matches among the properties of objects in a display and the properties of objects described in the narrative would increase with age. Moreover, because of their relative insensitivity to the actual properties of objects in the display, we predicted that younger observers would make more animate attributions for nonmoving objects and fewer animate attributions for moving objects than would older observers. The result supported these predictions.     

Infants' ability to use luminance information to individuate objects

Recent research indicates that infants first use form and then surface features as the basis for individuating objects. However, very little is known about the underlying basis for infants' differential sensitivity to form than surface features. The present research assessed infants' sensitivity to luminance differences. Like other surface properties, luminance information typically reveals little about an object. Unlike other surface properties (e.g. pattern, color), the visual system can detect luminance differences at birth. The outcome of two experiments indicated that 11.5-month-olds, but not 7.5-month-olds, used luminance differences to individuate objects. These results suggest that it is not the age at which infants can detect a feature, but the nature of the information carried by the feature, that determines infants' capacity to individuate objects.     

Features derived from first-order motion mechanisms predict anomalies in motion perception

Current dominant hypotheses of how humans detect the movement of patterns assume that the pattern is divided into one-dimensional sinusoidally varying luminance patterns, referred to as gratings (first-order components). The speed of these gratings is independently encoded from predominantly spatial and temporal frequency information, and their direction is encoded from orientation information. This paper addresses the problem of how the individually encoded grating information is combined to give perceived pattern direction, given that real moving objects are generally made up of more than one component. More specifically, further evidence is presented for a combination based on the use of a feature derived from first-order components--'first-order feature hypothesis'. This hypothesis essentially implements a constraint on pattern direction called the intersection of constraints (IOC) proposed by Adelson and Movshon [1982, Nature 300 523-525]. A simulation of the model is used to make three new predictions about a perceived motion reversal reported by Derrington et al (1992, Vision Research 32 699-707); these predictions are tested and found to be consistent with the first-order feature hypothesis.     

Hue shift of induced colour as a function of luminance relations

The hue of induced colour was studied as a function of surround/test field luminance ratio using a chromatic surround and an achromatic central test field. The hue of the test field was determined by means of colour naming methods. Three inducing colours were used: blue (Wr No. 47), green (Wr No. 58), and red (Wr No. 25). The number of subjects was 9–11 in the two experiments. The luminance ratio (ranging from 0.07 to 17.1) was varied by varying the luminance of the test field (Experiment 1) or of the surround (Experiment 2). For the blue surround the results show a hue shift in accordance with the Bezold-Brücke phenomenon. For the inducing colours green and red the induced colours are weak, and the hue shifts are more or less unsystematic though there are individual subjects showing a trend in the Bezold-Brücke direction. It is concluded that the hue shifts depend on the luminance relations rather than on the test field luminance.     

Motion aftereffect of combined first-order and second-order motion

When, after prolonged viewing of a moving stimulus, a stationary (test) pattern is presented to an observer, this results in an illusory movement in the direction opposite to the adapting motion. Typically, this motion aftereffect (MAE) does not occur after adaptation to a second-order motion stimulus (i.e. an equiluminous stimulus where the movement is defined by a contrast or texture border, not by a luminance border). However, a MAE of second-order motion is perceived when, instead of a static test pattern, a dynamic test pattern is used. Here, we investigate whether a second-order motion stimulus does affect the MAE on a static test pattern (sMAE), when second-order motion is presented in combination with first-order motion during adaptation. The results show that this is indeed the case. Although the second-order motion stimulus is too weak to produce a convincing sMAE on its own, its influence on the sMAE is of equal strength to that of the first-order motion component, when they are adapted to simultaneously. The results suggest that the perceptual appearance of the sMAE originates from the site where first-order and second-order motion are integrated.     

The perceived intentionality of groups.

Heider and Simmel [Heider, F., Simmel, M., 1944. An experimental study of apparent behavior. American Journal of Psychology 57, 243-259] found that people spontaneously describe depictions of simple moving objects in terms of purposeful and intentional action. Not all intentional beings are objects, however, and people often attribute purposeful activity to non-object individuals such as countries, basketball teams, and families. This raises the question of whether the same effect found by Heider and Simmel would hold for non-object individuals such as groups. We replicate and extend the original study, using both objects and groups as stimuli, and introducing two control conditions with groups that are not engaged in structured movement. We found that under the condition that best promoted the attribution of intentionality, moving groups are viewed as purposeful and goal-directed entities to the same extent that moving objects are. These results suggest that the psychological distinction between the notion of 'intentional entity' and the notion of 'object' can be found even in the perception of moving geometrical figures.     

Luminance thresholds for the Bezold-Brücke hue shift

This study presents data on the luminance difference at which a hue difference is first perceived between two identical spectral lights. Thresholds were obtained for both luminance increments and decrements from a 2.00 log troland standard for wavelengths between 470 nm and 690 nm. A predicted luminance threshold for each wavelength was calculated based on wavelength discrimination data and the Purdy constant hue contours; i.e. that luminance at which the constant hue contour intersects the wavelength discrimination bound for a given wavelength. A generally good agreement was obtained between observed and predicted values.     

Perception of animacy from the motion of a single object

We demonstrate that a single moving object can create the subjective impression that it is alive, based solely on its pattern of movement. Our displays differ from conventional biological motion displays (which normally involve multiple moving points, usually integrated to suggest a human form) in that they contain only a single rigid object moving across a uniform field. We focus on motion paths in which the speed and direction of the target object change simultaneously. Naive subjects' ratings of animacy were significantly influenced by (i) the magnitude of the speed change, (ii) the angular magnitude of the direction change, (iii) the shape of the object, and (iv) the alignment between the principal axis of the object and its direction of motion. These findings are consistent with the hypothesis that observers classify as animate only those objects whose motion trajectories are otherwise unlikely to occur in the observed setting.     

Character movement and the representation of space during narrative comprehension

Traditional research on situation models has examined the accessibility of locations and objects during narrative experiences. These studies have described a ubiquitous gradient effect: Spatial locations and objects in reader focus are more accessible than locations farther from this focus, with accessibility decreasing as a function of distance. How might readers’ expectations about character movement, beyond information about spatial locations, additionally affect this accessibility gradient? In two experiments, we investigated whether reader expectations for character movement impact the accessibility of spatial information from memory. In Experiment 1, participants read stories that described characters moving in either a unidirectional or a random pattern through a learned environment. In Experiment 2, characters moved forward in a unidirectional way or backtracked through previously explored rooms. The results suggest that reader expectations for character movement can influence the accessibility of spatial information. Such expectations play a critical role in processes of narrative comprehension.     

The pop out of scene-relative object movement against retinal motion due to self-movement

An object that moves is spotted almost effortlessly; it "pops out". When the observer is stationary, a moving object is uniquely identified by retinal motion. This is not so when the observer is also moving; as the eye travels through space all scene objects change position relative to the eye producing a complicated field of retinal motion. Without the unique identifier of retinal motion an object moving relative to the scene should be difficult to locate. Using a search task, we investigated this proposition. Computer-rendered objects were moved and transformed in a manner consistent with movement of the observer. Despite the complex pattern of retinal motion, objects moving relative to the scene were found to pop out. We suggest the brain uses its sensitivity to optic flow to "stabilise" the scene, allowing the scene-relative movement of an object to be identified.     

Salience from multiple feature contrast: Evidence from saccade trajectories

We used eye tracking to quantify the extent to which combinations of salient contrasts (orientation, luminance, and movement) influence a central salience map that guides eye movements. We found that luminance combined additively with orientation and movement, suggesting that the salience system processes luminance somewhat independently of the two other features. On the other hand, orientation and movement together influenced salience underadditively, suggesting that these two features are processed nonindependently. This pattern of results suggests that the visual system does not sum sources of salience linearly, but treats some sources of salience as redundant.

     

The emergence of kind-based object individuation in infancy

Four experiments investigated whether 12-month-old infants use perceptual property information in a complex object individuation task, using the violation-of-expectancy looking time method (Xu, 2002; Xu & Carey, 1996). Infants were shown two objects with different properties emerge and return behind an occluder, one at a time. The occluder was then removed, revealing either two objects (expected outcome, if property differences support individuation) or one object (unexpected outcome). In Experiments 1-3, infants failed to use color, size, or a combination of color, size, and pattern differences to establish a representation of two distinct objects behind an occluder. In Experiment 4, infants succeeded in using cross-basic-level-kind shape differences to establish a representation of two objects but failed to do so using within-basic-level-kind shape differences. Control conditions found that the methods were sensitive. Infants succeeded when provided unambiguous spatiotemporal information for two objects, and they encoded the property differences during these experiments. These findings suggest that by 12 months, different properties play different roles in a complex object individuation task. Certain salient shape differences enter into the computation of numerical distinctness of objects before other property differences such as color or size. Since shape differences are often correlated with object kind differences, these results converge with others in the literature that suggest that by the end of the first year of life, infants' representational systems begin to distinguish kinds and properties.     

Discriminability of brightness change for infants

Four-month-old human infants who were habituated to a 490-nm stimulus of 3.5 cd · m^?2 luminance did not show recovery when the stimulus was increased or decreased in luminance by a factor of 2 but not changed in hue. A fourfold luminance increase produced a recovery in looking time. When compared with earlier results on simultaneous discrimination of brightness change, the results imply that infants differ from adults more in ability to code or retrieve than in ability to detect intensive differences. The implication is further supported by the differentiating response of infants to changes in hue.     

Colour changes as a function of luminance contrast.

When spectral light increases in luminance, the hues change. Normally, long-wavelength light becomes increasingly yellow, and short-wavelength light turns blue or blue-green. This is known as the Bezold-Brücke hue shift. Less notice has been paid to the change in relative chromatic content (saturation or chromatic strength) that accompanies these shifts in hue. As luminance contrast increases from zero, chromatic strength increases to reach a maximum at a luminance that is wavelength dependent. Short-wavelength blueish light reaches this maximum at low relative luminances, whereas midspectral yellowish stimuli need several log units higher luminance. Red and green are somewhere in between. For luminances above this maximum, the chromatic content usually diminishes, and most light becomes more whitish in appearance. In this study it is demonstrated how the combined chromatic appearance of hue and chromatic strength change with intensity. Both phenomena find a common physiological interpretation in the nonlinear and nonmonotonic responses of colour-opponent P cells in the retina and lateral geniculate nucleus of the primate. A model that combines the outputs of six P-cell types accounts for observers' estimates of hue and chromatic strength.     

Individuation of visual objects over time

How does an observer decide that a particular object viewed at one time is actually the same object as one viewed at a different time? We explored this question using an experimental task in which an observer views two objects as they simultaneously approach an occluder, disappear behind the occluder, and re-emerge from behind the occluder, having switched paths. In this situation the observer either sees both objects continue straight behind the occluder (called "streaming") or sees them collide with each other and switch directions ("bouncing"). This task has been studied in the literature on motion perception, where interest has centered on manipulating spatiotemporal aspects of the motion paths (e.g. velocity, acceleration). Here we instead focus on featural properties (size, luminance, and shape) of the objects. We studied the way degrees and types of featural dissimilarity between the two objects influence the percept of bouncing vs. streaming. When there is no featural difference, the preference for straight motion paths dominates, and streaming is usually seen. But when featural differences increase, the preponderance of bounce responses increases. That is, subjects prefer the motion trajectory in which each continuously existing individual object trajectory contains minimal featural change. Under this model, the data reveal in detail exactly what magnitudes of each type of featural change subjects implicitly regard as reasonably consistent with a continuously existing object. This suggests a simple mathematical definition of "individual object:" an object is a path through feature-trajectory space that minimizes feature change, or, more succinctly, an object is a geodesic in Mahalanobis feature space.     

Colour vision brings clarity to shadows

We have revealed a new role for colour vision in visual scene analysis: colour vision facilitates shadow identification. Shadows are important features of the visual scene, providing information about the shape, depth, and movement of objects. To be useful for perception, however, shadows must be distinguished from other types of luminance variation, principally the variation in object reflectance. A potential cue for distinguishing shadows from reflectance variations is colour, since chromatic changes typically occur at object but not shadow boundaries. We tested whether colour cues were exploited by the visual system for shadow identification, by comparing the ability of human test subjects to identify simulated shadows on chromatically variegated versus achromatically variegated backgrounds with identical luminance compositions. Performance was superior with the chromatically variegated backgrounds. Furthermore, introducing random colour contrast across the shadow boundaries degraded their identification. These findings demonstrate that the visual system exploits inbuilt assumptions about the relationships between colour and luminance in the natural visual world.     

Higher-order factors influencing the perception of sliding and coherence of a plaid.

The effect of several new stimulus parameters on the perception of a moving plaid pattern (the sum of two sine-wave gratings) were tested. It was found that: (i) the degree of perceived sliding is strongly influenced by the aperture configuration through which the plaid is viewed; (ii) the chromaticity of the sinusoidal components affects coherence in that more sliding is observed when the plaid components differ in hue, and there is less sliding when they are of the same hue; (iii) equiluminant plaids made of components equal in color almost never show any sliding; and (iv) sliding increases with viewing time. The coherence-sliding percept must therefore be influenced by color, by global interactions, and by adaptation or learning effects, thus suggesting a higher-level influence. These results are most easily modelled by separating the decision to carry out recombination from the process of recombination.     

Perceiving curvilinear heading in the presence of moving objects

Four experiments were directed at understanding the influence of multiple moving objects on curvilinear (i.e., circular and elliptical) heading perception. Displays simulated observer movement over a ground plane in the presence of moving objects depicted as transparent, opaque, or black cubes. Objects either moved parallel to or intersected the observer's path and either retreated from or approached the moving observer. Heading judgments were accurate and consistent across all conditions. The significance of these results for computational models of heading perception and for information in the global optic flow field about observer and object motion is discussed.