The role of eye height in perceiving affordances and object dimensions

In four experiments on perceived object height and width, the effects of shifting participants’ effective eye height (EEH) on affordance (intrinsic) and apparent size (extrinsic) judgments were con-trasted. In Experiment 1, EEH shifts produced comparable overestimations ofheight in intrinsic and extrinsic tasks. A similar result was found with a more abstract extrinsic height task (Experiment 2). However, Experiment 3 revealed a dissociation between intrinsic and extrinsic tasks of perceivedwidth. Affordance judgments were affected by EEH shifts, whereas apparent size judgments were not. Experiment 4 compared participants’ performance on comparable extrinsic tasks of height and width. Height judgments were affected by EEH shifts, but width judgments were again unaffected. It is concluded that eye height may be a more natural metric for object height than for width. Moreover, this difference reflects a basic flexibility within the human visual system for selectively attuning to the most accessible sources of size information.     

Using eye height in different postures to scale the heights of objects

Four experiments examined eye height (EH) scaling of object height across different postures. In Experiment 1, participants viewed rectangular targets while they were standing, seated, and prone. Standing and seated judgments were similar, possibly due to EH scaling. Prone judgments were significantly lower, a result not attributable to the unfamiliarity of that posture (Experiment 2). In Experiment 3, shifts of seated EH produced height overestimations equivalent to those of standing viewers. Experiment 4 examined the visual salience of size information in the seated and prone judgments by holding EH constant and manipulating another source: linear perspective. Participants viewed targets placed on true- and false-perspective (FP) gradients. The FP gradient affected prone judgments but not seated judgments, which presumably relied on EH. It appears that the human visual system weights size information differentially depending on its utility.     

Spatial judgments of exocentric extents in an open-field situation: familiar versus unfamiliar size.

Carlson and Tassone (1971) found that an object of familiar size presented in an outdoor setting and viewed at an appreciable distance is judged to be more distant than an unfamiliar object. Three experiments examined whether object familiarity also affects spatial judgments of exocentric extents presented under conditions comparable to those of Carlson and Tassone's experiments. The markers of the extents were either familiar or unfamiliar objects. In Experiment 1, subjects reproduced the perceived extents of depth intervals by adjusting a comparison egocentric extent, and in Experiment 2, subjects also compared the relative depths of two equally long extents. In Experiment 3, the two equally long extents were presented in the subjects' frontoparallel plane, and the subjects reported which of these two extents appeared longer and farther away. The results of these experiments indicate that familiar size does not affect the perceived depths or lengths of exocentric extents viewed under naturalistic conditions.     

A balancing act: Physical balance, through arousal, influences size perception

Previous research has demonstrated that manipulating vision influences balance. Here, we question whether manipulating balance can influence vision and how it may influence vision--specifically, the perception of width. In Experiment 1, participants estimated the width of beams while balanced and unbalanced. When unbalanced, participants judged the widths to be smaller. One possible explanation is that unbalanced participants did not view the stimulus as long as when balanced because they were focused on remaining balanced. In Experiment 2, we tested this notion by limiting viewing time. Experiment 2 replicated the findings of Experiment 1, but viewing time had no effect on width judgments. In Experiment 3, participants' level of arousal was manipulated, because the balancing task likely produced arousal. While jogging, participants judged the beams to be smaller. In Experiment 4, participants completed another arousing task (counting backward by sevens) that did not involve movement. Again, participants judged the beams to be smaller when aroused. Experiment 5A raised participants' level of arousal before estimating the board widths (to control for potential dual-task effects) and showed that heightened arousal still influenced perceived width of the boards. Collectively, heightened levels of arousal, caused by multiple manipulations (including balance), influenced perceived width.     

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。     

Spatial judgments of exocentric extents in an open-field situation: Familiar versus unfamiliar size

Carlson and Tassone (1971) found that an object of familiar size presented in an outdoor setting and viewed at an appreciable distance is judged to be more distant than an unfamiliar object. Three experiments examined whether object familiarity also affects spatial judgments of exocentric extents presented under conditions comparable to those of Carlson and Tassone’s experiments. The markers of the extents were either familiar or unfamiliar objects. In Experiment 1, subjects reproduced the perceived extents of depth intervals by adjusting a comparison egocentric extent, and in Experiment 2, subjects also compared the relative depths of two equally long extents. In Experiment 3, the two equally long extents were presented in the subjects’ frontoparallel plane, and the subjects reported which of these two extents appeared longer and farther away. The results of these experiments indicate that familiar size does not affect the perceived depths or lengths of exocentric extents viewed under naturalistic conditions.     

Color and context: An ERP study on intrinsic and extrinsic feature binding in episodic memory

Episodic memory for intrinsic item and extrinsic context information is postulated to rely on two distinct types of representation: object and episodic tokens. These provide the basis for familiarity and recollection, respectively. Electrophysiological indices of these processes (ERP old-new effects) were used together with behavioral data to test these assumptions. We manipulated an intrinsic object feature (color; Experiment 1) and a contextual feature (background; Experiments 1 and 2). In an inclusion task (Experiment 1), the study-test manipulation of color affected object recognition performance and modulated ERP old-new effects associated with both familiarity and recollection. In contrast, a contextual manipulation had no effect, although both intrinsic and extrinsic information was available in a direct feature (source memory) test. When made task relevant (exclusion task; Experiment 2), however, context affected the ERP recollection effect, while still leaving the ERP familiarity effect uninfluenced. We conclude that intrinsic features bound in object tokens are involuntarily processed during object recognition, thus influencing familiarity, whereas context features bound in episodic tokens are voluntarily accessed, exclusively influencing recollection. Figures depicting all the electrodes analyzed are available in an online supplement at www.psychonomic.org/archive.     

Computation of mean size is based on perceived size

The present study investigated whether computation of mean object size was based on perceived or physical size. The Ebbinghaus illusion was used to make the perceived size of a circle different from its physical size. Four Ebbinghaus configurations were presented either simultaneously (Experiment 1) or sequentially (Experiment 2) to each visual field, and participants were instructed to attend only to the central circles of each configuration. Participants’ judgments of mean central circle size were influenced by the Ebbinghaus illusion. In addition, the Ebbinghaus illusion influenced the coding of individual size rather than the averaging. These results suggest that perceived rather than physical size was used in computing the mean size.     

The effects of familiar size on judgments of size and distance: An interaction of viewing attitude with spatial cues

Two hypotheses about the effects of familiar size on judgments of size and distance, the cue-conflict hypothesis and the viewing-attitude hypothesis, were examined. In Experiment 1, observers estimated the size and distance of familiar targets with apparent or assumptive instructions under three different spatial cue conditions. In Experiment 2, observers performed tasks similar to those of Experiment 1 with no specific instructions. The main results were: (1) Assumptive instructions facilitate the effects of familiar size in both size and distance judgments, but reducing spatial cues does not, and (2) viewing attitude changes from the apparent to the assumptive when available spatial cues are reduced. Thus, it was concluded that the viewing-attitude hypothesis gives a better account of the effects of familiar size, but that the cue-conflict hypothesis cannot be abandoned, because the number of conflicting cues contributes to the formation of viewing attitude.     

Examination of apparent extent as an explanation of the Poggendorff effect

The explanation of apparent misalignment in the Poggendorff figure, based on underestimation of the intertransversal distance, was investigated in two experiments. In Experiment 1, subjects judged the intertransversal distance in the traditional Poggendorff figure and two of its variants. The size of the acute angle and the intertransversal distance were manipulated. Half of the subjects made the judgments with the method used by Wilson and Pressey (1976) and the other half made their judgments with the method used by Greist-Bousquet and Schiffman (1981). The results indicated that perceived intertransversal distance was greater with the former method. In Experiment 2, subjects adjusted the transversals to apparent collinearity in the same displays as were used in Experiment 1. The collinearity judgments were transformed to allow comparison with the results of Experiment 1. Comparison of the collinearity judgments with the distance judgments indicated that they did not follow similar trends. For each Poggendorff variant, proportional distance judgments increased as the size of the acute angle increased, and decreased as the intertransversal distance increased. Collinearity judgments did not vary as a function of intertransversal distance. As the size of the acute angle increased, collinearity judgments increased for two of the Poggendorff variants but decreased for the third. It was concluded that the findings did not support the explanation of apparent misalignment based on underestimation of the intertransversal distance.     

Dimensional and metric structures in multidimensional stimuli

The present experiments investigated two characteristics of subjects’ multidimensional representations: their dimensional organization and metric structure, for both analyzable and integral stimuli. In Experiment 1, subjects judged the dissimilarity between all pairs of stimuli differing in brightness and size (analyzable stimuli), while in Experiment 2, subjects made dissimilarity judgments for stimuli varying in width height, and area shape (integral stimuli). For the brightness size stimuli, the findings that (a) brightness judgments were independent of size (and vice versa) and (b) the best fitting scaling solution was one that depicted an orthogonal structure are strong evidence that subjects perceived brightness size as a dimensionally organized structure. In contrast, for the rectangle stimuli, neither width height nor area shape contributed additively to overall dissimilarity. The results of the metric fitting were more equivocal. For all stimulus sets, the Euclidean metric yielded scaling solutions with lower stress values than the city block metric. When bidimensional ratings were regressed on unidimensional ratings, the city block metric yielded a slightly higher correlation coefficient than the Euclidean metric for brightness size stimuli. The two rules of combination were equivalent for the width-height stimuli, but the Euclidean metric provided a better approximation for the area shape stimuli. The results were discussed in terms of how subjects integrate physical dimensions for the case of integral stimuli and the superiority of dimensional vs. metric structure as an indicator of stimulus analyzability.     

Rewarded remembering: dissociations between self-rated motivation and memory performance

People often claim that they perform better in memory performance tasks when they are more motivated. However, past research has shown minimal effects of motivation on memory performance when factors contributing to item-specific biases during encoding and retrieval are taken into account. The purpose of the present study was to examine the generality of this apparent dissociation by using more sensitive measures of experienced motivation and memory performance. Extrinsic motivation was manipulated through competition instructions, and subjective ratings of intrinsic and extrinsic motivation were obtained before and after study instructions. Participants studied a series of words, and memory performance was assessed by content recall (Experiment 1) and source recall (Experiment 2). Both experiments showed dissociation between subjective ratings of extrinsic motivation and actual memory performance, so that competition increased self-rated extrinsic motivation but had no effects on memory performance, including source recall. Inconsistent with most people's expectations, the findings suggest that extrinsic motivation has minimal effects on memory performance.     

Category size and judgments of variability: The effects of seeing the trees in the forest1

Abstract: Competing predictions about the effects of category size on judgments of category variability were examined in two studies involving the presentation of exemplars of two artificial social groups. In contrast to predictions of some exemplar-based models, Experiment 1 demonstrated that a numerically smaller group was perceived to be more variable than a larger group on the standard deviation measure of frequency distribution estimates. The result was interpreted to be an effect of differential information load. Experiment 2 revealed that variability judgments were influenced by prior expectations about the central tendencies as well as by practice in retrieving information about category exemplars. When frequency distribution estimates were made subsequent to abstract tasks, expectations about the numerical majority reduced perceived variability, while this influence was mitigated when memory measures preceded the frequency estimates.     

Dorsal and ventral processing under dual-task conditions

It is widely acknowledged that visual input is processed along two anatomically and functionally distinct pathways--a ventral pathway for conscious perception and a dorsal pathway for action control. The present study investigated whether the apparent direct and unmediated processing in the dorsal stream is subject to capacity limitations. Specifically, we tested whether a simple dorsal task of grasping an object is affected by the psychological refractory period (PRP), a well-known indication of capacity limitations. Subjects performed an auditory choice reaction task and then, following varying delays, had to judge an object's width (ventral task) or grasp an object across its width (dorsal task). Although these tasks were differentially affected by irrelevant variation of the objects' length, they were subject to comparable dual-task interference. These results show that despite important differences between ventral and dorsal information processing, both modes of processing are constrained by limited capacities.     

Selection of strategies for narrowing choice options: Antecedents and consequences

This study investigates the antecedents (task and decision maker characteristics) and consequences (set size and decision quality) of prescreening strategy selection. In Experiment 1 we investigated which strategy, inclusion or exclusion, is more natural for narrowing choices in tasks with a single correct answer; about 70% of the participants selected exclusion. Experiment 2 directly contrasted correct answer tasks with personal judgment tasks, using the same foils for the two tasks. Participants were more likely to use exclusion for items with a correct answer than for personal judgments. In Experiment 3, participants could choose different strategies for different items and rated the difficulty of each item. The greater the perceived difficulty of an item, the more likely participants were to choose an exclusion strategy. In all three experiments exclusion led to larger set sizes, across task type and experimental design. There were no differences in decision quality as a function of strategy selection after correcting for set size. Individual differences based on personality inventories were not found to be good predictors of strategy selection, but had moderate effects on set size for personal judgment tasks. Results are discussed in terms of a status quo bias for adding or deleting options from an initial reference frame.     

Memory for scenes: Refixations reflect retrieval

Most conceptions of episodic memory hold that reinstatement of encoding operations is essential for retrieval success, but the specific mechanisms of retrieval reinstatement are not well understood. In three experiments, we used saccadic eye movements as a window for examining reinstatement in scene recognition. In Experiment 1, participants viewed complex scenes, while number of study fixations was controlled by using a gaze-contingent paradigm. In Experiment 2, effects of stimulus saliency were minimized by directing participants' eye movements during study. At test, participants made remember/know judgments for each recognized stimulus scene. Both experiments showed that remember responses were associated with more consistent study-test fixations than false rejections (Experiments 1 and 2) and know responses (Experiment 2). In Experiment 3, we examined the causal role of gaze consistency on retrieval by manipulating participants' expectations during recognition. After studying name and scene pairs, each test scene was preceded by the same or different name as during study. Participants made more consistent eye movements following a matching, rather than mismatching, scene name. Taken together, these findings suggest that explicit recollection is a function of perceptual reconstruction and that event memory influences gaze control in this active reconstruction process.     

The effect of polar projection on the perception of euclidean structure from motion

The aim of the present study was to examine whether euclidean structure could be recovered from apparent motion sequences under polar projection. In Experiment 1, length judgments of two sides of a simulated triangle rotating in depth did not reveal effects of type of projection, polar or parallel, on the perception of euclidean structure. However, there was a significant correlation between simulated and produced slants. The results also indicated that absolute depth judgments could not be accounted for by a random mechanism suggested by Todd and Bressan (1990). Experiments 2 and 3, in which a continuous dot surface was substituted for the triangle, showed that polar projection information from a relatively large visual angle, 17.40°, as compared with a small visual angle, 4.35°, facilitated discrimination of depth. Produced height:width ratios were consistently related to simulated shape, although the depth dimension was underestimated. Finally, Experiment 4 showed significant correlations between simulated and produced height:width ratios that could be accounted for only by an analysis in whichX andY velocities were treated independently. As in previous experiments, the variation in the depth dimension was underestimated. It was concluded that the visual system utilizes the additional information that is available in polar projection when recovering structure from motion, but that for different reasons the perceived structure does not become euclidean. These reasons are discussed briefly.     

Spatial memories of virtual environments: How egocentric experience, intrinsic structure, and extrinsic structure interact

Previous research has uncovered three primary cues that influence spatial memory organization:egocentric experience, intrinsic structure (object defined), and extrinsic structure (environment defined). In the present experiments, we assessed the relative importance of these cues when all three were available during learning. Participants learned layouts from two perspectives in immersive virtual reality. In Experiment 1, axes defined by intrinsic and extrinsic structures were in conflict, and learning occurred from two perspectives, each aligned with either the intrinsic or the extrinsic structure. Spatial memories were organized around a reference direction selected from the first perspective, regardless of its alignment with intrinsic or extrinsic structures. In Experiment 2, axes defined by intrinsic and extrinsic structures were congruent, and spatial memories were organized around reference axes defined by those congruent structures, rather than by the initially experienced view. The findings are discussed in the context of spatial memory theory as it relates to real and virtual environments.     

Motion and position shifts induced by the double-drift stimulus are unaffected by attentional load

The double-drift stimulus produces a strong shift in apparent motion direction that generates large errors of perceived position. In this study, we tested the effect of attentional load on the perceptual estimates of motion direction and position for double-drift stimuli. In each trial, four objects appeared, one in each quadrant of a large screen, and they moved upward or downward on an angled trajectory. The target object whose direction or position was to be judged was either cued with a small arrow prior to object motion (low attentional load condition) or cued after the objects stopped moving and disappeared (high attentional load condition). In Experiment 1, these objects appeared 10° from the central fixation, and participants reported the perceived direction of the target’s trajectory after the stimulus disappeared by adjusting the direction of an arrow at the center of the response screen. In Experiment 2, the four double-drift objects could appear between 6 ° and 14° from the central fixation, and participants reported the location of the target object after its disappearance by moving the position of a small circle on the response screen. The errors in direction and position judgments showed little effect of the attentional manipulation—similar errors were seen in both experiments whether or not the participant knew which double-drift object would be tested. This suggests that orienting endogenous attention (i.e., by only attending to one object in the precued trials) does not interact with the strength of the motion or position shifts for the double-drift stimulus.     

Eyeheight-scaled information about affordances: a study of sitting and stair climbing

Previous work has shown that both the perceived and actual critical (maximum) heights of surfaces that afford "sitting on " and "climbing on" can be expressed as constant proportions of each actor's leg length. The current study provides evidence that these judgments of critical action boundaries are based on an existing source of size and distance information that is already scaled with reference to the actor's eyeheight. In Experiment 1 changes in judgments of "perceived eyeheight" (an index of the intrinsic scalar) as a function of viewing distance were shown to be highly correlated with changes in the maximum height that was perceived to afford sitting on or climbing on. In Experiments 2 and 3 observers wore 10-cm blocks and made judgments about whether the heights of various surfaces afforded sitting or climbing. The use of eyeheight-scaled information as the basis for their estimates predicted the obtained pattern of errors in these judgments. With a modicum of experience wearing the blocks, however, observers were able to retune accurately their critical action boundary to a degree that would not have been predicted from their consistent overestimation of the height of the block on which they were standing. These results have implications for understanding how observers obtain information about their specific action boundary.