Seeing the disappearance of unseen objects

Because of the massive amount of incoming visual information, perception is fundamentally selective. We are aware of only a small subset of our visual input at any given moment, and a great deal of activity can occur right in front of our eyes without reaching awareness. While previous work has shown that even salient visual objects can go unseen, here we demonstrate the opposite pattern, wherein observers perceive stimuli which are not physically present. In particular, we show in two motion-induced blindness experiments that unseen objects can momentarily reenter awareness when they physically disappear: in some situations, you can see the disappearance of something you can't see. Moreover, when a stimulus changes outside of awareness in this situation and then physically disappears, observers momentarily see the altered version--thus perceiving properties of an object that they had never seen before, after that object is already gone. This phenomenon of 'perceptual reentry' yields new insights into the relationship between visual memory and conscious awareness.     

Dynamic object individuation in rhesus macaques: a study of the tunnel effect

A manual-search experiment with rhesus monkeys (Macaca mulatta) explored dynamic object individuation in the tunnel effect: Subjects watched as a lemon rolled down a ramp and came to rest behind a tunnel (Occluder 1) and then as a kiwifruit emerged and became occluded at the end of its path behind a screen (Occluder 2). When the kiwifruit emerged at about the time that the lemon should have (had it continued its motion), subjects searched for food only behind Occluder 2-apparently perceiving the lemon to have transformed into a kiwifruit on the basis of spatiotemporally continuous motion. In contrast, when a brief pause interrupted the occlusion of the lemon and the emergence of the kiwifruit, monkeys searched for food behind both occluders. With further control conditions, this experiment demonstrates a spatiotemporal bias-similar to a bias found in adult visual perception-in the computation of object persistence in the context of a dynamic correspondence problem.     

Person factors associated with suicidal behavior among African American women and men

This study compared person risk factors among the following groups of low-income, African American adults in an urban, public hospital: (a) suicide attempters and nonattempters, (b) male and female attempters, and (c) all 4 groups (50 female attempters, 50 female nonattempters, 50 male attempters, and 50 male nonattempters). Participants completed psychological distress, aggression, substance use, cognitive processes, religiosity/spirituality, and ethnic identity measures. Compared with nonattempters, attempters reported more psychological distress, aggression, substance use, and maladaptive coping strategies; less religiosity/spirituality; and lower levels of ethnic identity. Male attempters endorsed more substance use than female attempters. No person risk factors differentiated among the 4 groups. Assessment of person risk factors and implementation of commensurate culturally competent interventions are recommended.     

Perceiving causality after the fact: postdiction in the temporal dynamics of causal perception

In simple dynamic events we can easily perceive not only motion, but also higher-level properties such as causality, as when we see one object collide with another. Several researchers have suggested that such causal perception is an automatic and stimulus-driven process, sensitive only to particular sorts of visual information, and a major research project has been to uncover the nature of these visual cues. Here, rather than investigating what information affects causal perception, we instead explore the temporal dynamics of when certain types of information are used. Surprisingly, we find that certain visual events can determine whether we perceive a collision in an ambiguous situation even when those events occur after the moment of potential 'impact' in the putative collision has already passed. This illustrates a type of postdictive perception: our conscious perception of the world is not an instantaneous moment-by-moment construction, but rather is formed by integrating information presented within short temporal windows, so that new information which is obtained can influence the immediate past in our conscious awareness. Such effects have been previously demonstrated for low-level motion phenomena, but the present results demonstrate that postdictive processes can influence higher-level event perception. These findings help to characterize not only the 'rules' of causal perception, but also the temporal dynamics of how and when those rules operate.     

Objects and attention: the state of the art

What are the units of attention? In addition to standard models holding that attention can select spatial regions and visual features, recent work suggests that in some cases attention can directly select discrete objects. This paper reviews the state of the art with regard to such 'object-based' attention, and explores how objects of attention relate to locations, reference frames, perceptual groups, surfaces, parts, and features. Also discussed are the dynamic aspects of objecthood, including the question of how attended objects are individuated in time, and the possibility of attending to simple dynamic motions and events. The final sections of this review generalize these issues beyond vision science, to other modalities and fields such as auditory objects of attention and the infant's 'object concept'.     

Self-reported depression in younger and older pregnant inner-city adolescents

Younger (14- to 17-year-old) inner-city adolescent mothers have been reported by Colletta (1983) as being more depressed than older (18- to 19-year-old) inner-city adolescent mothers. To determine whether this finding applies to pregnant adolescents, the revised Beck Depression Inventory (BDI; Beck, Rush, Shaw, & Emery, 1979; Beck & Steer, 1987) was administered to 175 (65.1%) Black, 64 (23.8%) Hispanic, and 30 (11.1%) White inner-city adolescents during their 28th week of pregnancy. The sample was divided into 129 (48.0%) younger (13- to 15-year-old) adolescents and 140 (52.0%) older (16- to 18-year-old) adolescents. The mean profiles of the 21 BDI symptoms were comparable for both age groups, and it was concluded that younger and older pregnant inner-city adolescents describe similar levels of self-reported depression.     

Multidimensional visual statistical learning

Recent studies of visual statistical learning (VSL) have demonstrated that statistical regularities in sequences of visual stimuli can be automatically extracted, even without intent or awareness. Despite much work on this topic, however, several fundamental questions remain about the nature of VSL. In particular, previous experiments have not explored the underlying units over which VSL operates. In a sequence of colored shapes, for example, does VSL operate over each feature dimension independently, or over multidimensional objects in which color and shape are bound together? The studies reported here demonstrate that VSL can be both object-based and feature-based, in systematic ways based on how different feature dimensions covary. For example, when each shape covaried perfectly with a particular color, VSL was object-based: Observers expressed robust VSL for colored-shape sub-sequences at test but failed when the test items consisted of monochromatic shapes or color patches. When shape and color pairs were partially decoupled during learning, however, VSL operated over features: Observers expressed robust VSL when the feature dimensions were tested separately. These results suggest that VSL is object-based, but that sensitivity to feature correlations in multidimensional sequences (possibly another form of VSL) may in turn help define what counts as an object.     

Cover-Copy-Compare and Spelling: One Versus Three Repetitions

Cover, copy, compare (CCC) has been used with success to improve spelling skills. This study adds to existing research by completing an analysis of the rewriting component of the intervention. The impact of varying the number of times a subject copied a word following an error was examined with four elementary age students. An adaptive alternating treatments design with counterbalancing was used to compare the effects of two versions of CCC and baseline during acquisition and retention 2 weeks later. During acquisition, performance in both versions of CCC was greater than that during baseline sessions. There was not an appreciable difference between versions of CCC. Retention of performance was similar for CCC1 and CCC3. Results are discussed in terms of the core components of CCC and directions for future research.     

Perceptual causality and animacy

Certain simple visual displays consisting of moving 2-D geometric shapes can give rise to percepts with high-level properties such as causality and animacy. This article reviews recent research on such phenomena, which began with the classic work of Michotte and of Heider and Simmel. The importance of such phenomena stems in part from the fact that these interpretations seem to be largely perceptual in nature - to be fairly fast, automatic, irresistible and highly stimulus driven - despite the fact that they involve impressions typically associated with higher-level cognitive processing. This research suggests that just as the visual system works to recover the physical structure of the world by inferring properties such as 3-D shape, so too does it work to recover the causal and social structure of the world by inferring properties such as causality and animacy.     

Perceptual averaging by eye and ear: Computing summary statistics from multimodal stimuli

Beyond perceiving the features of individual objects, we also have the intriguing ability to efficiently perceive average values of collections of objects across various dimensions. Over what features can perceptual averaging occur? Work to date has been limited to visual properties, but perceptual experience is intrinsically multimodal. In an initial exploration of how this process operates in multimodal environments, we explored statistical summarizing in audition (averaging pitch from a sequence of tones) and vision (averaging size from a sequence of discs), and their interaction. We observed two primary results. First, not only was auditory averaging robust, but if anything, it was more accurate than visual averaging in the present study. Second, when uncorrelated visual and auditory information were simultaneously present, observers showed little cost for averaging in either modality when they did not know until the end of each trial which average they had to report. These results illustrate that perceptual averaging can span different sensory modalities, and they also illustrate how vision and audition can both cooperate and compete for resources.