Contributions of invariants, heuristics, and exemplars to the visual perception of relative mass

Some potential contributions of invariants, heuristics, and exemplars to the perception of dynamic properties in the colliding balls task were explored. On each trial, an observer is asked to determine the heavier of 2 colliding balls. The invariant approach assumes that people can learn to detect complex visual patterns that reliably specify which ball is heavier. The heuristic approach assumes that observers only have access to simple motion cues. The exemplar-based approach assumes that people store particular exemplars of collisions in memory, which are later retrieved to perform the task. Mathematical models of these theories are contrasted in 2 experiments. Observers may use more than 1 strategy to determine relative mass. Although observers can learn to detect and use invariants, they may rely on either heuristics before the invariant has been learned or exemplars when memory demands and similarity relations allow.     

Individual differences and the use of nonspecifying variables in learning to perceive distance and size: comments on McConnell, Muchisky, and Bingham (1998).

McConnell, Muchisky, and Bingham (1998) showed that observers are able to judge the distance and size of falling, rolling, and swinging balls and that performance improves after practice with feedback. They concluded that observers use information that specifies the spatial scales of the different event types--namely, event duration in combination with event-specific constants. The improvement was interpreted as the calibration of the event-specific constants. We argue that their analyses should have considered the use of optical variables that do not specify the to-be-perceived metrics and individual differences in variable use. Furthermore, we propose convergence on the more useful variables as an alternative explanation for the observed improvement. The viability of these arguments is demonstrated with an experiment in which participants are trained with feedback to judge the distance and size of freely falling balls.     

Individual differences and the use of nonspecifying variables in learning to perceive distance and size: Comments on McConnell, Muchisky, and Bingham (1998)

McConnell, Muchisky, and Bingham (1998) showed that observers are able to judge the distance and size of falling, rolling, and swinging balls and that performance improves after practice with feedback. They concluded that observers use information that specifies the spatial scales of the different event types—namely, event duration in combination with event-specific constants. The improvement was interpreted as the calibration of the event-specific constants. We argue that their analyses should have considered the use of optical variables that do not specify the to-be-perceived metrics and individual differences in variable use. Furthermore, we propose convergence on the more useful variables as an alternative explanation for the observed improvement. The viability of these arguments is demonstrated with an experiment in which participants are trained with feedback to judge the distance and size of freely falling balls.     

Learning to visually perceive the relative mass of colliding balls in globally and locally constrained task ecologies

Novice observers differ from each other in the kinematic variables they use for the perception of kinetic properties, but they converge on more useful variables after practice with feedback. The colliding-balls paradigm was used to investigate how the convergence depends on the relations between the candidate variables and the to-be-perceived property, relative mass. Experiment 1 showed that observers do not change in the variables they use if the variables with which they start allow accurate performance. Experiment 2 showed that, at least for some observers, convergence can be facilitated by reducing the correlations between commonly used nonspecifying variables and relative mass but not by keeping those variables constant. Experiments 3a and 3b further demonstrated that observers learn not to rely on a particular nonspecifying variable if the correlation between that variable and relative mass is reduced.     

The effect of feedback training on distance estimation in virtual environments

It is often noted that distances are significantly underestimated in computer‐simulated (virtual) environments. Two experiments examine observers' ability to use error corrective feedback to improve the accuracy of judgments of egocentric and exocentric distances. In Experiment 1, observers viewed objects in an immersive virtual environment and estimated their distance through a blindfolded walking task. Different groups received feedback on either egocentric, exocentric or none of these judgments. Receiving feedback improved observers' ability to estimate only those distances for which feedback was provided. These effects persisted for at least 1 week. In Experiment 2, observers estimated egocentric distance by means of both a direct and indirect walking task. Receiving feedback on the direct walking task predominantly improved direct estimates and not indirect estimates. These findings suggest that although feedback training offers a relatively straightforward and immediate way of overcoming problems of distance estimation, its effects are specific to both the type of judgment and the type of response. Copyright © 2005 John Wiley & Sons, Ltd.     

Heading judgments in minimal environments: the value of a heuristic when invariants are rare

Observers made systematic heading judgments in two experiments simulating their translation through an environment with only two trees. When those trees converged or decelerated apart, observers tended to follow the invariant information and make heading judgments outside the near member of the pair. When those trees accelerated apart, however, observers tended to follow the heuristic information and make judgments outside the far member, although this result was tempered by the angular separation between the trees and their relative acceleration. The simultaneous existence and use of invariants and heuristics are discussed in terms of different metatheoretical approaches to perception.     

Sex and age modulate the visual perception of distance

An experiment was conducted to evaluate the ability of 28 younger and older adults to visually bisect distances in depth both indoors and outdoors; half of the observers were male and half were female. Observers viewed 15-m and 30-m distance extents in four different environmental settings (two outdoor grassy fields and an indoor hallway and atrium) and were required to adjust the position of a marker to place it at the midpoint of each stimulus distance interval. Overall, the observers’ judgments were more accurate indoors than outdoors. In outdoor environments, many individual observers exhibited perceptual compression of farther distances (e.g., these observers placed the marker closer than the actual physical midpoints of the stimulus distance intervals). There were significant modulatory effects of both age and sex upon the accuracy and precision of the observers’ judgments. The judgments of the male observers were more accurate than those of the female observers and they were less influenced by environmental context. In addition, the accuracies of the younger observers’ judgments were less influenced by context than those of the older observers. With regard to the precision of the observers’ judgments, the older females exhibited much more variability across repeated judgments than the other groups of observers (younger males, younger females, and older males). The results of our study demonstrate that age and sex are important variables that significantly affect the visual perception of distance.     

Vertical position as a cue to pictorial depth: Height in the picture plane versus distance to the horizon

Two often cited but frequently confused pictorial cues to perceived depth are height in the picture plane (HPP) and distance to the horizon (DH). We report two psychophysical experiments that disentangled their influence on perception of relative depth in pictures of the interior of a schematic room. Experiment 1 showed that when HPP and DH varied independently with both a ceiling and a floor plane visible in the picture, DH alone determined judgments of relative depth; HPP was irrelevant. Experiment 2 studied relative depth perception in single-plane displays (floor only or ceiling only) in which the horizon either was not visible or was always at the midpoint of the target object. When the target object was viewed against either a floor or a ceiling plane, some observers used DH, but others (erroneously) used HPP. In general, when DH is defined and unambiguous, observers use it to determine the relative distance to objects, but when DH is undefined and/or ambiguous, at least some observers use HPP.     

Lateral interception I: operative optical variables, attunement, and calibration

J. J. Gibson (1966, 1979) suggested that improvement in perception and action can be attributed in part to changes in which variable is attended to. Such reattunement has been demonstrated with observers making judgments in response to simulations. The present study sought attunement changes in the perception of real events and in visually guided action. In 3 experiments, adults judged the passing distance of or attempted to catch balls. Discrete measures and the predictions of a modified required velocity model (e.g., R. J. Bootsma, V. Fayt, F. T. J. M. Zaal, & M. Laurent, 1997) were used to reveal which variables were exploited. Participants differed from each other and, to some extent, changed in the optical variables used, in catching as well as judging. Nevertheless, the changes were much smaller than in previous simulation-judgment studies; calibration was also found to underlie the improvements in performance.     

The indispensability of precollision kinematics in the visual perception of relative mass

The visible kinematic pattern that occurs when objects collide contains information about the relative mass of the objects. Recently, Gilden and Proffitt (1989) have claimed that perceivers are limited to the use of simultaneous elemental cues and that therefore mass discrimination judgments are independent of whether the precollision epoch is visible or not. The present paper argues that their experimental results are irrelevant because crucial parameters were held constant, and that false conclusions were drawn because their data were not treated for what they are: threshold measurements obtained with the method of constant stimuli. Three experiments are reported, showingthat a high level of performance is attainable only when the whole event is visible, and thus that the effective information is extended over time. In addition, modified PROBIT analysis was used to determine what information observers use when the precollision epoch is occluded. Analytically complex invariants, based on vector components in the abstract collision-axis system, proved to have the best fit to the data. Thus the elementaristic premises in Gilden and Proffitt’s cue-heuristic model for relative mass perception are defeated.     

The proximity structure of achromatic surface colors and the impossibility of asymmetric lightness matching

In asymmetric lightness matching tasks, observers sometimes report that they cannot achieve satisfactory matches between achromatic surfaces under different neutral illuminants. The surfaces appear different, yet no further adjustment of either surface improves the match. There are evident difficulties in interpreting data from a task that the observer cannot always do, and these difficulties likely affect the interpretation of a large number of previous studies. We investigated, as an alternative to asymmetric matching, the direct use of proximity judgments in the study of surface lightness perception. We asked observers to rate the perceived dissimilarity of pairs of achromatic surfaces that were placed in identical scenes and viewed under different neutral illuminants. We develop a parametric model that accurately predicts perceived dissimilarity in terms of physical light intensities and surface albedos. The parameters of this model are readily interpretable. In particular, the ratio of the influence of changes in illuminant intensity and changes in surface albedo is a measure of the extent to which the observer discounts the illuminant. Asymmetric lightness matching can be interpreted as an unachievable limiting case of proximity judgment.     

The Dynamic Relationship Between Accuracy and Bias in Social Perception Research

How do perceivers make accurate social judgments? A substantial amount of evidence suggests that perceivers' judgments are often quite accurate even when they do not have direct access to the truth, in part because they make judgments through biased processes. In the present article, we examine the dynamic relationship between bias and accuracy in social perception research. We outline how bias and accuracy are theoretically and empirically distinct processes and describe the importance (and difficulty) of defining and measuring both truth variables and bias variables in order to make empirical conclusions in accuracy research. Additionally, we examine how both bias variables (e.g., stereotypes, perceivers' own beliefs) and truth variables exert an influence on how perceivers make social judgments, as well as the extent to which judgments are accurate. Lastly, we provide steps that researchers can take in order to examine the relationship between bias and accuracy in their own research.     

Base on balls for the Chapman strategy: Reassessing Brouwer, Brenner, and Smeets (2002)

A true understanding of skilled behavior includes the identification of the information that underlies the perception?Caction cycle at work. Often, observers?? sensitivity to perceptual variables is established in laboratory-situated simulation-based psychophysical experiments. The observers?? sensitivity thus determined is then used to draw conclusions that will generalize the findings to natural behavior. Focusing on the example of running to catch fly balls, the present contribution takes the study of Brouwer, Brenner, and Smeets (Perception & Psychophysics 64:1160?C1168, 2002) to illustrate how common assumptions in the steps from psychophysical experiments to natural behavior can result in ungrounded conclusions. These authors built an argument to reject the use of the Chapman strategy of zeroing out optical acceleration. For this argument, they determined the sensitivity of the visual system to acceleration, assuming that acceleration is detected as a velocity ratio. Next, they showed that catchers started running earlier than could be expected on the basis of sensitivity thresholds for this velocity ratio, concluding that running initiation could not have been based on optical acceleration. In the present study, we argue that important assumptions in the Brouwer et al. (Perception & Psychophysics 64:1160?C1168, 2002) line of argument are incorrect. First, we show how the assumption of parabolic ball flight trajectories, although convenient, biased Brouwer et al.??s (Perception & Psychophysics 64:1160?C1168, 2002) conclusion. Next, we present an experiment revealing that observers do not base their judgments of acceleration on the velocity ratio. Thus, we demonstrate that Brouwer et al.??s (Perception & Psychophysics 64:1160?C1168, 2002) argument that optical acceleration cannot serve as the information for running to catch fly balls does not hold.     

Commentary on Jacobs and Michaels (2001): Calibration and perceptual learning in event perception

Jacobs and Michaels (2001) have argued that increased precision in judgments of the viewing distance to a perceived event should be attributed in part to perceptual learning. They found that observers used feedback to attune to the appropriate information variables gradually. McConnell, Muchisky, and Bingham (1998) had found that observers used feedback to calibrate event-specific scaling coefficients, that the calibration of one type of event generalized to other types, and that calibration occurred suddenly. We argue that Jacobs and Michaels must be partially correct and that, in our experiments, both calibration and perceptual attunement were required for accurate and precise judgments.     

Commentary on Jacobs and Michaels (2001): calibration and perceptual learning in event perception.

Jacobs and Michaels (2001) have argued that increased precision in judgments of the viewing distance to a perceived event should be attributed in part to perceptual learning. They found that observers used feedback to attune to the appropriate information variables gradually. McConnell, Muchisky, and Bingham (1998) had found that observers used feedback to calibrate event-specific scaling coefficients, that the calibration of one type of event generalized to other types, and that calibration occurred suddenly. We argue that Jacobs and Michaels must be partially correct and that, in our experiments, both calibration and perceptual attunement were required for accurate and precise judgments.     

Continuous Response Monitoring of Relative Time-to-Contact Judgments: Does Effective Information Change During an Approach Event?

In many previous studies of time-to-contact (TTC) judgments of approaching objects, a response was measured after observers viewed the entire event and was used to infer the informational basis for the judgment. Such measures primarily reflect the information used at the end of the approach event and may not reveal whether observers used different information at different times during the event. Evidence indicates that observers use multiple information sources and that the effectiveness of information varies with distance. We introduce a method in which observers continuously report which of 2 approaching objects would reach them first, throughout the approach. We identified the occurrence and time of response reversals. Most observers changed their relative TTC judgments during the event. The pattern of responses indicated that observers did not use tau early during the approach when objects were far and did not use optical size later when the objects were closer. Most observers relied on either optical size or optical expansion rate early during the approach and expansion rate later during the event, although there were individual differences. A single relative TTC judgment measured after observers view an approach event may not reflect judgments or their informational basis throughout the entire event.     

People use the memory for past-test heuristic as an explicit cue for judgments of learning

When people estimate their memory for to-be-learned material over multiple study–test trials, they tend to base their judgments of learning (JOLs) on their test performance for those materials on the previous trial. Their use of this information—known as the memory for past-test (MPT) heuristic—is believed to be responsible for improvements in the relative accuracy (resolution) of people’s JOLs across learning trials. Although participants seem to use past-test information as a major basis for their JOLs, little is known about how learners translate this information into a judgment of learning. Toward this end, in two experiments, we examined whether participants factored past-test performance into their JOLs in either an explicit, theory-based way or an implicit way. To do so, we had one group of participants (learners) study paired associates, make JOLs, and take a test on two study–test trials. Other participants (observers) viewed learners’ protocols and made JOLs for the learners. Presumably, observers could only use theory-based information to make JOLs for the learners, which allowed us to estimate the contribution of explicit and implicit information to learners’ JOLs. Our analyses suggest that all participants factored simple past-test performance into their JOLs in an explicit, theory-based way but that this information made limited contributions to improvements in relative accuracy across trials. In contrast, learners also used other privileged, implicit information about their learning to inform their judgments (that observers had no access to) that allowed them to achieve further improvements in relative accuracy across trials.     

The impact of visual exploration of judgments of whether a gap is crossable

When observers look down into a gap in the ground plane, their judgments of the widest gap they can step across (gapmax) decrease as gap depth increases (Y. Jiang & L. S. Mark, 1994). This study investigated the possibility that Jiang and Mark's viewing conditions did not afford observers a sufficient opportunity to perform exploratory movements needed to detect information about gap width. Experiment 1 showed that the gap depth by gaze interaction disappeared only when restrictions were not imposed on observers' exploratory activities (eye, head, and body movements). Experiment 2 showed that observers tended to see the vertical surface as slanted away from them, which made the bottom of the surface appear farther away from them than the top. Only when observers were able to view the gap binocularly under conditions that did not restrict exploratory activity did their slant perception improve and their gapmax judgments no longer covary with gap depth. The data indicate that the exploratory movements of prospective actors are essential for the pickup of information about their action capabilities.     

Using direct and indirect measures to study perception without awareness

Many studies directed at demonstrating perception without awareness have relied on the dissociation paradigm. Although the logic underlying this paradigm is relatively straightforward, definitive results have been elusive in the absence of any general consensus as to what constitutes an adequate measure of awareness. We propose an alternative approach that involves comparisons of the relative sensitivity of comparable direct and indirect indexes of perception. The only assumption required by the proposed approach is that the sensitivity of direct discriminations to relevant conscious information is greater than or equal to the sensitivity of comparable indirect discriminations. The proposed approach is illustrated through an evaluation of Avant and Thieman’s (1985) recent claim that an indirect measure of perception based on judgments of apparent visual duration provides a more sensitive indicator of perception than does a direct measure based on forced-choice recognition. Contrary to this claim, when direct and indirect indexes are measured under comparable conditions, an indirect measure based on judgments of perceived duration provides a less sensitive index of perceptual processing than do comparable direct measures. The proposed approach provides a general conceptual/methodological framework for using the dissociation paradigm in studies directed at establishing unconscious processes.     

The perception of 3-dimensional affine structure from minimal apparent motion sequences

The research described in the present article was designed to identify the minimal conditions for the visual perception of 3-dimensional structure from motion by comparing the theoretical limitations of ideal observers with the perceptual performance of actual human subjects on a variety of psychophysical tasks. The research began with a mathematical analysis, which showed that 2-frame apparent motion sequences are theoretically sufficient to distinguish between rigid and nonrigid motion and to identify structural properties of an object that remain invariant under affine transformations, but that 3 or more distinct frames are theoretically necessary to adequately specify properties of euclidean structure such as the relative 3-dimensional lengths or angles between nonparallel line segments. A series of four experiments was then performed to verify the psychological validity of this analysis. The results demonstrated that the determination of structure from motion in actual human observers may be restricted to the use of first order temporal relations, which are available within 2-frame apparent motion sequences. That is to say, the accuracy of observers' judgments did not improve in any of these experiments as the number of distinct frames in an apparent motion sequence was increased from 2 to 8, and performance on tasks involving affine structure was of an order of magnitude greater than performance on similar tasks involving euclidean structure.