Joseph S. Brown

Visual masking and visual integration across saccadic eye movements.

The visual world appears unified, stable, and continuous despite rapid changes in eye position. How this is accomplished has puzzled psychologists for over a century. One possibility is that visual information from successive eye fixations is fused in memory according to environmental or spatiotopic coordinates. Evidence supporting this hypothesis was provided by Davidson, Fox, and Dick (1973). They presented a letter array in one fixation and a mask at one letter position in a subsequent fixation and found that the mask inhibited report of the letter that shared its retinal coordinates but appeared to occupy the same position as the letter that shared its spatial coordinates. This suggests the existence of a retinotopic visual persistence at which transsaccadic masking occurs and a spatiotopic visual persistence at which transsaccadic integration, or fusion, occurs. Using a similar procedure, we found retinotopic masking and retinotopic integration: The mask interfered with the letter that shared its retinal coordinates, but also appeared to cover that letter. In another experiment, instead of a mask we presented a bar marker over one letter position, and subjects reported the letter that appeared underneath the bar; subjects usually reported the letter with the same retinal coordinates as the bar, again suggesting retinotopic rather than spatiotopic integration across saccades. In Experiment 3 a bar marker was again presented over one letter position, but in addition a visual landmark was presented after the saccade so that subjects could localize the bars spatial position; subjects still reported that the letter that shared the bars retinal coordinates appeared to be under it, but they were also able to accurately specify the bars spatial position. This ability could have been based on retinal information (the visual landmark) present in the second fixation only, however, rather than spatiotopic visual persistence. Because such a visual landmark was present in the Davidson et al. (1973) experiments, we conclude that their findings can be explained solely in retinotopic terms and provide no convincing evidence for spatiotopic visual persistence. But the exposure parameters that Davidson et al. (1973) and we used were biased in favor of retinotopic, rather than spatiotopic, coding: The stimuli were presented very briefly just before a saccadic eye movement, and subjects are poor at spatially localizing stimuli under these conditions. Thus, in Experiment 4 we presented the letter array about 200 ms before the saccade; then, subjects reported that the letter with the same spatial coordinates as the bar appeared under it.(ABSTRACT TRUNCATED AT 400 WORDS)

Visual memory and the perception of a stable visual environment

The visual world appears stable and continuous despite eye movementa. One hypothesisabout how this perception is achieved is that the contents of succesaivatienn~arefusedinmemory according to environmental coordinates. Two experiments failed to support this hypothesis; they showed that one’s ability to detecta grating presented after a saccade is unaffected by the presentation of a grating with the same spatial frequency in the same spatial location before the saccade. A third experiment tested an alternative explanation of perceptual stability that claims that the contents of successive fixations are compared, rather than fused, across-saccades, allowing one to determine whether the world has remained stable. This hypothesis was supported: Experienced subjects could accurately determine whether two patterns viewed in successive fixationswere identical or different, evenwhenthe two patterns appeared in different spatial positions across the saccade. Taken together, these results suggest that perceptual stability and information integration across saccades rely on memory for the relative positions of objects in the environment, rather than on the spatiotopic fusion of visual information from successive fixations.

Limits on perceptual abstraction in reading: Asymmetric transfer between surface forms differing in typicality.

In 2 experiments and a rating study we examined asymmetric transfer of repetition benefit between two easily readable surface forms. Typed second occurrences showed benefit that was similar for words and pseudowords and did not depend on the surface form of the first occurrence. Handwritten second occurrences showed benefit only for words, and benefit was larger when first occurrences were handwritten than when typed. This pattern, which was unrelated to explicit memory, characterized both naming and lexical decision, and benefit transferred between tasks. These results tax current episodic accounts of repetition benefit that are based on retrieving perceptual records or conceptual interpretations, and they tax strongly abstractionist accounts that are based on extremely general visual analysis

The dissociation of repetition priming and recognition memory in language/learning-disabled children

Recent research has found that the performance of learning-disabled and non-disabled children is dissociated on explicit and implicit tests of memory (Lorsbach & Worman, 1989). The current study further examined this phenomenon by comparing language/learning-disabled (L/LD) and nondisabled children (NLD) on tasks measuring primed picture-naming and item recognition. Included within the design of the experiment was the manipulation of both presentation format (pictures or words) and retention interval (immediate or 1 day). Children were initially presented with pictures and words. Performance was measured both immediately and following a 1-day retention interval on a picture naming task, an item recognition task, and a supplementary measure of memory for presentation format. The magnitude of facilitation associated with primed picture-naming was found to be independent of item recognition performance. In addition, the effects of population (L/LD and NLD) and retention interval (immediate test or 1 day) each produced dissociations between the magnitude of naming facilitation and item recognition performance. Results were discussed in terms of their implications for our understanding of the nature of memory difficulties in L/LD children.

Orthographically Mediated Inhibition Effects: Evidence of Activational Feedback During Visual Word Recognition

Models of visual word recognition that have adopted an interactive activation framework (e.g., Coltheart, Curtis, Atkins, & Haller, 1993; Grainger & Jacobs, 1996) assume that activation can spread from semantic to orthographic representations via a feedback mechanism during visual word recognition. The present study used a mediated priming paradigm to test whether such feedback exists and, if so, under what conditions. Participants named aloud targets that were preceded either by a semantically related prime (e.g.,dog-cat) or by a prime that was related to the target via a mediating word (e.g., cat-g-bog). Direct evidence of activational feedback was obtained in the form of orthographically mediated inhibition effects. These mediated inhibition effects are consistent with activational feedback and support models of visual word recognition that have adopted an interactive activation framework.

“You Don't Know Me, But …”: Access to Patient Data and Subject Recruitment in Human Subjects Research

Recruiting subjects to participate in a research study is the first step in the consent process, and therefore falls within the purview of the institutional review board (IRB) (Huntington and Robinson 2007; Neff 2008). It is a common practice to screen patients’ medical information to ensure that recruitment efforts are targeted to the appropriate individuals, a practice permitted under the Heath Insurance and Portability and Accountability Act (HIPAA) preparatory research provision (U.S. Department of Health and Human Services 2003). However, this practice raises some privacy concerns. There is a clear tension here, between the needs of investigators to recruit subjects sufficient to the conduct of scientifically valid research (Ness 2007; Sataloff 2008; Wolf 2006) and the rights of patients to have their information protected. Issues of patient privacy in screening and recruitment apply regardless of the regulatory framework. The Council for International Organizations of Medical Sciences (CIOMS) International Ethical Guidelines for Biomedical Research Involving Human Subjects, for example, describe the sanctioned use of epidemiological and other data without obtaining informed consent (p. 75). Yet we have chosen to frame our discussion within the scope of research practices and regulations in the United States for two reasons. First, the U.S. system is so large that small risks are magnified by sheer repetition. Second, the U.S. regulatory system (and HIPPA especially) has several particular shortcomings that illustrate our general concerns. In this article, we argue that maintaining a patient’s right to privacy is an essential factor in determining who has le-