The formation of reference systems in visual motion perception

Summary In visual perception complex movements are usually split up into components — e.g., in such a way that a moving reference system is applied, to which partial movements can be related. In the following experiment a perceptual vector analysis of this kind was investigated. It was shown that 1) a radial translatory movement (relative component) can be isolated perceptually from a rotatory movement (global component) and that 2) the precision of this decomposition of the complex movement is dependent on the strength at which the rotating reference system is anchored perceptually.The authors wish to thank M. Rauterberg for collecting the experimental data     

Frames of reference in unilateral neglect and visual perception: a computational perspective

Neurological patients with unilateral neglect fail to orient and respond to stimuli on one side, typically the left. A key research issue is whether neglect is exhibited with respect to the left side of the viewer or of objects. When deficits in attentional allocation depend not merely on an object's location with respect to the viewer but on the object's intrinsic extent, shape, or movement, researchers have inferred that attention must be operating in an object-based frame of reference. Simulations of a view-based connectionist model of spatial attention prove that this inference is not logically necessary: Object-based attentional effects can be obtained without object-based frames. The model thus explains away troublesome phenomena for view-based theories of object recognition.     

Change of a frame of reference with velocity in visual motion perception

The present study examined how a frame of reference was affected by velocity. This question was examined with respect to a system consisting of two points: one moved rectilinearly with constant velocity, and the other moved on a track in the shape of a cycloid (defined as the movement of two points—one on the hub and the other on the rim of a rolling wheel). The results indicated that (1) a frame of reference in which the centroid of the total picture was stationary was chosen mainly in a low-velocity range (0.1–0.7 deg/sec), (2) a frame of reference in which a picture point moved rectilinearly was chosen mainly in a medium-velocity range (0.8–40.0 deg/sec), and (3) an absolute coordinate system was chosen mainly in a high-velocity range (>40.0 deg/sec). The current evidence and other findings seem to be consistent with the idea that groups of neurons related to the three frames of reference are independent of one another, that the velocity ranges of the groups of neurons roughly overlapped each other, and that the most salient frame of reference is chosen (i.e., exclusion principle in choice of a frame of reference).     

Frames of reference in spatial span

In four experiments, a computerized Corsi-like paradigm was used to assess which of the many reference frames are used in visuospatial short-term memory. By varying the relative orientation (slanted +/–45° or in an upright position) of the head and the displays, we modulate the utility of the allocentric, egocentric (eye- and head-centred), and template-centred reference frames. The results of all experiments showed the crucial importance of the gravitational allocentric reference frames while using visuospatial short-term memory to retain a spatial sequence of elements. The results also provide some support for a mental rotation process involved in recognition following angular displacement of a multi-item display.     

Frames of reference in social cognition

How is mindreading affected by social context? It is often implicitly assumed that there is one single way to understand others, whatever the situation or the identity of the person. In contrast, I emphasize the duality of functions of mindreading depending on the context (social interaction and social observation), as well as the duality of social frames of reference (egocentric and allocentric). I argue in favour of a functional distinction between knowledge-oriented mindreading and interaction-oriented mindreading. They both aim at understanding other people's behaviour. But they do so using different strategies. However, to say that mindreading has two functions does not suffice to show that there are two kinds of mindreading. One and the same ability could accomplish different functions. Unfortunately, there has been almost no experimental data on a possible dissociation between two kinds of mindreading abilities. Nonetheless, I discuss a few results that point towards a dual ability.     

Frames of reference in spatial span

In four experiments, a computerized Corsi-like paradigm was used to assess which of the many reference frames are used in visuospatial short-term memory. By varying the relative orientation (slanted +/-45° or in an upright position) of the head and the displays, we modulate the utility of the allocentric, egocentric (eye- and head-centred), and template-centred reference frames. The results of all experiments showed the crucial importance of the gravitational allocentric reference frames while using visuospatial short-term memory to retain a spatial sequence of elements. The results also provide some support for a mental rotation process involved in recognition following angular displacement of a multi-item display.     

Frames of reference in spatial language acquisition

Languages differ in how they encode spatial frames of reference. It is unknown how children acquire the particular frame-of-reference terms in their language (e.g., left/right, north/south). The present paper uses a word-learning paradigm to investigate 4-year-old English-speaking children’s acquisition of such terms. In Part I, with five experiments, we contrasted children’s acquisition of novel word pairs meaning left-right and north-south to examine their initial hypotheses and the relative ease of learning the meanings of these terms. Children interpreted ambiguous spatial terms as having environment-based meanings akin to north and south, and they readily learned and generalized north-south meanings. These studies provide the first direct evidence that children invoke geocentric representations in spatial language acquisition. However, the studies leave unanswered how children ultimately acquire “left” and “right.” In Part II, with three more experiments, we investigated why children struggle to master body-based frame-of-reference words. Children successfully learned “left” and “right” when the novel words were systematically introduced on their own bodies and extended these words to novel (intrinsic and relative) uses; however, they had difficulty learning to talk about the left and right sides of a doll. This difficulty was paralleled in identifying the left and right sides of the doll in a non-linguistic memory task. In contrast, children had no difficulties learning to label the front and back sides of a doll. These studies begin to paint a detailed account of the acquisition of spatial terms in English, and provide insights into the origins of diverse spatial reference frames in the world’s languages.     

Frames of reference in mobile augmented reality displays

In 3 experiments, the authors investigated spatial updating in augmented reality environments. Participants learned locations of virtual objects on the physical floor. They were turned to appropriate facing directions while blindfolded before making pointing judgments (e.g., "Imagine you are facing X. Point to Y"). Experiments manipulated the angular difference between the learning heading and the imagined heading and between the actual heading and the imagined heading. The effect of actual-imagined on pointing latency was observed for naive users but not for users with brief training or instructions concerning the fact that objects can move with body movements. The results indicated that naive users used an environment-stabilized reference frame to access information arrays, but with experience and instruction the nature of the representation changed from an environment stabilized to a body stabilized reference frame.     

Frames of reference and cooperative social decision-making

Cooperative decision-making was studied as a function of the decision-makers' own, and the interdependent other party's gain or loss frame. As expected, results showed that (a) an own gain frame produced less cognitive activity than an own loss frame and (b) other's loss frame caused more cooperation than other's gain frame, but only in case of an own gain frame.     

Frames of reference for self-evaluation of ability in mathematics

Measures of eight frame-specific self-evaluations of ability in mathematics were used to predict general mathematics self-concept and self-efficacy. Participants were 900 Norwegian students in Grade 6 (n = 277), Grade 9 (n = 236), Grade 11 (n = 263), and adult students attending senior high school (n = 124). Four items measured frame-specific self-evaluation of achievement based on external frames of reference whereas four items measured frame-specific self-evaluation based on internal frames of reference. Regression analyses were used to test relations between the frame-specific self-evaluations and general mathematics self-concept and self-efficacy. The analyses indicated that self-evaluation based on comparison with other students in class (an external frame of reference) and on comparison of mathematics achievement with achievement in other school subjects (an internal frame of reference) were robust predictors of both mathematics self-concept and self-efficacy. The analyses also indicated that students are using multiple frames of reference when evaluating their mathematics ability. Implications of the result for the internal-external frame of reference model are discussed.     

Adaptation in motion perception: Alteration of induced motion

Prolonged exposure to a condition that causes induced motion was found to diminish this effect. The extent of a horizontal induced motion was measured by obtaining estimates of the direction of the apparent oblique path that resulted when a spot was visible on a horizontally moving pattern and was therefore in horizontal induced motion and, at the same time, moved vertically. Because the horizontal component of the perceived motion path represented the induced motion, the slope of the path measured the extent of the induced motion. After a 10-min exposure to induced motion, the apparent motion path was steeper; the mean change corresponded to a 15% smaller extent of the induced motion. Results were obtained that argue that this effect is not due to a diminished horizontal motion of the pattern but amounts to a smaller motion-inducing effect. The experiments were meant to support the view that the perceptual process that underlies induced motion is learned.     

Frames of reference in spatial memories acquired from language

Four experiments examined reference systems in spatial memories acquired from language. Participants read narratives that located 4 objects in canonical (front, back, left, right) or noncanonical (left front, right front, left back, right back) positions around them. Participants' focus of attention was first set on each of the 4 objects, and then they were asked to report the name of the object at the location indicated by a direction word or an iconic arrow. The results indicated that spatial memories were represented in terms of intrinsic (object-to-object) reference systems, which were selected using egocentric cues (e.g., alignment with body axes). Results also indicated that linguistic direction cues were comprehended in terms of egocentric reference systems, whereas iconic arrows were not.     

Visual motion interferes with tactile motion perception

Previous studies have demonstrated that visual apparent motion can alter the judgment of auditory apparent motion. We investigated the effect of visual apparent motion on judgments of the direction of tactile apparent motion. When visual motion was presented at the same time as, but in a direction opposite to, tactile motion, accuracy in judging the direction of tactile apparent motion was substantially reduced. This reduction in performance is referred to as 'the congruency effect'. Similar effects were observed when the visual display was placed either near to the tactile display or at some distance from the tactile display (experiment 1). In experiment 2, the relative alignment between the visual and tactile directions of motion was varied. The size of the congruency effect was similar at 0 degrees and 45 degrees alignments but much reduced at a 90 degrees alignment. In experiment 3, subjects made confidence ratings of their judgments of the direction of the tactile motion. The results indicated that the congruency effect was not due to subjects being unsure of the direction of motion and being forced to guess. In experiment 4, static visual stimuli were shown to have no effect on the judgments of direction of the tactile stimuli. The extent to which the congruency effect reflects capture effects and is the result of perceptual versus post-perceptual processes is discussed.     

Alcohol and motion perception

Three motion perception skills were measured under different levels of alcohol ingestion. Our method for detecting decrements in visual information processing proved sensitive to blood alcohol levels as low as .02%. Alcohol in small doses increased reaction times to the onset of motion, particularly to slow speeds, but did not reduce the ability to allocate attention effectively. In view of these findings, certain motion perception tests may be valuable assays for detecting impaired performance with low blood alcohol levels.     

Orientation specificity in biological motion perception

We addressed the issue of how display orientation affects the perception of biological motion. In Experiment 1, spontaneous recognition of a point-light walker improved abruptly with image-plane display rotation from inverted to upright orientation. Within a range of orientations from 180 degrees to 90 degrees, it was dramatically impeded. Using ROC analysis, we showed (Experiments 2 and 3) that despite prior familiarization with a point-light figure at all orientations, its detectability within a mask decreased with a change in orientation from upright to a range of 90 degrees-180 degrees. In Experiment 4, a priming effect in biological motion was observed only if a prime corresponded to a range of deviations from upright orientation within which the display was spontaneously recognizable. The findings indicate that display orientation nonmonotonically affects the perception of biological motion. Moreover, top-down influence on the perception of biological motion is limited by display orientation.     

Concurrent motion in infant event perception

Infant sensitivity to motion relationships specifying certain complex events, such as a person walking, has recently been demonstrated, but the perceptual principles underlying early event perception are not well understood. Retinal motion toward a common point (concurrent motion) specifies translation in depth to adult perceivers in the absence of conflicting information (Börjesson & von Hofsten, 1973). We tested this principle of event perception with 28 16-week-old infants. One group was habituated in a dark room to a concurrent motion: three points of light moving in a frontoparallel plane toward and away from a central point (not seen). After habituation, the room was illuminated, and looking time was tested to alternate presentations of two displays. In one display (depth motion), three lights were attached to a triangle actually moving in depth; in the other display (surface motion), the three lights moved visibly along the surface of a fronto-parallel stationary triangle. If concurrent motion, in the absence of conflicting information, specifies motion in depth to infants, they were expected to look longer after habituation at the surface motion display. A control group tested infants' relative interest in the two test displays with no prior habituation period.Control-group infants marginally preferred the depth movement display. The habituation group responded three times as much to the surface motion display, suggesting that motion in depth had been perceived during habituation. Specification of motion in depth by concurrency of relative proximal stimulus motions seems to be an operative principle in infants' perception; moreover, at least some principles of early event perception are unrelated to person perception or biological motion. The relation of these results to recent findings in infant object perception is discussed.     

Frames of reference for anticipatory action in 4-month-old infants

The spatial representations of 4-month-old infants were examined in two experiments using a modified version of the visual expectation paradigm (VExP). The experiments were designed in order to determine what spatial frames of reference were available to infants for making anticipatory saccades. In Experiment 1, we found that infants most often used a retinocentric frame of reference that did not take into account their current eye position in making an anticipatory saccade. However, Experiment 2 revealed that under certain conditions infants are more likely to make anticipatory saccades consistent with a body- or object-centred frame of reference. The main difference between the two experiments was the degree to which the featural properties of the stimuli varied. The results shed light on the development of spatial representations for action in infancy.