The perceptual fate of letters in two kinds of apparent movement displays

Two experiments investigated the importance of figurai relationships among stimulus elements in the determination of the kind of motion perceived in bistable apparentovement displays. Stimulus frames containing the words MITE and ITEM were constructed in such a way that the letters I, T, and E appeared in corresponding locations while the M was in disparate locations between frames. When the frames were alternated with a 20-msec ISI, observers maintained local figurai identity in their percepts of apparent movement. However, when the frames were alternated with an 80-msec ISI, observers reported apparent movement of the entire groups of letters and thereby ignored figurai relationships in their percepts of apparent movement. In a second experiment, it was found that figurai nonidentity between elements of successive frames always resulted in apparent movement of a perceptual group or “blob” regardless of ISI. It is suggested that short-range apparent-movement percepts rely strongly upon figurai identity among corresponding stimulus elements, whereas long-range apparent-movement percepts do not.     

Spatial correspondence and relation correspondence: grouping factors that influence perception of the Ternus display

We cite two different perceptual-correspondence principles whose emphasis can help to disambiguate the otherwise ambiguous Ternus display in apparent movement (a display that can alternately be seen in one of two possible configurations). One of these principles is spatial correspondence, which emphasizes the maintenance of similar stimulus elements in given locations over time. The other principle is relation correspondence, which emphasizes the maintenance of the inter-organization of stimulus elements across frames. Each of four experiments reported here made use of a different stimulus feature (eg element color or element texture) to emphasize these different correspondence principles in Ternus displays. As predicted, an emphasis upon spatial correspondence resulted in an increase in reports of element movement compared to a featureless control condition. Emphasis on relation correspondence resulted in an increase in reports of group movement. Extensions and limitations of the use of these principles to explain apparent movement are discussed.     

Left-right visual field asymmetry in bistable motion perception

Twelve observers viewed two alternating frames, each consisting of three rectangular bars which were displaced laterally by one cycle in one frame with respect to the other. At long interframe intervals (IFIs) observers perceived a group of three elements moving as a whole (group movement), whereas with IFIs shorter than 40-60 ms the overlapping elements in each frame appeared stationary while the third element appeared to move from one end of the display to the other (end-to-end movement). The percentage of group movement responses in central viewing was compared to those obtained for stimulus presentation in the left and right visual fields (4 deg eccentricity), for opposite horizontal directions of motion. All ten right-handed subjects showed a left-field advantage in sensitivity to group movement. The two left-handed subjects showed a similar advantage in sensitivity with right-field presentation. The effects of monocular vision, hand used in the task, spatial frequency, and contrast on visual field asymmetry were all investigated in two right-handed subjects. None of these factors affected the left-right asymmetry.     

Effects of spatial parameters on the perceptual organization of a bistable motion display

In a dynamic visual display which consisted of two alternating frames, each with three line elements, the individual elements which possessed a high degree of spatial correspondence from one frame to the next were paired perceptually and moved about locally. Any remaining elements moved independently and followed different movement rules. When there was no high degree of spatial correspondence of any elements across frames, or when the interval of time between frames was long, the elements behaved as a perceptual unit and moved about as a group. The local pairings and movements appeared to be mediated by a process with different functional characteristics from those of the process which mediated the wholistic movement of the elements as a group.     

The discrimination of differences in duration of a thermal reinforcement

The sides of a contour square appear successively when context lines are presented one before and one after the square. As the interstimulus interval (ISI) between lines and square is increased to 140 msec, reports of succession increase. If the sides of the square are presented successively and interpart interval (IPI) varied by a single staircase method in order to determine a succession threshold, the average magnitude of this threshold varies as a function of ISI, decreasing up to 140 msec lSI. Each S, however, shows a maximum decrease in threshold between 80 and 120 msec. Reports of this illusion are not dependent on beta movement of either context lines or square.     

Induced movement-in-depth and induced changing-size elicited by a luminous rotating spiral

Induced movement-in-depth and induced changing-size are infrequently investigated forms of a phenomenon whereby movement is ascribed to a stationary stimulus. The present note concerns qualitative responses to a display designed to elicit both forms. The inducer was a two-arm luminous rotating linear-function spiral, and the stationary stimulus was an annulus concentric with the spiral; it was patterned with concentric luminous circles. Viewing was monocular. Among the findings, induced movement-in-depth was more frequently reported than induced changing-size, despite the lack of veridical movement-in-depth in the display. Possible lines of explanation are suggested.     

Visual apparent motion can be modulated by task-irrelevant lexical information

Previous studies have repeatedly demonstrated the impact of Gestalt structural grouping principles upon the parsing of motion correspondence in ambiguous apparent motion. Here, by embedding Chinese characters in a visual Ternus display that comprised two stimulus frames, we showed that the perception of visual apparent motion can be modulated by activation of task-irrelevant lexical representations. Each frame had two disks, with the second disk of the first frame and the first disk of the second frame being presented at the same location. Observers could perceive either "element motion," in which the endmost disk is seen as moving back and forth while the middle disk at the central position remains stationary, or "group motion," in which both disks appear to move laterally as a whole. More reports of group motion, as opposed to element motion, were obtained when the embedded characters formed two-character compound words than when they formed nonwords, although this lexicality effect appeared to be attenuated by the use of the same characters at the overlapping position across the two frames. Thus, grouping of visual elements in a changing world can be guided by both structural principles and prior world knowledge, including lexical information.     

The relationship between visual persistence and event perception in bistable motion display

Observers viewed two alternating frames, each consisting of three rectangular bars displaced laterally by one cycle in one frame with respect to the other. At long interframe intervals (IFIs) observers perceived a group of three bars moving as a whole (group motion), and at short IFIs the overlapping elements in the two frames appeared stationary, while the third element appeared to move from one end of the display to the other (element motion). The upper temporal limit for perceiving element motion was reduced when bars with blurred edges were used and when either frame duration or bar size was increased. However, when inner and outer elements had different sizes, the element motion percept was dominant up to 230 ms IFI. These findings may be interpreted in terms of spatial tuning of motion mechanisms involved in the perception of bistable apparent motion.     

Visible persistence and form correspondence in Ternus apparent motion.

Visual stimuli remain visible for some time after their physical offset (visible persistence). Visible persistence has been hypothesized to play an important role in determining the pattern of correspondence matching in the Ternus apparent-motion display. In this display, one or more elements reappears in overlapping locations at different times, whereas another element appears alternately to the right or the left of these elements. Usually either the elements are perceived to move coherently as a group (group motion), or one element may be perceived to hop over one or more other elements (element motion). According to the visible-persistence account of the perceptual organization of the Ternus display, element motion is seen when the temporal gap between elements in overlapping locations is small enough to be bridged by visible persistence; if it is not, group motion is seen. We conducted four experiments to test this visible-persistence account. In Experiments 1 and 2, a form correspondence cue (line length) was introduced to bias the visual system toward the element-motion interpretation, while visible persistence was either reduced or eliminated. The element-motion percept dominated despite the elimination of visible persistence. In Experiments 3 and 4, we found that Ternus elements presented without interruption, and thus presumably persisting over time, can be perceived in group motion. Together, the results indicate that visible persistence is neither necessary nor sufficient to account for the pattern of correspondence matches in the Ternus display.     

Number Judgment of Postage Stamps: A Contribution to the Psychology of Social Norms

PBI teems with unanswered questions regarding location, relative position, size, color, shape, movement, magnification, and what, precisely, is being observed. A novel experimental design is suggested which might permit sustained observation of PBI with use of facilitating flicker with a quasi-moving but motionless stimulus and a stationary eye.     

Discrimination of direction of movements in pigeons following previous experience of motion/static discrimination

Two experiments examined pigeons' discrimination of directional movement using pictorial images shown on computer monitors. Stimuli consisted of the movement of a bird against a stationary background or the movement of the background behind a stationary bird. In Experiment 1, pigeons were trained to discriminate either leftward or rightward motion of either the bird or the background from stationary frames drawn from the same movies. The background-discrimination group acquired the discrimination faster than the bird-discrimination group. In Experiment 2, transfer of the discrimination from the task of Experiment 1 to a discrimination between motion directions was examined. Most of the pigeons learned this discrimination rapidly, whereas in a pilot study in which direction discrimination was trained without previous static/movement discrimination, learning was poor. It appears that an experimental history of movement against stationary discrimination promoted the pigeons' learning of the directional motion discrimination.     

Visible persistence and form correspondence in Ternus apparent motion

Visual stimuli remain visible for some time after their physical offset (visible persistence) Visible persistence has been hypothesized to play an important role in determining the pattern of correspondence matching in the Ternus apparent-motion display. In this display, one or more elements reappears in overlapping locations at different times, whereas another element appears alternately to the right or the left of these elements. Usually either the elements are perceived to move coherently as a group (group motion), or one element may be perceived to hop over one or more other elements (element motion). According to the visible-persistence account of the perceptual organization of the Ternus display, element motion is seen when the temporal gap between elements in overlapping locations is small enough to be bridged by visible persistence; if it is not, group motion is seen. We conducted four experiments to test this visible-persistence account. In Experiments 1 and 2, a form correspondence cue (line length) was introduced to bias the visual system toward the element-motion interpretation, while visible persistence was either reduced or eliminated. The element-motion percept dominated despite the elimination of visible persistence. In Experiments 3 and 4, we found that Ternus elements presented without interruption, and thus presumably persisting over time, can be perceived in group motion. Together, the results indicate that visible persistence is neither necessary nor sufficient to account for the pattern of correspondence matches in the Ternus display.     

Spatial span under translation: A study of reference frames

The nature of the reference frame used to remember location sequences in a computer-presented version of spatial span was investigated by moving the template (a rectangular frame enclosing nine target squares) across the screen during presentation and/or during recall. Movement of the display during presentation substantially impaired memory in comparison with a stationary display (Experiment 1). However, there was no effect of template movement during recall (Experiment 2). In Experiments 3 and 4, the template was moved through the same screen locations during presentation and recall. When the extrinsic, or screen location, of each position was repeated identically on each trial but the sequence on the template varied, learning was not facilitated (Experiment 3). When the template sequences were repeated across trials but extrinsic location varied, the sequences were rapidly learned (Experiment 4). In this version of spatial span, location sequences appear to be encoded in an intrinsic frame of reference that is based on the template. Movement of the template during encoding impairs this process, possibly because concurrent attention shifts prevent the encoding of locations. The results are discussed with respect to recent studies of positional encoding in which multiple reference frames were available.     

The time course of figure-ground reversal

We report the results from five experiments employing a modified version of the short-term visual matching (STVM) method introduced by Driver and Baylis (1996). In STVM, participants see a study display with ambiguous figure-ground relations. After the study display, participants have to decide which of two shapes in a match display was seen before in the study display. STVM has been used by Vecera, Vogel, and Woodman (2002) to demonstrate that the lower region is a figure-ground cue. In our modified version of STVM, the study stimulus was preceded by a brief prime. This caused a biasing of the figural interpretation of the ambiguous figure-ground displays that contained the lower region cue. We show that 100-msec priming with an unambiguous display is enough to affect the subsequent interpretation of the ambiguous figure-ground display. It takes maximally 350 msec to complete a transition from the nondominant interpretation to the dominant interpretation of an ambiguous figure-ground display that contains the lower region cue.     

One-month-old human infants learn about the social world while they sleep

Although infants display preferences for social stimuli early in their lives, we know relatively little about the mechanisms of infant learning about the social world. In the current set of studies, 1-month-old infants underwent an adapted eyeblink conditioning paradigm to examine learning to both 'social' and non-social cues. While infants were asleep, they were presented with either a 'social' stimulus (a female voice) or one of two non-social stimuli (tone or backward voice) followed by an airpuff presented to the eyelid. Infants in the experimental groups displayed increased learning across trials, regardless of stimulus type. However, infants conditioned to the 'social' stimulus showed increased learning compared to infants conditioned to either of the non-social stimuli. These results suggest a mechanism by which learning about the social world occurs early in life and the power of ecologically valid cues in facilitating that learning.     

Induced rotary movement during eye movements: displays with unequal spacing of pattern

In my previous (Reinhardt-Rutland, 1982) study, I suggested that eye movements enhance induced rotary movement. However, low salience of absolute displacement might also explain the results, as displays were covered with large numbers of equally spaced radial pattern elements. To test these competing hypotheses in the present study, I used an unequally spaced pattern in two displays. Common to each display was an annulus: In one display, the common annulus surrounded a disk, and in the other display the common annulus was surrounded by another annulus. In any trial, one component rotated and the other was stationary while for 40 s the subject's eyes followed a circular path concentric with the display; subjects timed those occasions when perceived stronger rotation resided in the common annulus. Despite an unequally spaced pattern, absolute displacement had a barely significant effect. Instead, perceived stronger rotation mostly resided in a display's more central component. I concluded therefore that eye movements enhance induced rotary movement.     

Induced visual movement as nonveridical resolution of displacement ambiguity

Following the proposals made by Kinchla, it is argued that induced movement is a nonveridical resolution of stimulus ambiguity. The ambiguity derives from an identity between displacement of one element relative to another and displacement of the second relative to the first in a featureless field at velocities below the threshold for subject-relative movement. In such conditions, which element actually moves is perceptually unresolvable and veridical judgments therefore accord with chance. When a stationary field is introduced, perception is veridical, but when the field moves with the moving element, perception is nonveridical, i.e., induced movement of the stationary element and induced stationariness of the moving element occurs. The results from three experiments supported this interpretation and showed also that movement velocities above the subject-relative threshold contribute to the resolution of ambiguity.     

The stroop effect: Failure to focus attention or failure to maintain focusing?

Subjects matched the position (high or low) of a first stimulus with either the position or the meaning of a word (HI or LO) presented after an interstimulus interval (ISI). The form of the first stimulus (X or O) varied randomly within trial blocks and specified the relevant feature (meaning or position) of the second stimulus to the subject. When the relevant feature was meaning, Stroop interference from the second stimulus position was observed. This interference decreased as ISI increased. At the longest ISI, it was eliminated completely. A number of explanations for these effects are discussed and then tested in two further matching experiments. In a fourth experiment a similar decrease in interference was observed. These reductions in interference with increase in ISI appear to represent the development of attentional focusing on the relevant feature of the second stimulus. Stroop interference may occur in experiments where the relevant attribute is constant because of a difficulty associated with repeated focusing on the same attribute.     

Global cooperativity of the short-range process in apparent movement: evidence obtained with contour-containing stimuli

Previous research has demonstrated that the short-range process in apparent movement, as studied with random-dot cinematograms, exhibits global cooperativity; that is, computations performed by local elements interact nonlinearly and are pooled. Other research using displays containing extended contours has implicated the short-range process, but has never demonstrated global cooperativity. In the first of four experiments, it was shown that under certain conditions of presentation, a short-range motion percept exhibiting apparent global cooperativity can be obtained when collections of randomly located contours are rotated about the center of a display, despite the fact that the displacement of peripheral contours falls outside the normal limit of the short-range process. Experiments 2-4 were conducted to provide further evidence that the observed motion is short-range (i.e., it can be disrupted by illuminating the interstimulus interval or with dichoptic viewing) and that the percept is globally cooperative (i.e., masking the center of the display, where separations between corresponding elements across frames are smallest, results in a decline in the frequency of reports of the short-range percept). Control observations suggest that the effect produced with masks was not due to a decrease in the number of elements in the display. The argument that the display exhibits a short-range process with global cooperativity is further developed.     

Intramodal and crossmodal pairing and anchoring in comparisons of successive stimuli

Two experiments were conducted to study effects of modality, temporal position, and their interaction on comparisons of successive stimuli. In Experiment 1, intramodal (tone–tone and line–line) and crossmodal (tone–line and line–tone) stimulus pairs, with two interstimulus intervals (ISIs), 400 and 2,000 ms, were presented. Participants indicated which stimulus was the “stronger.” Time-order errors (TOEs) were assessed using the D% measure and were found in all types of pairs. Variation in TOEs across conditions was well accounted for by changes in parameters (stimulus weights, reference levels) in an extended version of Hellström’s sensation weighting (SW) model. With an ISI of 2,000 ms, the first stimulus had a lower weight (less impact on the response) than did the second stimulus. More negative TOEs were found with the longer ISI in all pair types except tone–line. In Experiment 2, participants indicated which of two lines was the longer or which of two tones was the louder. An intra- or crossmodal anchor, or no anchor, was interpolated between the stimuli. Anchoring tended to reduce the weight of the first stimulus, suggesting interference with memory, and to yield negative TOEs. Intramodal anchors yielded reduced weights of both stimuli, most dramatically for tones, suggesting an additional effect of stimulus interference. Response times decreased with crossmodal anchors. For line–line pairs, strong negative TOEs were found. In both experiments, the variation in TOE across conditions was well accounted for by the SW model.