Light Point Research Articles

Two Anecdotes of Pie

Two Anecdotes of Pie Donald Platt I Wallace Stevens lovedpie. His neighbor brought him a chocolatesilk pie, dark as a starless night. “What do youcall this pie?” he asked, he who had “placed a jarin Tennessee.” She smiled and replied,“Heavenly Pie.” That jar had tamed “the slovenlywilderness” around him. “Well,” he said,raising a piece on his fork slowly towardshis mouth, hungry after having walked home froma long day writing surety bonds at theHartford Accident and IndemnityCompany on Asylum Avenue,“Open the pearly gates.” II I am so loved byyou, who walk through rain [End Page 106] for twenty minutesto my apartment, carrying ina glass pie pan wrapped in a soft burlapbag to keep it warm from the oven, onewhole, paw-paw, lemon grass, and ginger pie.You grew the paw-paws, shook them when ripe downfrom the tree. Deseeded them. Scooped out theirbutter-colored flesh. Puréed it. Mixed itwith vanilla sugar, spices, whole milk, eggs.Poured it into its graham-cracker crust.Baked it until it turned golden as theharvest moon rising over a lake, castingits moonlight on the dark water to makean upside-down exclamation pointof light the color of gnarled ginger root.You are allergic [End Page 107] to paw-paws. You stayhungry and smile while you watch me devour onelarge slice, then clamor for more caramelizedmoonlight. [End Page 108] Donald Platt Lafayette, Indiana Copyright © 2023 Johns Hopkins University Press

Brain Activation During Visually Guided Finger Movements.

Computer interaction via visually guided hand movements often employs either abstract cursor-based feedback or virtual hand (VH) representations of varying degrees of realism. The effect of changing this visual feedback in virtual reality settings is currently unknown. In this study, 19 healthy right-handed adults performed index finger movements (“action”) and observed movements (“observation”) with four different types of visual feedback: a simple circular cursor (CU), a point light (PL) pattern indicating finger joint positions, a shadow cartoon hand (SH) and a realistic VH. Finger movements were recorded using a data glove, and eye-tracking was recorded optically. We measured brain activity using functional magnetic resonance imaging (fMRI). Both action and observation conditions showed stronger fMRI signal responses in the occipitotemporal cortex compared to baseline. The action conditions additionally elicited elevated bilateral activations in motor, somatosensory, parietal, and cerebellar regions. For both conditions, feedback of a hand with a moving finger (SH, VH) led to higher activations than CU or PL feedback, specifically in early visual regions and the occipitotemporal cortex. Our results show the stronger recruitment of a network of cortical regions during visually guided finger movements with human hand feedback when compared to a visually incomplete hand and abstract feedback. This information could have implications for the design of visually guided tasks involving human body parts in both research and application or training-related paradigms.

Observation of the point-light animation of a grasping hand activates sensorimotor cortex in nine-month-old infants

Measuring changes in sensorimotor alpha band activity in nine-month-old infants we sought to understand the involvement of the sensorimotor cortex during observation of the Point-Light (PL) animation of a grasping hand. Attenuation of alpha activity was found both when the PL display moved towards the to-be-grasped object and when the object was deleted from the video. Before the beginning of the movement of the PL stimuli, only in the presence of the object evoked attenuation of sensorimotor alpha activity was documented, possibly interpreted either as movement prediction or as graspable object perception. Our main findings demonstrate that, during observation of stimuli moving with biological kinematics, the infants' sensorimotor system is activated when the pictorial information is absent or highly reduced, and independently of the presence of the goal-directed object. The possible compensatory function of the sensorimotor system during observation of highly degraded moving stimuli is discussed.

Perception of another person's maximum reach-with-jump height from walking kinematics.

Humans can perceive affordances (possibilities for action) for themselves and others, including the maximum overhead height reachable by jumping (reach-with-jump height, RWJ). While observers can accurately perceive maximum RWJ for another person without previously seeing the person jump, estimates improve after viewing the person walk, suggesting there is structure in walking kinematics that is informative about the ability to produce vertical force for jumping. We used principal component analysis (PCA) to identify patterns in human walking kinematics that specify another person's maximum RWJ ability, and to determine whether athletes are more sensitive than non-athletes to these patterns. Kinematic data during treadmill walking were collected and submitted to PCA to obtain loading values for the kinematic time series variables on the first principal component. Kinematic data were also used to create point-light (PL) displays, in which the movement kinematics of PL walkers were manipulated using the obtained PCA loading values to determine how changes in body-segment movements impacted perception of maximum RWJ height. While manipulating individual segmental loadings in the PL displays did not substantially affect RWJ estimates, PL displays created by replacing the PCA loadings of a high-jumper with those of a low-jumper, and vice versa, resulted in corresponding reversals of participants' RWJ estimates, suggesting that the global structure of walking kinematics carries information about another's maximum RWJ height. Athletes exhibited greater sensitivity than controls to the kinematic manipulations, indicating that they are better attuned to useful kinematic information as a result of their sport experience.

Walking my way? Walker gender and display format Confounds the perception of specific emotions

Previous evidence has shown that males and females display different gait kinematics which may influence the perception of emotions displayed through the same walking gait. We therefore investigated the influence of walker gender on the perception of happiness, sadness, anger and fear displayed through walking movements. Full-light (FL), point-light (PL) and synthetically modelled point-light walkers (SW) of both genders were shown to perceivers over three experiments. Additionally, gender ambiguous synthetic walkers were shown to control for the influence of form, gender stereotypes and idiosyncratic gait movements on emotional gait perception. Each emotion was identified above chance level for both walker genders and in all display conditions though significantly less in PL and SW than in FL. The gender of the walker did not influence the pattern of identifications in FL walkers (Fear > Sad > Happy > Anger > Neutral), but did influence the identification patterns in PL (Female: [Happy = Sad = Fear = Anger] > Neutral; Male: Fear = Sad = [Happy > Anger] > Neutral) and SWs (Female: Happy = Sad = Anger = Fear = Neutral; Male: [Happy = Sad = Anger] > [Fear = Neutral]; Ambiguous: [[Happy = Sad = Anger] > Fear] = Neutral). The gender of the walker and format in which they are displayed influenced the perception of different basic emotions. The constructed SW stimuli also displayed happiness, sadness and anger with equivalent intensity in female, male and gender ambiguous walkers thus untangling the perception-expression entanglement that has plagued previous emotion perception research.

A Design Method for LEDs Arrays Structure Illumination

Capturing high quality image is very important in the active automatic optical inspection system. Besides camera, image quality mainly is affected by the illumination. A design method of structure illumination, which is comprised of light emitting diodes (LEDs) arrays, is proposed in this paper. And especially, these LEDs arrays are not in the same plane. First, the single LED irradiating model is built based on analyzing its irradiance properties. Second, the case of two LEDs irradiating is set as an example to analyze superposition properties of the same color light for any specified point's light brightness based on the built single LED irradiating model, and then the irradiating model of LEDs is developed. Third, the structure illumination design method of LEDs ring arrays is illustrated based on the proposed design model of illumination uniformity. Especially, the illumination design method is decomposed into two subproblems to simplify the design process, which can reduce the design difficulty. Experimental results show that the light intensity deviation is less than 3.78% by the proposed illumination design method, which validates the effectiveness of the proposed method.

A new technique for generating disordered point-light animations for the study of biological motion perception.

Studies of biological motion perception often use stimuli depicting human actions portrayed via point-light (PL) displays. Typically, counterpart, or control, stimuli for PL biological motion are created by spatially scrambling motion trajectories of individual PL dots. Depending on the purpose of the study, however, this procedure may be inappropriate as a foil for genuine PL animations, because spatial scrambling not only disrupts coherent motion activity but also eliminates pair-wise motion relationships among dots and, unless corrected, alters the spatial spread of PL dot motions. We introduce a new technique for producing perturbed PL animations, called pair-wise shuffled motion, that preserves the elementary features of biological motion in spatial and motion energy domains and only disrupts the specific sense of global, coherent perception of biological motion. First we describe the procedure for creating pair-wise shuffled motion sequences. Next we compare unperturbed PL animations to pair-wise shuffled motion, to spatially scrambled motion, and to spatially constrained scrambled motion in terms of spatial distributions of the dots, spatiotemporal amplitude spectra derived from Fourier analysis of those sequences, and space-time motion energy associated with those perturbed animations. We then show that the results from those analyses generalize to a large family of PL animations, including the widely used PL walker. Finally we present results from a two-interval forced-choice biological-motion discrimination experiment comparing the robustness of scrambled and pair-wise shuffled motions as foil stimuli. Results from these comparisons suggest that pair-wise shuffled motion offers advantages as a foil stimulus compared to foils using the conventional scrambling technique. Pair-wise shuffled motion provides an additional, effective control display for evaluating PL biological motion perception in future psychophysical, computational, and imaging studies that focus on mechanisms of processing spatiotemporal information signifying biological motion within PL displays.

Assessing audiovisual saliency and visual-information content in the articulation of consonants and vowels on audiovisual temporal perception

Research has revealed different temporal integration windows between and within different speech-tokens. The limited speech-tokens tested to date has not allowed for the proper evaluation of whether such differences are task or stimulus driven? We conducted a series of experiments to investigate how the physical differences associated with speech articulation affect the temporal aspects of audiovisual speech perception. Videos of consonants and vowels uttered by three speakers were presented. Participants made temporal order judgments (TOJs) regarding which speech-stream had been presented first. The sensitivity of participants’ TOJs and the point of subjective simultaneity (PSS) were analyzed as a function of the place, manner of articulation, and voicing for consonants, and the height/backness of the tongue and lip-roundedness for vowels. The results demonstrated that for the case of place of articulation/roundedness, participants were more sensitive to the temporal order of highly-salient speech-signals with smaller visual-leads at the PSS. This was not the case when the manner of articulation/height was evaluated. These findings suggest that the visual-speech signal provides substantial cues to the auditory-signal that modulate the relative processing times required for the perception of the speech-stream. A subsequent experiment explored how the presentation of different sources of visual-information modulated such findings. Videos of three consonants were presented under natural and point-light (PL) viewing conditions revealing parts, or the whole, face. Preliminary analysis revealed no differences in TOJ accuracy under different viewing conditions. However, the PSS data revealed significant differences in viewing conditions depending on the speech token uttered (e.g., larger visual-leads for PL-lip/teeth/tongue-only views).

Comparing Biological Motion Perception in Two Distinct Human Societies

Cross cultural studies have played a pivotal role in elucidating the extent to which behavioral and mental characteristics depend on specific environmental influences. Surprisingly, little field research has been carried out on a fundamentally important perceptual ability, namely the perception of biological motion. In this report, we present details of studies carried out with the help of volunteers from the Mundurucu indigene, a group of people native to Amazonian territories in Brazil. We employed standard biological motion perception tasks inspired by over 30 years of laboratory research, in which observers attempt to decipher the walking direction of point-light (PL) humans and animals. Do our effortless skills at perceiving biological activity from PL animations, as revealed in laboratory settings, generalize to people who have never before seen representational depictions of human and animal activity? The results of our studies provide a clear answer to this important, previously unanswered question. Mundurucu observers readily perceived the coherent, global shape depicted in PL walkers, and experienced the classic inversion effects that are typically found when such stimuli are turned upside down. In addition, their performance was in accord with important recent findings in the literature, in the abundant ease with which they extracted direction information from local motion invariants alone. We conclude that the effortless, veridical perception of PL biological motion is a spontaneous and universal perceptual ability, occurring both inside and outside traditional laboratory environments.

Roles of the upper and lower bodies in direction discrimination of point-light walkers

We can easily recognize human movements from very limited visual information (biological motion perception). The present study investigated how upper and lower body areas contribute to direction discrimination of a point-light (PL) walker. Observers judged the direction that the PL walker was facing. The walker performed either normal walking or hakobi, a walking style used in traditional Japanese performing arts, in which the amount of the local motion of extremities is much smaller than that in normal walking. Either the upper, lower, or full body of the PL walker was presented. Discrimination performance was found to be better for the lower body than for the upper body. We also found that discrimination performance for the lower body was affected by walking style and/or the amount of local motion signals. Additional eye movement analyses indicated that the observers initially inspected the region corresponding to the upper body, and then the gaze shifted toward the lower body. This held true even when the upper body was absent. We conjectured that the upper body subserved to localize the PL walker and the lower body to discriminate walking direction. We concluded that the upper and lower bodies play different roles in direction discrimination of a PL walker.

Motor execution affects action prediction

Previous studies provided evidence of the claim that the prediction of occluded action involves real-time simulation. We report two experiments that aimed to study how real-time simulation is affected by simultaneous action execution under conditions of full, partial or no overlap between observed and executed actions. This overlap was analysed by comparing the body sides and the movement kinematics involved in the observed and the executed action. While performing actions, participants observed point-light (PL) actions that were interrupted by an occluder, followed by a test pose. The task was to judge whether the test pose depicted a continuation of the occluded action in the same depth angle. Using a paradigm proposed by Graf et al., we independently manipulated the duration of the occluder and the temporal advance of the test pose relative to occlusion onset (occluder time and pose time, respectively). This paradigm allows the assessment of real-time simulation, based on prediction performance across different occluder time/pose time combinations (i.e., improved task performance with decreasing time distance between occluder time and pose time is taken to reflect real-time simulation). The PL actor could be perceived as from the front or back, as indicated by task instructions. In Experiment 1 (front view instructions), evidence of action simulation was obtained for partial overlap (i.e., observed and performed action corresponded either in body side or movement kinematics), but not for full or no overlap conditions. The same pattern was obtained in Experiment 2 (back view instructions), ruling out a spatial compatibility explanation for the real-time pattern observed. Our results suggest that motor processes affect action prediction and real-time simulation. The strength of their impact varies as a function of the overlap between observed and executed actions.

Neural Integration of Information Specifying Human Structure from Form, Motion, and Depth

Recent computational models of biological motion perception operate on ambiguous two-dimensional representations of the body (e.g., snapshots, posture templates) and contain no explicit means for disambiguating the three-dimensional orientation of a perceived human figure. Are there neural mechanisms in the visual system that represent a moving human figure's orientation in three dimensions? To isolate and characterize the neural mechanisms mediating perception of biological motion, we used an adaptation paradigm together with bistable point-light (PL) animations whose perceived direction of heading fluctuates over time. After exposure to a PL walker with a particular stereoscopically defined heading direction, observers experienced a consistent aftereffect: a bistable PL walker, which could be perceived in the adapted orientation or reversed in depth, was perceived predominantly reversed in depth. A phase-scrambled adaptor produced no aftereffect, yet when adapting and test walkers differed in size or appeared on opposite sides of fixation aftereffects did occur. Thus, this heading direction aftereffect cannot be explained by local, disparity-specific motion adaptation, and the properties of scale and position invariance imply higher-level origins of neural adaptation. Nor is disparity essential for producing adaptation: when suspended on top of a stereoscopically defined, rotating globe, a context-disambiguated "globetrotter" was sufficient to bias the bistable walker's direction, as were full-body adaptors. In sum, these results imply that the neural signals supporting biomotion perception integrate information on the form, motion, and three-dimensional depth orientation of the moving human figure. Models of biomotion perception should incorporate mechanisms to disambiguate depth ambiguities in two-dimensional body representations.

The efficiency of biological motion perception

Humans can readily perceive biological motion from point-light (PL) animations, which create an image of a moving human figure by tracing the trajectories of a small number of light points affixed to a moving human body. We have applied ideal observer analysis to a standard biological motion discrimination task involving either full-figure or PL displays. Contrary to current dogma, we find that PL animations can be rich inpotential stimulus information but that human observers are remarkably inefficient at exploiting this information. Although our findings do not discount the utility of PL animation, they do provide a realistic measure of the computational challenge posed by biological motion perception.

Mr. Head's Journey to the Cross: Character, Structure, and Meaning in O'Connor's "The Artificial Nigger"

51 Marcia Smith Marzec Mr. Head's Journey to the Cross: Character, Structure, and Meaning in O'Connor's "The Artificial Nigger" Jesus is "SO SOUL hungry" that "he will chase [man] over the waters of sin" and "have him in the end," we are told in Flannery O'Connor's Wise Blood.1 God's Providential plan for human salvation , God's loving desire to bring man home to him, is, in fact, a major theme of O'Connor's Christian comedy. Again and again her fiction illustrates that even when man is engulfed in the darkness of disbelief, sin, and despair, God's plan is in progress, for the love of God is greater than human sinfulness. To illustrate God's transformation of apparent evil into a real and greater good, O'Connor purposely chooses what would seem the most unlikely agents for the salvation of her characters: the sociopathic Misfit of "A Good Man Is Hard to Find," who unwittingly prompts the Grandmother to her one moment of grace through love, thus becoming the instrument ofher salvation; or the self-blinding of Wise Blood's Hazel Motes, which allows him to see as St. Paul saw and to bring that point oflight to his landlady. This is also her technique in the "Artificial Nigger," in which she uses a Logos 1:3 1997 52 Logos southerner's very racism as a vehicle for his salvation. In this story, God reaches out to the major character with his offering of saving grace through the agency of a plaster statue, but it is only because of his racism that this character is able to receive God's message. Thus, O'Connor communicates her point that no one, no matter in what spiritual darkness, is beyond the pale of salvation. From the beginning of the story, O'Connor takes pains to depict Mr. Head unsympathetically. Not only is he an ignoramus and vulgarian, but he is, in fact, so deluded as to think himself a savant. He sees himself as having "that calm understanding of life that makes him a suitable guide for the young."2 The narrator ironically describes his eyes as having a look of"ancient wisdom as if they belonged to one of the great guides of men"3: he compares Head with Virgil, and even with the angel Raphael. As Marshall Bruce Gentry has pointed out, "[sjuch elevated comparisons are easily understood as the narrator's satirical exaggeration of Mr. Head's too-high opinion of himself."4 Head feels that his "will and strong character" are written in his features, but the reader perceives his "long tube-like face with a long rounded open jaw and a long depressed nose"5 as anything but impressive. Similarly, Mr. Head deludes himself concerning his motives for the trip to Atlanta with his grandson Nelson.6 He thinks ofthe trip "in moral terms": "It was to be a lesson that the boy would never forget. He was to find out from it that he had no cause for pride merely because he had been born in a city. He was to find out that the city was not a great place."7 Yet the very next sentence belies Head's motives: Mr. Head, we are told, "meant him to see everything there is to see in a city so that he would be content to stay at home for the rest of his life." We realize that Head's true motivation lies in his own insecurity and his fear of losing Nelson. It is clear from the text that Head's relationship with his daughter had been less than good, and he fears losing his grandchild to the big city as he'd lost Nelson's mother. Character, Structure, and Meaning in O'Connor's "The Artificial Nigger"53 The description of Nelson, coming from the viewpoint of Head, reflects this insecurity, with Head's resulting suspicion ofthe child and his need to belittle in order to control. While critics have been quick to see the irony in the way Head sees himself, they fail to recognize a similar irony in his judgment of Nelson. Taking seriously the...