When a video of someone speaking is paused, the stationary image of the speaker typically appears less flattering than the video, which contained motion.We call this the frozen face effect (FFE).Here we report six experiments intended to quantify this effect and determine its cause.In Experiment 1, video clips of people speaking in naturalistic settings as well as all of the static frames that composed each video were presented, and subjects rated how flattering each stimulus was.The videos were rated to be significantly more flattering than the static images, confirming the FFE.In Experiment 2, videos and static images were inverted, and the videos were again rated as more flattering than the static images.In Experiment 3, a discrimination task measured recognition of the static images that composed each video.Recognition did not correlate with flattery ratings, suggesting that the FFE is not due to better memory for particularly distinct images.In Experiment 4, flattery ratings for groups of static images were compared with those for videos and static images.Ratings for the video stimuli were higher than those for either the group or individual static stimuli, suggesting that the amount of information available is not what produces the FFE.In Experiment 5, videos were presented under four conditions: forward motion, inverted forward motion, reversed motion, and scrambled frame sequence.Flattery ratings for the scrambled videos were significantly lower than those for the other three conditions.In Experiment 6, as in Experiment 2, inverted videos and static images were compared with upright ones, and the response measure was changed to perceived attractiveness.Videos were rated as more attractive than the static images for both upright and inverted stimuli.Overall, the results suggest that the FFE requires continuous, natural motion of faces, is not sensitive to inversion, and is not due to a memory effect.

Peripheral objects and their features become indistinct when closely surrounding but nonoverlapping objects are present. Most models suggest that this phenomenon, called crowding, reflects limitations of visual processing, but an intriguing idea is that it may be, in part, adaptive. Specifically, the mechanism generating crowding may simultaneously facilitate ensemble representations of features, leaving meaningful information about clusters of objects. In two experiments, we tested whether visual crowding and the perception of ensemble features share a common mechanism. Observers judged the orientation of a crowded bar, or the ensemble orientation of all bars in the upper and lower visual fields. While crowding was predictably stronger in the upper relative to the lower visual field, the ensemble percept did not vary between the visual fields. Featural averaging within the crowded region does not always scale with the resolution limit defined by crowding, suggesting that dissociable processes contribute to visual crowding and ensemble percepts.

Visually perceived eye level (VPEL) and perceived pitch were measured while subjects viewed two sets of stimuli that were either upright or pitched top-toward or top-away from them. The first set of stimuli, a pair of vertical lines, caused systematic changes in perceived pitch and upward and downward VPEL shifts for the top-toward and top-away pitches, respectively. Neither the perceived pitch nor the VPEL measures with these stimuli differed between monocular and binocular viewing. The second set of stimuli was constructed so that when viewed at the appropriate pitch angle, the slopes of the lines in the retinal image of each stimulus were similar to those generated by a pair of vertical lines pitched symmetrically in the opposite direction. When viewed monocularly, these stimuli appeared pitched in the direction opposite their physical pitch, yet produced VPEL shifts consistent with the direction of their physical pitch. These results clearly demonstrate a dissociation between perceived pitch and VPEL. The same stimuli, when viewed binocularly, appeared pitched in the direction of their physical pitch and caused VPEL shifts consistent with this pitch direction. The retinal images of these stimuli, however, corresponded to those of vertical line stimuli pitched in the opposite direction. This finding is therefore inconsistent with the hypothesis that VPEL is determined solely on the basis of the orientation of lines in the retinal image.

In three experiments subjects tracked a dot that oscillated vertically while a rectangular stimulus oscillated horizontally. The pairing of frame and dot motion caused the dot to appear to move on a slant due to induced motion (IM). In the first experiment, subjects made judgments of the apparent slant of the dot's motion and, on separate trials, pointed open loop at the apparent location of the dot at the endpoints of its motion. Both responses were influenced by IM, although the influence on dot location was less than the amount of IM indicated by the slant responses. Results were similar immediately following IM and after a five second delay. In the second experiment, subjects pointed open loop either at the apparent location of the endpoints of the tracked dot's motion or at the apparent location of one of three other briefly flashed dot targets. The pointing responses directed toward the fixated IM target were influenced by IM, although there was no similar influence on responses directed toward the other three targets. In the third experiment, similar measures were obtained while subjects maintained fixation at the location of the tracked dot. Results were similar to those obtained in the second experiment. The results of the three studies are inconsistent with the hypotheses that IM alters the registration of either eye position or trunk position, as misregistration of either would be expected to influence pointing responses directed to either the tracked stimulus or the other briefly flashed targets.

Reaching toward a cup of coffee while reading the newspaper becomes exceedingly difficult when other objects are nearby. Although much is known about the precision of visual perception in cluttered scenes, relatively little is understood about acting within these environments - the spatial resolution of visuomotor behavior. When the number and density of objects overwhelm visual processing, crowding results, which serves as a bottleneck for object recognition. Despite crowding, featural information of the ensemble persists, thereby supporting texture perception. While texture is beneficial for visual perception, it is relatively uninformative for guiding the metrics of grasping. Therefore, it would be adaptive if the visual and visuomotor systems utilized the clutter differently. Using an orientation task, we measured the effect of crowding on vision and visually guided grasping and found that the density of clutter similarly limited discrimination performance. However, while vision integrates the surround to compute a texture, action discounts this global information. We propose that this dissociation reflects an optimal use of information by each system.

This research examined motor measures of the apparent egocentric location and perceptual measures of the apparent allocentric location of a target that was being seen to undergo induced motion (IM). In Experiments 1 and 3, subjects fixated a stationary dot (IM target) while a rectangular surround stimulus (inducing stimulus) oscillated horizontally. The inducing stimulus motion caused the IM target to appear to move in the opposite direction. In Experiment 1, two dots (flashed targets) were flashed above and below the IM target when the surround had reached its leftmost or rightmost displacement from the subject’s midline. Subjects pointed open-loop at either the apparent egocentric location of the IM target or at the bottom of the two flashed targets. On separate trials, subjects made judgments of the Vernier alignment of the IM target with the flashed targets at the endpoints of the surround’s oscillation. The pointing responses were displaced in the direction of the previously seen IM for the IM target and to a lesser degree for the bottom flashed target. However, the allocentric Vernier judgments demonstrated no perceptual displacement of the IM target relative to the flashed targets. Thus, IM results in a dissociation of egocentric location measures from allocentric location measures. In Experiment 2, pointing and Vernier measures were obtained with stationary horizontally displaced surrounds and there was no dissociation of egocentric location measures from allocentric location measures. These results indicate that the Roelofs effect did not produce the pattern of results in Experiment 1. In Experiment 3, pointing and Vernier measures were obtained when the surround was at the midpoint of an oscillation. In this case, egocentric pointing responses were displaced in the direction of surround motion (opposite IM) for the IM target and to a greater degree for the bottom flashed target. However, there was no apparent displacement of the IM target relative to the flashed targets in the allocentric Vernier judgments. Therefore, in Experiment 3 egocentric location measures were again dissociated from allocentric location measures. The results of this experiment also demonstrate that IM does not generate an allocentric displacement illusion analogous to the “flash-lag” effect.

We compared the resting (dark) focus of accommodation before and after adapting to accommodative stimuli placed nearer or farther from an initial baseline resting focus. Short‐term monocular adaptation (< 2 min) did not result in consistent after‐effects that were correlated with the adaptation stimulus. After short‐term adaptation, accommodation returned to its resting level in 2–15s. Long‐term monocular adaptation (30 min) to a 6‐D near stimulus resulted in a small (0.5‐D) average increase in the resting focus of accommodation beyond the normal 2–15‐s short‐term decay. These observations illustrate a tonic adaptation of accommodation that is small and requires longer durations of adaptation than an analogous adaptation of the fusional vergence system to prism.

Previous investigations have shown that, in dim illumination and empty visual fields, accommodation in most observers is for an intermediate distance referred lo as the dark focus or resting focus of accommodation. Dynamic properties of the resting focus were examined in the present study with a high‐speed infrared optometer. All subjects displayed fluctuations of accommodation in darkness that were primarily characterized by frequency components below 0.5 Hz. These fluctuations were substantially attenuated during cycloplegia or viewing a bright, high‐contrast target. Both the mean resting‐focus position and the magnitude of fluctuations varied from one subject to another and from day‐to‐day. A weak association was found between the mean and standard deviation of accommodation responses in the dark. The present findings suggest that the accommodation mechanism in most observers is somewhat unstable under degraded viewing conditions. In addition, the mean resting‐focus value for a large sample of subjects was found to be lower for i.r. optometer measurements than for previous investigations employing a laser optometer.

The resting focus of accommodation was measured in the same subjects with both a laser optometer and a high-speed infrared optometer. Although i.r. optometer and laser optometer measures produce similar estimates of the mean resting-focus level in some subjects, others were found to have different levels of resting focus with the two techniques. Control studies demonstrated that these differences were not due to the temporal sampling characteristics of the laser optometer, but resulted instead from making judgments about the direction of speckle motion during the laser optometer procedure. The temporal stability of the resting focus of accommodation was also investigated with i.r. measures obtained several minutes, 1 day, and 1 and 2 weeks apart. Results indicated long-term variability similar to that previously reported with the laser optometer.

Four experiments examined the biases of individual subjects when attempting to bisect vertical lines, and tested various hypotheses concerning the origin of vertical bisection errors (VBEs). In each experiment, individual differences on the vertical line bisection task were compared to individual differences on another task to evaluate whether the tasks were systematically related. In the first experiment, VBEs were found not to correlate with horizontal line bisection errors (HBEs). In the second experiment, VBEs were found not to correlate with the size of the horizontal-vertical illusion (HVI). In the third experiment, VBEs were found not to correlate with differences in perceived length of vertical lines presented in the upper and lower visual fields that were displaced horizontally. In the fourth experiment, VBEs were found to correlate with bisection errors of an open vertical interval. The results of the first three studies are counter to various hypotheses of the origins of vertical bisection errors. The last experiment suggests that lines, per se, are unnecessary for VBEs. Rather, it is important that the upper and lower segments of the stimulus that are judged to be equal on vertical bisection tasks are co-extensive.

We examined the apparent dissociation of perceived length and perceived position with respect to the Müller-Lyer (M-L) illusion. With the traditional (two-chevron) figure, participants made accurate open-loop pointing responses at the endpoints of the shaft, despite the presence of a strong length illusion. This apparently non-Euclidean outcome replicated that of Mack, Heuer, Villardi, and Chambers (1985) and Gillam and Chambers (1985) and contradicts any theory of the M-L illusion in which mislocalization of shaft endpoints plays a role. However, when one of the chevrons was removed, a constant pointing error occurred in the predicted direction, as well as a strong length illusion. Thus, with one-chevron stimuli, perceived length and location were no longer completely dissociated. We speculated that the presence of two opposing chevrons suppresses the mislocalizing effects of a single chevron, especially for figures with relatively short shafts.

In the present research, we examined the influence of induced motion (IM) on open-loop pointing responses and the possibility that IM alters the registration of either eye or trunk position. In two experiments, subjects tracked a dot that oscillated vertically while a rectangular stimulus oscillated horizontally. The pairing of frame and dot motion caused the dot to appear to move on a slant, due to IM. In the first experiment, the subjects made judgments of the apparent slant of the dot's motion and, on separate trials, pointed open loop at the apparent location of the dot at the endpoints of its motion. Both responses were influenced by IM, although the effect on dot localization was less than the amount predicted by the IM, as indicated by the slant responses. Results were similar immediately following IM and after a 5-sec delay. In the second experiment, the subjects pointed open loop either at the apparent location of the endpoints of the tracked dot's motion or at the apparent location of one of three other briefly flashed stationary dots. The pointing responses directed toward the fixated IM target were influenced by IM to a greater extent than the responses directed toward the stationary dots. The results of the two experiments are inconsistent with the hypothesis that the effect of IM on open-loop pointing at the IM target results completely from altered perception of either eye or trunk position, since misregistration of either would be expected to influence, in a similar fashion, pointing at both the tracked dot and the briefly flashed, stationary targets.

Visual illusions have often been reported to have less of an effect on motor responses directed toward the stimulus display than might be predicted on the basis of the magnitude of the illusion. The present research examined whether the rod-and-frame effect (RFE) would display a similar pattern of apparent dissociation between vision and action. In the first experiment, the influences of frame orientation on both the perceived slope of a rod and on open loop pointing responses directed at the ends of the rod were measured. Frames rotated 22.5 deg clockwise and counterclockwise caused the rod to be perceived as tilted in the direction opposite the frame orientation (the RFE). Open loop pointing directed toward the ends of the rod was intermediate to the perceived and physical orientations of the rod, a result consistent with a partial dissociation of vision and action. In the second experiment, pointing responses were obtained either while the display was viewed concurrently or five to twenty seconds following eye closure. The results following the delay were highly similar to the results obtained with concomitant pointing. These findings suggest that during the delay, the motor system maintained a representation of the rod's true orientation to direct action, and did not come to rely to a greater degree on the memory of perceived orientation.

Visually perceived eye level (VPEL) and perceived pitch were measured while subjects viewed two sets of stimuli that were either upright or pitched top-toward or top-away from them. The first set of stimuli, a pair of vertical lines viewed at various angles of pitch, caused systematic changes in perceived pitch and upward and downward VPEL shifts for the top-toward and top-away pitches, respectively Neither the perceived pitch nor the VPEL measures with these stimuli differed between monocular and binocular viewing. The second set of stimuli was constructed so that, when viewed at the appropriate pitch angle, the projected orientations of the lines in the retinal image of each stimulus were similar to those generated by a pair of vertical lines pitched by a lesser amount in the opposite direction. When viewed monocularly, these stimuli appeared pitched in the direction opposite their physical pitch, yet produced VPEL shifts consistent with the direction of their physical pitch. These results clearly demonstrate a dissociation between perceived pitch and VPEL. The same stimuli, when viewed binocularly, appeared pitched in the direction of their physical pitch and caused VPEL shifts indistinguishable from those obtained monocularly. The retinal image orientations of these stimuli, however, corresponded to those of vertical line stimuli pitched in the opposite direction. This finding is therefore consistent with the hypothesis that VPEL and perceived pitch are processed independently, but inconsistent with the specific version of this hypothesis which states that differences in VPEL are determined solely on the basis of the orientation of lines in the retinal image.

In two experiments, normal adults divided a horizontal line segment and an equal spatial interval that did not contain a line into eight equal-appearing segments by means of successive bisections. In the first experiment, subjects' average initial bisections erred to the left of objective center for both stimuli. Their subsequent bisections produced similar errors for the line-present stimulus, as the bisection of each progressively smaller line segment was placed to the left of true center. However, this pattern did not occur when bisecting the empty interval. The finding that the presence of a line influences bisection errors implicates an 'object-based' mechanism in the genesis of line bisection errors and suggests that this mechanism varies in its operation with visual field location. In the second experiment, subjects successively bisected longer line and interval stimuli which were presented either centered on the subjects' midlines or displaced to the right or left. Bisections tended to be placed farther to the left for the left stimuli and farther to the right for the right stimuli, with little or no bias for the centrally located stimuli. Repeated measures with the centrally located stimulus demonstrated strong individual differences in bisection biases. Errors were also found to be correlated for the line-present and line-absent stimuli in both experiments, suggesting the additional contribution of a mechanism that is not object-based.

In two experiments, visually perceived eye level (VPEL) was measured while subjects viewed two-dimensional displays that were either upright or pitched 20° top-toward or 20° top-away from them. In Experiment 1, it was demonstrated that binocular exposure to a pair of pitched vertical Unes or to a pitched random dot pattern caused a substantial upward VPEL shift for the top-toward pitched array and a similarly large downward shift for the top-away array. On the other hand, the same pitches of a pair of horizontal lines (viewed binocularly or monocularly) produced much smaller VPEL shifts. Because the perceived pitch of the pitched horizontal line display was nearly the same as the perceived pitch of the pitched vertical line and dot array, the relatively small influence of pitched horizontal Unes on VPEL cannot be attributed simply to an underestimation of their pitch. In Experiment 2, the effects of pitched vertical lines, dots, and horizontal lines on VPEL were again measured, together with their effects on resting gaze direction (in the vertical dimension). As in Experiment 1, vertical lines and dots caused much larger VPEL shifts than did horizontal lines. The effects of the displays on resting gaze direction were highly similar to their effects on VPEL. These results are consistent with the hypothesis that VPEL shifts caused by pitched visual arrays are due to the direct influence of these arrays on the oculomotor system and are not mediated by perceived pitch.

OBJECTIVE:Transient visual events cause a rapid allocation of attention to the event location. We studied the effect of alcohol on this aspect of attention.METHOD:Subjects responded to targets presented either left or right of fixation and the time between target presentation and response (reaction time: RT) was measured both before and after ingestion of either alcohol or a placebo. Transient cues were presented prior to each target presentation. Cues were, variously, a brightening of either the box in which the target was to occur ("valid"), the box on the opposite side of the display from where the target was to occur ("invalid") or the fixation stimulus ("neutral"). The interval between cue and target presentation (stimulus onset asynchrony: SOA) was variously 50, 100, 150 or 800 msecs.RESULTS:At short SOAs, RT was faster to targets presented following valid cues relative to the other cues. At 800 msecs the opposite pattern was found. Alcohol selectively slowed RT only following neutral or invalid cues at short SOAs.CONCLUSIONS:Alcohol does not disrupt the normal attentional allocation to visual transients. It may delay the subsequent response to events at other locations, however.

OBJECTIVE The contributions of feedback to formation of acute ethanol tolerance were studied during performance of a task that allowed practice in the absence of feedback about performance accuracy. METHOD The perceptual instability of the seen environment during head movement (apparent concomitant motion, ACM) and the vestibulo-ocular reflex (VOR) were measured before and after alcohol ingestion. In separate conditions, eight (six female) subjects were either deprived or not deprived of normal vision of the laboratory during the portion of the experiment following onset of alcohol ingestion. RESULTS Alcohol caused ACM in the direction opposite head rotation to increase in both sessions. The degree of ACM increase was greater during sessions in which visual feedback was prevented than in sessions in which subjects could see the surroundings. The increase in ACM was accompanied by a decrease in gain of the VOR which was relatively larger in the no-feedback condition. In addition, ACM returned to normal (pre-alcohol ingestion) values more rapidly during sessions in which subjects received visual feedback. CONCLUSIONS The results suggest that feedback is an important component in forming acute tolerance to alcohol, independent of task practice.