动、静态视觉信息在真实世界视觉搜索中的作用

真实环境中的视觉搜索是人和动物赖以生存的重要能力。目前的视觉搜索研究多使用静态的观察者和静止的二维搜索对象, 侧重于探究注意在搜索中的作用; 现有的视觉搜索理论模型主要概括了影响搜索的自上而下的注意因素, 而将自下而上影响因素简单归结为影像显著性, 然而在真实环境中, 观察者或搜索对象是可以运动的, 搜索时可利用的视觉信息包括动态光流和静态影像结构信息。已有的视觉识别研究发现这两种信息相结合可以使观察者准确持久地识别场景、事件和三维结构。在现有视觉搜索理论模型中引入两种视觉信息可以较好还原真实环境中的搜索任务。我们提出研究构想和实验方案,探究利用动、静态视觉信息的视觉搜索过程, 从而完善现有的视觉搜索模型。我们认为充分利用环境信息可以提高搜索效率, 且在视觉搜索训练和智能搜索设计等方面有重要的应用价值。     

Preattentive Perception of Multiple Illusory Line-Motion: A Formal Model of Parallel Independent-Detection in Visual Search

The phenomenon referred to as illusory line-motion (ILM; O. Hikosaka, S. Miyauchi, & S. Shimojo, 1993a) has been described as a measure of the local facilitation of attention gradient. However, J. Kawahara, K. Yokosawa, S. Nishida, and T. Sato (1996) have demonstrated a spatially parallel search for an “odd man out” in the ILM direction. Apart from showing preattentive ILM perception in terms of an analogy between line-motion and apparent motion, the authors examined whether ILM perception is possible without attention from another point of view. Four experiments revealed that the ILM target can be detected in parallel without invoking attentional facilitation and invalidated the possible contribution of attentional set in parallel ILM search. Participants were able to correctly detect the ILM target among multiple nontargets, even when the line orientation was changed from trial to trial. The authors' independent-detection model predicted ILM search performance well on several occasions. These findings strongly support a preattentive and stimulus-driven explanation of ILM perception.     

Summarization of videos by analyzing affective state of the user through crowdsource

Video summarization is one of the key techniques to access and manage a huge chunk of videos. Video summarization is used to extract the effective contents of a video sequence to generate a concise representation of its content. The involvement of crowdsourcing models in recent years is effectively used by researchers in E-commerce domain to increase the quality of the data contents. In this paper, we present a video summarization framework based on users emotion while they watch videos by analyzing cerebral activities through Electroencephalogram (EEG) signals. Three emotions, namely happy, sad and neutral have been extracted from the EEG signals. Video frames have been synchronized with EEG signals and tagged with various emotions. Finally, a crowdsourcing model has been used for effective summarization of the videos. The qualitative assessment of video summarization has been conducted with the help of user ratings using online Google Forms application. EEG signals of 28 users have been recorded while video streams of different emotions. An average accuracy of 83.93% has been recorded in emotion classification using crowdsourcing. Output summarized videos include dynamic video skims and the corresponding audio stream for better understanding.     

Revisiting the metacontrast dissociation: Comparing sensitivity across different measures and tasks

In the metacontrast dissociation procedure, presenting a masked shape prime prior to a visible shape target leads to reaction-time effects of the prime in an indirect measure, although participants cannot consciously detect prime shapes in a direct measure (Klotz & Neumann, 1999 Klotz, W. and Neumann, O. 1999. Motor activation without conscious discrimination in metacontrast masking. Journal of Experimental Psychology: Human Perception and Performance, 25: 976–992.  [Google Scholar]). This has been taken as evidence for the processing of unconscious input. The results of the present metacontrast dissociation study indicate that although participants are unable to consciously report the shape of the prime, they can consciously perceive motion between masked primes and visible targets in a hybrid direct/indirect measure (Experiments 1 and 3). This indicates that former tests did not provide an exhaustive measure for residual conscious perception of the prime in the metacontrast dissociation procedure. Further tests, however, reveal that residual motion perception cannot account for performance in the indirect measure (Experiments 2 and 3). Although the results thus leave the conception of processing of unconscious input intact, they may prompt a revision of its criteria.     

Dynamic action in virtual environments: Constraints on the accessibility of action knowledge in children and adults

In a series of three experiments, we probed the accessibility of action knowledge in different versions of a virtual environment (VE) with 7-year-old children and adults. Using a PHANToM^TM haptic interface, participants performed a virtual throwing task in which they tried to propel a ball from a table to hit a target on the ground. In Experiments 1 and 2, the virtual scene was presented on a computer monitor, and, in Experiment 3, it was projected by using a video projector so that the vertical and horizontal dimensions and the spatial location of the VE corresponded to the real-world dimensions. Results indicate that action knowledge is accessible even in a nonimmersive VE, but also suggest that the need to recalibrate perceptual-motor mappings constrains the accessibility of this kind of intuitive knowledge.     

Methodological and empirical developments for the Ratcliff diffusion model of response times and accuracy

Summerfield, Egner, Mangels, and Hirsch (2006) suggested that visual misperception may be triggered by strong yet wrong expectation when sensory data are insufficient. Bar (2003) posits that immediately after stimulus presentation, low frequency spatial information (LFSI) convey the global form of the image which is matched to stored representations in the orbitofrontal cortex to generate predictions of the input. We used signal detection to test whether a strong prediction induced by informative global form, hence reducing the number of possible input matches, would facilitate recognition, but at the price of increasing the rate of misperceptions. Twenty-five participants were presented with target and foil images that shared global form, but differed in details. Pictures with informative global form resulted in higher confidence in recognition and shorter reaction times, but increased false alarms. Predictions of sensory input based on low frequency spatial information allow quick, facilitated recognition. However, the price for speed is the increased rate of misperceptions.     

The influence of motor expertise and motor experience on action and actor recognition

Two experiments examined whether different levels of motor and visual experience influence action perception and whether this effect depends on the type of perceptual task. Within an action recognition task (Experiment 1), professional basketball players and novice college students were asked to identify basketball dribbles from point-light displays. Results showed faster reaction times and greater accuracy in experts, but no advantage when observing either own or teammates’ actions compared with unknown expert players. Within an actor recognition task (Experiment 2), the same expert players were asked to identify the model actors. Results showed poor discrimination between teammates and players from another team, but a more accurate assignment of own actions to the own team. When asked to name the actor, experts recognised themselves slightly better than teammates. Results support the hypothesis that motor experience influences action recognition. They also show that the influence of motor experience on the perception of own actions depends on the type of perceptual task.     

Perceptual and decisional contributions to audiovisual interactions in the perception of apparent motion: a signal detection study

Motion information available to different sensory modalities can interact at both perceptual and post-perceptual (i.e., decisional) stages of processing. However, to date, researchers have only been able to demonstrate the influence of one of these components at any given time, hence the relationship between them remains uncertain. We addressed the interplay between the perceptual and post-perceptual components of information processing by assessing their influence on performance within the same experimental paradigm. We used signal detection theory to discriminate changes in perceptual sensitivity (d') from shifts in response criterion (c) in performance on a detection (Experiment 1) and a classification (Experiment 2) task regarding the direction of auditory apparent motion streams presented in noise. In the critical conditions, a visual motion distractor moving either leftward or rightward was presented together with the auditory motion. The results demonstrated a significant decrease in sensitivity to the direction of the auditory targets in the crossmodal conditions as compared to the unimodal baseline conditions that was independent of the relative direction of the visual distractor. In addition, we also observed significant shifts in response criterion, which were dependent on the relative direction of the distractor apparent motion. These results support the view that the perceptual and decisional components involved in audiovisual interactions in motion processing can coexist but are largely independent of one another.     

The pop out of scene-relative object movement against retinal motion due to self-movement

An object that moves is spotted almost effortlessly; it "pops out". When the observer is stationary, a moving object is uniquely identified by retinal motion. This is not so when the observer is also moving; as the eye travels through space all scene objects change position relative to the eye producing a complicated field of retinal motion. Without the unique identifier of retinal motion an object moving relative to the scene should be difficult to locate. Using a search task, we investigated this proposition. Computer-rendered objects were moved and transformed in a manner consistent with movement of the observer. Despite the complex pattern of retinal motion, objects moving relative to the scene were found to pop out. We suggest the brain uses its sensitivity to optic flow to "stabilise" the scene, allowing the scene-relative movement of an object to be identified.     

表象预期调控生物运动性别信息的识别

生物运动系在运动的生物体身的关键节点安置12～15个光点的运动痕迹形成的动画。研究表明光点生物运动包含了丰富的社会性信息,其社会性信息的识别涉及多个心理活动过程,其中大脑自上而下的知觉调控过程发挥重要作用。本研究通过两个实验探讨了表象预期在大脑自上而下调控光点生物运动性别信息识别的作用。结果发现：（1）表象预期能够加快男性生物运动的性别识别速度;想象中性形象被试倾向于将性别中立的生物运动识别为中性,而较少为男性或者女性。（2）表象预期条件和无表象预期条件下性别中立的光点生物运动性别类型识别都表现出“男性偏差”现象。（3）反应类型能够影响生物运动的性别识别。本研究有利于揭示大脑自上而下调控光点生物运动性别信息识别的心理机制。