Information used in detecting upcoming collision

In four experiments we examined the nature of the information used in judging whether events would or would not give rise to a collision in the near future. Observers were tested in situations depicting approaches between two objects (lateral approaches) and approaches between an object and the point of observation (head-on approaches), with objects moving according to constant deceleration or sinusoidal deceleration patterns. Judgments were found to be based, to a large extent, on the (in)sufficiency of current deceleration to avoid upcoming collision, as specified optically by tau-dot (tau). However, the information specified by tau (tau), that is the current (first-order) time remaining until contact, was also found to play a significant role. We deduce that judgment of upcoming collision is based on the detection of tau and its evolution over time, suggesting that observers are sensitive to delta(tau) rather than to tau itself.     

Optical Specification of Time-to-Contact for a Spectator

In the article, we provide an account of the informational basis underlying judgments of time-to-contract (TTC) under the conditions examined in Kim, Effken, and Carello (1998), in which observers watched collisions between 2 objects from various vantage points, over varying collision paths, and with additional observer movement. First, we examine the informational candidates proposed by Bootsma and his colleagues (e.g., Bootsma & Oudejans, 1993) and by Tresilian (1990). Simulation results showed that these models do not accurately describe TTc for such varying conditions. We present an alternative model, emphasizing the advantages of body scaling. Our model applied this scaling to the vertical gap between edges of the opposing surfaces of each object. Because all model terms are expressed in eyeheight units, distortions that occurred in the other models due to polar injection are eliminated. The proposed model provided veridical estimates of TTC for straight-line collision cases over a variety of viewing angles and with the addition of observer movement, but not for collisions along circular paths, in which the model only approximated TTC values.     

Braking reaching movements: a test of the constant tau-dot strategy under different viewing conditions

Following F. Zaal and R. J. Bootsma (1995), the authors studied whether the decelerative phase of a reaching movement could be modeled as a constant tau-dot strategy resulting in a soft collision with the object. Specifically, they investigated whether that strategy is sustained over different viewing conditions. Participants (N = 11) were required to reach for 15- and 50-mm objects at 2 different distances under 3 conditions in which visual availability of the immediate environment and of the reaching hand were varied. Tau-dot estimates and goodness-of-fit were highly similar across the 3 conditions. Only within-participant variability of tau-dot estimates was increased when environmental cues were removed. That finding suggests that the motor system uses a tau-dot strategy involving the intermodal (i.e., visual, proprioceptive, or both) specification of information to regulate the decelerative phase of reaching under restricted viewing conditions. The authors provide recommendations for improving the derivation of tau;(x) estimates and stress the need for further research on how time-to-contact information is used in the regulation of the dynamics of actions such as reaching.     

Age-related differences in collision detection during deceleration

Observers were presented with displays simulating a 3-D environment with obstacles in the path of motion. During the trial, observer motion decelerated at a constant rate and was followed by a blackout prior to the end of the display. On some trials the rate of deceleration resulted in stopping before the collision, whereas on other trials the rate of deceleration resulted in a collision with the obstacles. The observer's task was to detect which trials simulated an impending collision. Proportion of collision judgments was greater for older as compared with younger observers when a collision was not simulated. Older observers showed less sensitivity to detect collisions than younger observers did, particularly at high speeds. The age-dependent results are discussed in terms of analyses based on tau and constant deceleration. The results suggest that increased accident rates for older drivers may be due to an inability to detect collisions at high speeds.     

Aging and the detection of observer and moving object collisions

The authors examined age-related differences in the detection of collision events. Older and younger observers were presented with displays simulating approaching objects that would either collide or pass by the observer. In 4 experiments, the authors found that older observers, as compared with younger observers, had less sensitivity in detecting collisions with an increase in speed, at shorter display durations, and with longer time-to-contact conditions. Older observers also had greater difficulty when the scenario simulated observer motion, suggesting that older observers have difficulty discriminating object motion expansion from background expansion from observer motion. The results of these studies support the expansion sensitivity hypothesis-that age-related decrements in detecting collision events involving moving objects are the result of a decreased sensitivity to recover expansion information.     

Launching the effect: Representations of causal movements are influenced by what they lead to

We investigated whether the representation of an observed causal movement is influenced by its observed effect. Subjects watched displays showing collisions between two objects. In this 'launching event' (Michotte, 1946/1963), one of the two objects (Object A) started to move and set a second, initially stationary, object (Object B) into motion, which gave a strong impression of apparent causality. The apparent effectiveness of A's movement was manipulated by varying the velocities of A and B. When the velocity of B was higher than that of A, the effectiveness of the collision was high; when it was smaller it was low. Then, subjects were asked to reproduce the velocity of the causal movement. Reproduced velocity followed the velocity of both Object A and Object B, which supports the hypothesis that the effect of a movement is integrated with its apparent cause. However, when apparent causality was reduced by changing the direction of motion of B or by covering the point of collision, the influence of the effect on the representation of the cause persisted, suggesting that retroactive interference may account for the findings. The interference effect could not be reduced to temporal recency or spatial integration and was not obtained in the reverse temporal order (proactive interference). Rather, the two successive movements were blended in memory.     

Looking ahead: Attending to anticipatory locations increases perception of control

When people manipulate a moving object, such as writing with a pen or driving a car, they experience their actions as intimately related to the object’s motion, that is they perceive control. Here, we tested the hypothesis that observers would feel more control over a moving object if an unrelated task drew attention to a location to which the object subsequently moved. Participants steered an object within a narrow path and discriminated the color of a flash that appeared briefly close to the object. Across two experiments, participants provided higher ratings of perceived control when an object moved over a flash’s location than when an object moved away from a flash’s location. This result suggests that we use the location of spatial attention to determine the perception of control. If an object goes where we are attending, we feel like we made it go there.     

Detection of collision events on curved trajectories: optical information from invariant rate-of-bearing change

Previous research (Andersen & Kim, 2001) has shown that a linear trajectory collision event (i.e., a collision between a moving object and an observer) is specified by objects that expand and maintain a constant bearing (the object location remains constant in the visual field). In the present study, we examined the optical information for detecting a collision event when the trajectory was of constant curvature. Under these conditions, a collision event is specified by expansion of an object and a constant rate-of-bearing change. Three experiments were conducted in which trajectory curvature and display duration were varied while time to contact, speed, and initial image position of the collision objects were maintained. The results indicated that collision detection performance decreased with an increase in trajectory curvature and decreased with a decrease in display duration, especially for highly curved trajectories. In Experiment 3, we found that the presentation of a constant rate-of-bearing change in noncollision stimuli resulted in an increase in the false alarm rate. These results demonstrate that observers can detect collision events on curved trajectories and that observers utilize bearing change information.     

Cyclists’ intentions to yield for automated cars at intersections when they have right of way: Results of an experiment using high-quality video animations

What will cyclists do in future conflict situations with automated cars at intersections when the cyclist has the right of way? In order to explore this, short high-quality animation videos of conflicts between a car and a cyclist at five different intersections were developed. These videos were ‘shot’ from the perspective of the cyclist and ended when a collision was imminent should the car or the bicyclist not slow down. After each video participants indicated whether they would slow down or continue cycling, how confident they were about this decision, what they thought the car would do, and how confident they were about what the car would do. The appearance of the approaching car was varied as within-subjects variable with 3 levels (Car type): automated car, automated car displaying its intentions to the cyclists, and traditional car. In all situations the cyclist had right of way. Of each conflict, three versions were made that differed in the moment that the video ended by cutting off fractions from the longest version, thus creating videos with an early, mid, and late moment for the cyclist to decide to continue cycling or to slow down (Decision moment). Before the video experiment started the participants watched an introductory video about automated vehicles that served as prime. This video was either positive, negative, or neutral about automated vehicles (Prime type). Both Decision moment and Prime type were between subject variables. After the experiment participants completed a short questionnaire about trust in technology and trust in automated vehicles. 1009 participants divided in nine groups (one per Decision moment and Prime) completed the online experiment in which they watched fifteen videos (5 conflicts × 3 car types). The results show that participants more often yielded when the approaching car was an automated car than when it was a traditional car. However, when the approaching car was an automated car that could communicate its intentions, they yielded less often than for a traditional car. The earlier the Decision moment, the more often participants yielded but this increase in yielding did not differ between the three car types. Participants yielded more often for automated cars (both types) after they watched the negative prime video before the experiment than when they watched the positive video. The less participants trusted technology, and the capabilities of automated vehicles in particular, the more they were inclined to slow down in the conflict situations with automated cars. The association between trust and yielding was stronger for trust in the capabilities of automated vehicles than for trust in technology in general.     

Perceptual information and attentional constraints in visual search of collision events

This study examined the detection of collision events when multiple moving objects were present in the scene. Observers were presented with displays simulating a 3-D environment with multiple moving objects. The authors examined the ability of observers to detect collisions using a signal-detection paradigm and a visual search paradigm. The results indicated that, overall, observers were quite accurate at detecting collisions. Observers used both expansion information and static position to detect collisions, with expansion information being the more important source. Singleton search conditions were not processed in parallel, and conjunction search conditions had poorer performance than singleton search conditions. In addition, reaction times were greater for target-present trials as compared with target-absent trials. The results are interpreted in terms of 4 visual search hypotheses for collision detection when multiple moving objects are present.     

Body Posture and the Feeling of Social Closeness: An Exploratory Study in a Naturalistic Setting

Previous research has shown that body postures and body movements influence people’s attitudes, preferences and feelings. In the present study, we explored the influence of body posture on the feeling of closeness towards others and how this effect may interact with contextual variables. Study 1 was conducted in a naturalistic setting in which 127 participants observed a series of live dance sequences either standing up or remaining seated. After each sequence, participants reported the feelings elicited by the dance performance on a questionnaire. Visibility of performers’ facial expressions and background tempo were used as contextual variables. Results showed that participants who watched the performance standing up felt significantly closer to the dancers than participants who remained seated. Study 2 was carried out in a laboratory setting to explore the relationship between body posture, tempo and heart rate. Results showed a significant increase in heart rate when standing compared to when sitting and no effect of tempo. The present research demonstrates a link between body posture and social connection providing evidence that standing up strengthens the feeling of closeness to others, and showing that posture not only has an impact on self-related feelings (e.g. fear, anger, sadness) as previous research has shown, but also has an impact on feelings towards others at the base of all human social relations. The present research also suggests that heart rate may be a mediator of the effect of posture on the feeling of closeness.     

Appraising Loftus and Palmer (1974) post-event information versus concurrent commentary in the context of sport

Two experiments were conducted to examine framing effects in sport. In Experiment 1, a conceptual replication [Loftus, E. F., & Palmer, J. C. (1974). Reconstruction of automobile destruction: An example of the interaction between language and memory. Journal of Verbal Learning and Verbal Behavior, 13(5), 585–589], participants watched a hockey collision, with the hit described later in a written format as a “contact”, “bump”, or “smash”. This manipulation resulted in no differences in participants’ report of how fast the players were skating, their intentions, and the outcome of the hit. In Experiment 2, participants watched the same video clip with ongoing commentary. Those who heard the announcer describing the event as “contact” estimated a higher skating speed than participants who were exposed to the “smash” commentary. Participants who were exposed to the “bump” commentary rated the repercussions of the collision as less severe than did those exposed to the other commentaries. These findings show that the perception of magnitude hierarchy may be domain specific and suggest future avenues for exploring framing effects when one is exposed to visual stimuli.     

Size-arrival effects: The potential roles of conflicts between monocular and binocular time-to-contact information, and of computer aliasing

With computer simulations of self-motion, participants approached a floating object and tried to “jump” over it without collision. Participants “jumped” significantly later over small objects than they did over larger objects. This occurred when the displays were viewed monocularly or binocularly, a finding that suggests that such size-arrival effects (DeLucia & Warren, 1994) were not due to a conflict between monocular and binocular cues to time-to-contact (TTC) information (Tresilian, 1994,1995). Moreover, the results further suggest that size-arrival effects are not due to irregularities in TTC information that can occur from computer abasing and that the latter does not always affect TTC estimation; visual information used in such judgments does not seem to be extracted on a frame-by-frame basis.     

Size-arrival effects: the potential roles of conflicts between monocular and binocular time-to-contact information, and of computer aliasing.

With computer simulations of self-motion, participants approached a floating object and tried to "jump" over it without collision. Participants "jumped" significantly later over small objects than they did over larger objects. This occurred when the displays were viewed monocularly or binocularly, a finding that suggests that such size-arrival effects (DeLucia & Warren, 1994) were not due to a conflict between monocular and binocular cues to time-to-contact (TTC) information (Tresilian, 1994, 1995). Moreover, the results further suggest that size-arrival effects are not due to irregularities in TTC information that can occur from computer aliasing and that the latter does not always affect TTC estimation; visual information used in such judgments does not seem to be extracted on a frame-by-frame basis.     

Calibration, information, and control strategies for braking to avoid a collision

This study explored visual control strategies for braking to avoid collision by manipulating information about speed of self-motion. Participants watched computer-generated displays and used a brake to stop at an object in the path of motion. Global optic flow rate and edge rate were manipulated by adjusting eye-height and ground-texture size. Stopping distance, initiation of braking, and the magnitude of brake adjustments were influenced by both optical variables, but global optic flow rate had a stronger effect. A new model is introduced according to which braking is controlled by keeping the perceived ideal deceleration, based in part on global optic flow rate, within a "safe" region between 0 and the maximum deceleration of the brake.     

Visual awareness of objects and their colour

At any given moment, our awareness of what we 'see' before us seems to be rather limited. If, for instance, a display containing multiple objects is shown (red or green disks), when one object is suddenly covered at random, observers are often little better than chance in reporting about its colour (Wolfe, Reinecke, & Brawn, Visual Cognition, 14, 749-780, 2006). We tested whether, when object attributes (such as colour) are unknown, observers still retain any knowledge of the presence of that object at a display location. Experiments 1-3 involved a task requiring two-alternative (yes/no) responses about the presence or absence of a colour-defined object at a probed location. On this task, if participants knew about the presence of an object at a location, responses indicated that they also knew about its colour. A fourth experiment presented the same displays but required a three-alternative response. This task did result in a data pattern consistent with participants' knowing more about the locations of objects within a display than about their individual colours. However, this location advantage, while highly significant, was rather small in magnitude. Results are compared with those of Huang (Journal of Vision, 10(10, Art. 24), 1-17, 2010), who also reported an advantage for object locations, but under quite different task conditions.     

Salience drives overt selection of two equally relevant visual targets

In the present study, we investigated whether salience determines the sequence of selection when participants search for two equally relevant visual targets. To do this, attentional selection was tracked overtly as observers inspected two items of differing physical salience: one a highly salient color singleton, and the other a less salient shape singleton. Participants were instructed to make natural eye movements in order to determine whether two line segments contained within the two singletons were oriented in the same or in different directions. Because both singleton items were task-relevant, participants had no reason to inspect one item before the other. As expected, observers fixated both targets on the majority of trials. Critically, saccades to the color singleton preceded saccades to the less salient shape singleton on the majority of trials. This demonstrates that the order of attentional object selection is largely determined by stimulus salience when task relevance is equated.     

Perceptual latencies to discriminate surface orientation in stereopsis

The difference in sensitivity to stereoscopic surfaces oriented horizontally or vertically (the stereoscopic orientation anisotropy) can be redescribed as a difference in sensitivity to shear or compression transformations that relate the binocular images. The present experiment was designed to test this by dissociating the image transformation from the orientation of the surface. Surfaces were presented in isolation or in the presence of a surrounding frame that formed step and gradient discontinuities in the disparity field. Without discontinuities, observers required considerably more time to discriminate between surfaces differing in compression than between those differing in shear, irrespective of surface orientation. Disparity discontinuities facilitated the perception of the disparity gradients; minimum stimulus durations were reduced by over an order of magnitude when the reference frame was present. These results support the hypothesis that the disparity field is decomposed into different primitives during the recovery of depth and surface structure.     

Relational message interpretations of nonverbal matching behavior: an application of the social meaning model

The social meaning model asserts that some nonverbal behaviors have consensually recognized relational meanings within a given social community. According to this perspective, the interpretations made by encoders, decoders, and 3rd-party observers of the same nonverbal behavior should be congruent. The authors applied the model to the identification of relational message interpretations of nonverbal matching behavior. Confederates either matched or did not match the nonverbal behaviors of conversational participants while being watched by nonparticipant observers. All three nonconfederate participants provided interpretations of the confederates' relational messages. As the authors had expected, there were moderate correlations between the 3 perspectives, with observers usually providing less favorable assessments than the conversational participants. The authors also examined the influence of positive and negative stimulus behavior on relational message interpretations.     

Distorted subjective reports of stimulus onsets under dual-task conditions: Delayed conscious perception or estimation bias?

We investigated whether selecting a response for one task delays the conscious perception of another stimulus (delayed conscious perception hypothesis). In two experiments, participants watched a revolving clock hand while performing two tasks in close succession (i.e. a dual-task). Two stimuli were presented with varying stimulus onset asynchrony (SOA). After each trial, participants separately estimated the onsets of the two stimuli on the clock face. Across two experiments and four conditions, we manipulated response requirements and assessed their impact on perceived stimulus onsets. Results showed that (a) providing speeded responses to the stimuli did lead to greater SOA-dependent misperceptions of both stimulus onsets as compared to a solely perceptual condition, and (b) that response grouping reduced these misperceptions. Overall, the results provide equivocal evidence for the delayed conscious perception hypothesis. They rather suggest that participants’ estimates of the two stimulus onsets are biased by the interval between their responses.