Assessing the public health risk of microbial intrusion events in distribution systems: conceptual model, available data, and challenges

Low and negative pressure events in drinking water distribution systems have the potential to result in intrusion of pathogenic microorganisms if an external source of contamination is present (e.g., nearby leaking sewer main) and there is a pathway for contaminant entry (e.g., leaks in drinking water main). While the public health risk associated with such events is not well understood, quantitative microbial risk assessment can be used to estimate such risk. A conceptual model is provided and the state of knowledge, current assumptions, and challenges associated with the conceptual model parameters are presented. This review provides a characterization of the causes, magnitudes, durations and frequencies of low/negative pressure events; pathways for pathogen entry; pathogen occurrence in external sources of contamination; volumes of water that may enter through the different pathways; fate and transport of pathogens from the pathways of entry to customer taps; pathogen exposure to populations consuming the drinking water; and risk associated with pathogen exposure.     

On the joint effects of stimulus quality, regularity, and lexicality when reading aloud: New challenges.

A number of computational models have been developed over the last 2 decades that are remarkably successful at explaining the process of translating print into sound. Nevertheless, 2 of the most successful computational accounts on the table fail to simulate the results from factorial experiments reported in this article in which university students read aloud letter strings that varied in terms of spelling–sound regularity and lexicality (regular words vs. exception words vs. nonwords) and stimulus quality (bright vs. dim). Skilled readers yielded additive effects of regularity and stimulus quality and additive effects of lexicality and stimulus quality on both RT and errors when nonwords were mixed with words. When only words appeared in the list, there was an interaction in which exception words were less affected by low stimulus quality than regular words were; no existing account anticipates or explains these results. We advance a hypothesis that assumes a novel module that accommodates these data and provide an existence proof in the form of a simulation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Basic processes in reading: Can functional phonological recoding be blocked?

A widely held view is that phonological processing is always involved in lexical access from print, and is automatic in that it cannot be prevented. This claim was assessed in the context of a priming paradigm. In Experiment 1, repetition priming was observed for both pseudohomophone-word pairs (e.g., brane-brain) and morphologically related word pairs (e.g., marked-mark) in the context of lexical decision. In Experiment 2, subjects searched the prime for the presence of a target letter and then made a lexical decision to a subsequent letter string. Phonological priming from a pseudohomophone was eliminated following letter search of the prime, whereas morphological priming persisted. These results are inconsistent with the claim that a) lexical access from print requires preliminary phonological processing, and b) functional phonological processing cannot be blocked. They are, however, consistent with the conclusion that, for intact skilled readers, lexical access can be accomplished on the basis of orthographic processing alone. These results join a growing body of evidence supporting the claim that there exist numerous points in visual word recognition at which processing can be stopped. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Neighborhood effects in reading aloud: New findings and new challenges for computational models.

A word from a dense neighborhood is often read aloud faster than a word from a sparse neighborhood. This advantage is usually attributed to orthography, but orthographic and phonological neighbors are typically confounded. Two experiments investigated the effect of neighborhood density on reading aloud when phonological density was varied while orthographic density was held constant, and vice versa. A phonological neighborhood effect was observed, but not an orthographic one. These results are inconsistent with the predominant role ascribed to orthographic neighbors in accounts of visual word recognition and reading aloud. Consistent with this interpretation, 6 different computational models of reading aloud failed to simulate this pattern of results. The results of the present experiments thus provide a new understanding of some of the processes underlying reading aloud, and new challenges for computational models. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Deep dyslexia and the right hemisphere hypothesis: Evidence from the U.S.A. and the U.S.S.R.

Discusses the theory that asserts that the residual reading abilities seen in deep dyslexia entirely reflect the operation of an intact right hemisphere reading system rather than a partially disabled left hemisphere reading system. Evidence from an experiment with normal Ss in a report by the present author and colleagues (1983) is presented, which suggests that the right hemisphere contains no lexical entries for abbreviations that can be accessed by visual presentation. Data are presented from studies by K. E. Patterson (1980; see also PA, Vols 63:12203 and 64:10691) on 2 male deep dyslexic's understanding of printed abbreviations, along with observations of a young female deep dyslexic who was tested on understanding of abbreviations and on letter-naming abilities. Considerable sparing of the ability to obtain semantic information from printed abbreviations was evidenced in all 3 Ss. This contrast suggests that the current right hemisphere account of the residual reading abilities seen in deep dyslexia is not a sufficient one and should be modified. (French abstract) (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reading pseudohomophones: Implications for models of pronunciation assembly and the locus of word-frequency effects in naming.

Pronunciation performance under speeded conditions was examined for various kinds of letter strings, including pseudohomophones (e.g., TRAX), their real word counterparts (e.g., TRACKS), and a set of nonword controls (e.g., PRAX). Experiment 1 yielded a pronunciation advantage for the pseudohomophones relative to the controls, which was largest among items having few or no orthographic neighbors. Experiment 2 ruled out an account of the pseudohomophone advantage based on differences between pseudohomophones and controls in initial phonemes. Experiment 3 established the existence of a large frequency effect on pronunciation of the base words themselves. These results suggest that whole word representations in the phonological output lexicon are consulted in the course of assembling a pronunciation and that representations in a phonological output lexicon are insensitive to word frequency. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reading aloud: Qualitative differences in the relation between stimulus quality and word frequency as a function of context.

Virtually all theories of visual word recognition assume (typically implicitly) that when a pathway is used, processing within that pathway always unfolds in the same way. This view is challenged by the observation that simple variations in list composition are associated with qualitative changes in performance. The present experiments demonstrate that when reading aloud, the joint effects of stimulus quality and word frequency on response time are driven by the presence/absence of nonwords in the list. Interacting effects of these factors are seen when only words appear in the experiment, whereas additive effects are seen when words and nonwords are randomly intermixed. One way to explain these and other data appeals to the distinction between cascaded processing (or interactive activation) on the one hand versus a thresholded mode of processing on the other, with contextual factors determining which mode of processing dominates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Contextual effects on reading aloud: Evidence for pathway control.

Recent evidence suggests that the processes responsible for generating a phonological code from print are flexible in skilled readers. An important goal, therefore, is to identify the conditions that lead to changes in how a phonological code is computed. Five experiments are reported that examine whether phonological processes change as predicted by the pathway control hypothesis when reading aloud words and nonwords. Changes in reading processes were assessed by measuring the effect of predictable switches between stimulus categories across trials. The results of the present experiments are argued to be consistent with the pathway control hypothesis. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Models of visual word recognition: When obscuring the stimulus yields a clearer view.

It is well known that visual word recognition is influenced by context, word frequency, and stimulus quality. A processing account is outlined in which stimulus quality affects the orthographic input lexicon, whereas context influences both the orthographic input lexicon and the semantic system. Word frequency exerts its primary effects on the pathways that link lexical systems with each other and with the semantic system. Previous findings that are problematic for alternative models along with the results of 2 new experiments are consistent with this account. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The process of lexical decision: More words about a parallel distributed processing model.

Central to M. S. Seidenberg and J. L. McClelland's (1989) parallel distributed processing model's account of lexical decision is the assumption that performance is determined by the amount of overlap in the distribution of the orthographic error scores between words and nonwords. The present experiment demonstrates lexical decision performance that is independent of the distribution of orthographic error scores between words and nonwords. Furthermore, the orthographic error scores from the model capture no variance in the reaction time (RT) data to words, even in a condition in which the orthographic overlap between words and nonwords is minimal. Other issues are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)