平滑运动条件下的图形颜色及形状加工特性的研究

本研究对在运动图形识别过程中,有关图形的不同特征（颜色、形状等）的加工特性、方向性效应以及不同空间位置（或时间间隔）对图形识别的影响了探讨。结果发现,视觉系统在运动信息加工时,对目标的不同特征的加工存在不均衡性,加工的难度有差异。颜色的加工难度要比形状的加工难度小。视觉系统对不同运动方向上的图形匹配反应特性也存在差异,图形匹配过程受时间或距离因素的影响,匹配的反应时随着两个比较图形之间的空间距离的增加而减少。     

Independent, synchronous access to color and motion features

We investigated the role of attention in pairing superimposed visual features. When moving dots alternate in color and in motion direction, reports of the perceived color and motion reveal an asynchrony: the most accurate reports occur when the motion change precedes the associated color change by approximately 100ms [Moutoussis, K., & Zeki, S. (1997). A direct demonstration of perceptual asynchrony in vision. Proceedings of the Royal Society of London B, 264, 393-399]. This feature binding asynchrony was probed by manipulating endogenous and exogenous attention. First, endogenous attention was manipulated by changing which feature dimension observers were instructed to attend to first. This yielded little effect on the asynchrony. Second, exogenous attention was manipulated by briefly presenting a ring around the target, cueing the report of the color and motion seen within the ring. This reduced or eliminated the apparent latency difference between color and motion. Accuracy was best predicted by timing of each feature relative to the cue rather than the timing of the two features relative to each other, suggesting independent attentional access to the two features with an exogenous attention cue. The timing of attentional cueing affected feature pairing reports as much as the timing of the features themselves.     

Children's attention to stimulus components with variation in relative salience of components and degree of stimulus integration

A total of 400 children at ages 5, 9, and 12 years were given a component selection task with stimuli differing in color and shape. Relative salience of these two stimulus components was manipulated across subjects in two ways: the standard shapes and colors from previous studies were compared with standard shapes in fluorescent colors, and the latter materials were compared with nonsense shapes in fluorescent colors. While fluorescence of color had little effect, the replacement of standard shapes with nonsense figures caused attention to be redirected from shape to color as the primary cue for learning. This effect was more pronounced at age 9 than at age 5. Apparently there is a greater tendency for older than for younger children to withdraw attention from a normally dominant component such as shape, when it is advantageous to adopt another feature such as color as the primary functional cue. An additional variable was integration of components (color within shape vs color as background for shape). Integration produced generally greater attention to color but did not affect the general pattern of salience effects.     

The nature of cross-modal color-word interference effects

Cowan and Barron (1987) and Cowan (1989b) reported that color-naming performance was slowed by spoken color names drawn from the same set but presented in an order unrelated to the printed colors. Although Miles, Madden, and Jones (1989) and Miles and Jones (1989) were unable to replicate this cross-modal effect, it is replicated here in two experiments with much better experimental control than before. However, the effect is shown to depend upon the relative timing of the color and word in a way that conflicts with the theoretical account that Cowan and Barron offered. While Cowan and Barron suggested that an irrelevant color word would contaminate the response set if this word occupied short-term memory when the color was about to be named, it appears that interference actually occurs only if the memory representation was formed very recently and had not been inhibited. Further implications for processing are discussed.     

Retrospective cues based on object features improve visual working memory performance in older adults

Research with younger adults has shown that retrospective cues can be used to orient top-down attention toward relevant items in working memory. We examined whether older adults could take advantage of these cues to improve memory performance. Younger and older adults were presented with visual arrays of five colored shapes; during maintenance, participants were presented either with an informative cue based on an object feature (here, object shape or color) that would be probed, or with an uninformative, neutral cue. Although older adults were less accurate overall, both age groups benefited from the presentation of an informative, feature-based cue relative to a neutral cue. Surprisingly, we also observed differences in the effectiveness of shape versus color cues and their effects upon post-cue memory load. These results suggest that older adults can use top-down attention to remove irrelevant items from visual working memory, provided that task-relevant features function as cues.     

Distinctive shapes benefit short-term memory for color associations, but not for color

In four experiments, we examined the effect of pairing colors with either homogeneous or heterogeneous shapes on a short-term memory task. In Experiment 1, we found no differences in color memory for displays in which colors were each associated with different shapes, paired with individual homogeneous shapes, or paired with heterogeneous shapes. In contrast, in Experiment 2, we found that when participants were asked to remember the specific pairings of colors, memory was improved for heterogeneous-shape displays. The benefit for heterogeneous shapes appears to be memorial, rather than one that occurs at the time of encoding (Experiment 3) or retrieval (Experiment 4). The present study suggests that distinctive shapes can be used to help bind color associations in visual short-term memory.     

How chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>) perform in a modified emotional Stroop task

The emotional Stroop task is an experimental paradigm developed to study the relationship between emotion and cognition. Human participants required to identify the color of words typically respond more slowly to negative than to neutral words (emotional Stroop effect). Here we investigated whether chimpanzees (Pan troglodytes) would show a comparable effect. Using a touch screen, eight chimpanzees were trained to choose between two simultaneously presented stimuli based on color (two identical images with differently colored frames). In Experiment 1, the images within the color frames were shapes that were either of the same color as the surrounding frame or of the alternative color. Subjects made fewer errors and responded faster when shapes were of the same color as the frame surrounding them than when they were not, evidencing that embedded images affected target selection. Experiment 2, a modified version of the emotional Stroop task, presented subjects with four different categories of novel images: three categories of pictures of humans (veterinarian, caretaker, and stranger), and control stimuli showing a white square. Because visits by the veterinarian that include anaesthetization can be stressful for subjects, we expected impaired performance in trials presenting images of the veterinarian. For the first session, we found correct responses to be indeed slower in trials of this category. This effect was more pronounced for subjects whose last anaesthetization experience was more recent, indicating that emotional valence caused the slowdown. We propose our modified emotional Stroop task as a simple method to explore which emotional stimuli affect cognitive performance in nonhuman primates.     

Constructing and representing visual objects

The objects we see are not given in the images at the eyes, but must be constructed by the human visual system. Indeed, damage to specific brain regions often leads to specific impairments of visual abilities (for example, the perception of shape, color or motion). Human vision constructs the various properties of visual objects, not independently of each other, but in a highly coordinated fashion. The construction of one visual property strongly influences the constructions of other properties. Visual shape is an important construction for successfully recognizing objects. There is growing consensus that human vision represents shapes in terms of component parts and their spatial relationships. These parts and their spatial relationships provide a powerful first index into one's visual memory of shapes.     

Presence and absence of color selectivity in the motion aftereffect

It is controversial whether the magnitude of the motion aftereffect is greater when both inspection and test stimuli are the same color rather than different colors (color selectivity). The present experiments show that the extent of color selectivity in the classical motion aftereffect depends upon (1) the duration of the interval between inspection and test, and (2) the nature of the stimulation during this interval. These findings are consistent with previous reports of two phases in the motion aftereffect and are interpreted in terms of the known properties of sustained and transient cells in the human visual system.     

The spacing illusion: a spatial aperture problem?

A geometrical illusion in which the horizontal spacing between adjacent parallel lines in a row is underestimated when the lines are tilted away from vertical in a chevron configuration was investigated in two experiments. The perceived spacing was found to decrease as the tilt angle increased, consistent with the idea that separation judgements are influenced by the normal spacing between lines ie at right angles to the line orientation. It is proposed that this illusion reveals an analogue in spatial perception to the well-known aperture problem in motion perception. In establishing the separation of nearby or overlapping shapes in an image, the visual system cannot only rely upon the normal separation of contours belonging to each shape (as would be visible through small spatial apertures or receptive fields), since this varies with contour orientation. The system is therefore faced with a spatial aperture problem. The spacing illusion may arise because information usually available to solve the problem is absent in the illusion figure, or it may reflect a bias in favour of the orthogonal, which is adopted in the face of the ambiguity.     

Developmental course of the temporal relationship between gaze direction and vocal production in typical and Down's syndrome infants

This study was aimed at examining the temporal relationship between gaze and vocal production behaviour among typically developing infants, infants with Down's syndrome, and their mothers. If gaze–voice timing behaviour is an organizing principle of communicative interaction in typical population, then studying it should provide insight into how children with Down's syndrome and their mothers use this temporal relationship to structure their exchanges. Forty-four mother–infant dyads (22 dyads with a Down's syndrome child and 22 with a typical child) were observed. The developmental course of timing pattern was not different between DS and typically developing infants from 4 to 19 months (DA). Insofar as the timing patterns differed between DS and typical infants at 20 months, this could be explained by their differing level of language acquisition. With the use of language, the timing patterns will reappear equal in the both populations. Results suggest that (i) the children's behaviours could be partially explained by the behaviours of their mothers. The mother–child dyad would be the mould that shapes the child's future sociolinguistic skills, and (ii) for the two populations, the timing-pattern changes could be explained by the emergence of language.     

Visual training improves perceptual grouping based on basic stimulus features

Training on visual tasks improves performance on basic and higher order visual capacities. Such improvement has been linked to changes in connectivity among mediating neurons. We investigated whether training effects occur for perceptual grouping. It was hypothesized that repeated engagement of integration mechanisms would enhance grouping processes. Thirty-six participants underwent 15 sessions of training on a visual discrimination task that required perceptual grouping. Participants viewed 20?×?20 arrays of dots or Gabor patches and indicated whether the array appeared grouped as vertical or horizontal lines. Across trials stimuli became progressively disorganized, contingent upon successful discrimination. Four visual dimensions were examined, in which grouping was based on similarity in luminance, color, orientation, and motion. Psychophysical thresholds of grouping were assessed before and after training. Results indicate that performance in all four dimensions improved with training. Training on a control condition, which paralleled the discrimination task but without a grouping component, produced no improvement. In addition, training on only the luminance and orientation dimensions improved performance for those conditions as well as for grouping by color, on which training had not occurred. However, improvement from partial training did not generalize to motion. Results demonstrate that a training protocol emphasizing stimulus integration enhanced perceptual grouping. Results suggest that neural mechanisms mediating grouping by common luminance and/or orientation contribute to those mediating grouping by color but do not share resources for grouping by common motion. Results are consistent with theories of perceptual learning emphasizing plasticity in early visual processing regions.     

Perceptual asynchronies between color and motion at the onset of motion and along the motion trajectory

A color change that is physically simultaneous with the onset of object motion may be perceived as occurring before the initial displacement. In contrast, a colored flash during object motion is displaced in the direction of motion, suggesting that it is perceived after the continuous position change. The aim of our study was to reconcile these apparently conflicting results. To this end, we reexamined color-motion asynchronies as a function of trajectory position. Our results indicate that an abrupt color change lags object motion along the trajectory, but no asynchrony was found when the abrupt color change occurred at motion onset. Even if the lag of color relative to motion decreased with increasing object size, we did not replicate a lag of motion relative to color in any of our experiments. Furthermore, judgments at motion onset were not correlated with judgments along the trajectory, suggesting that the underlying mechanisms or task demands were different. Temporal order may be judged at motion onset, whereas position is judged during ongoing motion.     

Lack of color integration in visual short-term memory binding

Bicolored objects are retained in visual short-term memory (VSTM) less efficiently than unicolored objects. This is unlike shape–color combinations, whose retention in VSTM does not differ from that observed for shapes only. It is debated whether this is due to a lack of color integration and whether this may reflect the function of separate memory mechanisms. Participants judged whether the colors of bicolored objects (each with an external and an internalcolor) were the same or different across two consecutive screens. Colors had to be remembered either individually or in combination. In Experiment 1, external colors in the combined colors condition were remembered better than the internal colors, and performance for both was worse than that in the individual colors condition. The lack of color integration observed in Experiment 1 was further supported by a reduced capacity of VSTM to retain color combinations, relative to individual colors (Experiment 2). An additional account was found in Experiment 3, which showed spared color–color binding in the presence of impaired shape–color binding in a brain-damaged patient, thus suggesting that these two memory mechanisms are different.     

Priming of luminance-defined motion direction in visual search

Features that we have recently attended to strongly influence how we allocate visual attention across a subsequently viewed visual scene. Here, we investigate the characteristics of any such repetition effects during visual search for Gabor patch targets drifting in the odd direction relative to a set of distractors. The results indicate that repetition of motion direction has a strong effect upon subsequent allocation of attention. This was the case for judgments of a target’s presence or absence, of a target’s location, and of the color of a target drifting in the odd direction. Furthermore, distractor repetition on its own can facilitate search performance on subsequent trials, indicating that the benefits of repetition of motion direction are not confined to repetition of target features. We also show that motion direction need not be the target-defining dimension throughout a trial block for motion priming to occur, but that priming can build up with only one presentation of a given target direction, even within blocks of trials where the target may, unpredictably, be defined by a different feature (color, in this case), showing that dimensional-weighting accounts cannot, on their own, account for motion direction priming patterns. Finally, we show by randomizing the set size between trials that priming of motion direction can decrease search rates in visual search.     

Lack of free choice reveals the cost of multiple-target search within and across feature dimensions

Having to look for multiple targets typically results in switch costs. However, using a gaze-contingent eyetracking paradigm with multiple color-defined targets, we have recently shown that the emergence of switch costs depends on whether observers can choose a target or a target is being imposed upon them. Here, using a similar paradigm, we tested whether these findings generalize to the situation in which targets are specified across different feature dimensions. We instructed participants to simultaneously search for, and then fixate, either of two possible targets presented among distractors. The targets were defined as either two colors, two shapes, or one color and one shape. In one condition, only one of the two targets was available in each display, so that the choice was imposed. In the other condition, both targets would be present in each display, which gave observers free choice over what to search for. Consistent with our earlier findings, switch costs emerged when targets were imposed, whereas no switch costs emerged when target selection was free, irrespective of the dimension in which the targets were defined. The results are consistent with the operation of different modes of control in multiple-target search, with switch costs emerging whenever reactive control is required and being reduced or absent when displays allow for proactive control.     

Cognitive and linguistic factors affect visual feature integration

Five experiments investigated the influence of cognitive and linguistic factors on the integration of color and letter-shape information. Subjects were briefly presented strings of colored letters that varied in pronounceability and familiarity. Detection and search tasks required subjects to identify the color of predesignated target letters. It was proposed that errors in integrating color and shape would be less likely with items from different perceptual units than from items within the same perceptual unit. If words, at some level of perceptual analysis, are processed as units whereas nonwords are processed by individual letters, then there should be more letter-shape and color feature integration errors with words than with nonwords. The first two experiments tested this prediction by comparing feature integration errors with words and nonwords. The remaining experiments manipulated letter-string pronounceability, familiarity, and the presence of vowels to isolate the factors that may influence feature integration. The results demonstrate that cognitive and linguistic factors, such as familiarity and pronounceability, can influence the combination of colors and shapes in perception.     

Sequential and Biomechanical Factors Constrain Timing and Motion in Tapping

The authors examined how timing accuracy in tapping sequences is influenced by sequential effects of preceding finger movements and biomechanical interdependencies among fingers. Skilled pianists tapped sequences at 3 rates; in each sequence, a finger whose motion was more or less independent of other fingers' motion was preceded by a finger to which it was more or less coupled. Less independent fingers and those preceded by a more coupled finger showed large timing errors and change in motion because of the preceding finger's motion. Motion change correlated with shorter intertap intervals and increased with rate. Thus, timing of sequence elements is not independent of the motion trajectories that individuals use to produce them. Neither motion nor its relation to timing is invariant across rates.     

Human preferences are biased towards associative information

There is ample evidence that the brain generates predictions that help interpret sensory input. To build such predictions the brain capitalizes upon learned statistical regularities and associations (e.g., “A” is followed by “B”; “C” appears together with “D”). The centrality of predictions to mental activities gave rise to the hypothesis that associative information with predictive value is perceived as intrinsically valuable. Such value would ensure that this information is proactively searched for, thereby promoting certainty and stability in our environment. We therefore tested here whether, all else being equal, participants would prefer stimuli that contained more rather than less associative information. In Experiments 1 and 2 we used novel, meaningless visual shapes and showed that participants preferred associative shapes over shapes that had not been associated with other shapes during training. In Experiment 3 we used pictures of real-world objects and again demonstrated a preference for stimuli that elicit stronger associations. These results support our proposal that predictive information is affectively tagged, and enhance our understanding of the formation of everyday preferences.     

Synchronous change and perception of object unity: evidence from adults and infants.

Adults and infants display a robust ability to perceive the unity of a center-occluded object when the visible ends of the object undergo common motion (e.g. Kellman, P.J., Spelke, E.S., 1983. Perception of partly occluded objects in infancy. Cognitive Psychology 15, 483-524). Ecologically oriented accounts of this ability focus on the primary of motion in the perception of segregated objects, but Gestalt theory suggests a broader possibility: observers may perceive object unity by detecting patterns of synchronous change, of which common motion is a special case. We investigated this possibility with observations of adults and 4-month-old infants. Participants viewed a center-occluded object whose visible surfaces were either misaligned or aligned, stationary or moving, and unchanging or synchronously changing in color or brightness in various temporal patterns (e.g. flashing). Both alignment and common motion contributed to adults' perception of object unity, but synchronous color changes did not. For infants, motion was an important determinant of object unity, but other synchronous changes and edge alignment were not. When a stationary object with aligned edges underwent synchronous changes in color or brightness, infants showed high levels of attention to the object, but their perception of its unity appeared to be indeterminate. An inherent preference for fast over slow flash rates, and a novelty preference elicited by a change in rate, both indicated that infants detected the synchronous changes, although they failed to use them as information for object unity. These findings favor ecologically oriented accounts of object perception in which surface motion plays a privileged role.