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Reanalysis of single-letter identification data across letter sizes near the resolution threshold used 10 Sloan letters at central and paracentral field locations. Observers displayed stable letter-specific biases that affected over- and under-calling. Using signal detection theory, a noisy template model separated bias from sensitivity differences and fit bias-varying templates substantially better. Effects predicted by additive template bias suggested small impacts on most settings.",{"@graph":63,"@context":118},[64,80,101],{"@type":65,"itemListElement":66},"BreadcrumbList",[67,71,74,77],{"item":68,"name":69,"@type":70,"position":9},"https://docshare.wps.com","Home","ListItem",{"item":72,"name":10,"@type":70,"position":73},"https://docshare.wps.com/template/",2,{"item":75,"name":51,"@type":70,"position":76},"https://docshare.wps.com/template/general/",3,{"item":78,"name":59,"@type":70,"position":79},"https://docshare.wps.com/template/revealing-the-influence-of-bias-in-a-letter-acuity-identification-task-a-noisy-template-model/280906/",4,{"url":78,"name":59,"@type":81,"image":82,"author":87,"headline":59,"publisher":90,"fileFormat":93,"inLanguage":57,"description":61,"dateModified":94,"datePublished":95,"encodingFormat":93,"isAccessibleForFree":96,"interactionStatistic":97},"DigitalDocument",{"url":83,"@type":84,"width":85,"height":86},"https://docshare.wps.com/thumbnails/revealing-the-influence-of-bias-in-a-letter-acuity-identification-task-a-noisy-template-model/280906.png","ImageObject",442,249,{"name":88,"@type":89},"Tawan","Person",{"url":68,"name":91,"@type":92},"DocShare","Organization","application/pdf","2026-09-21","2026-09-16",true,{"@type":98,"interactionType":99,"userInteractionCount":9},"InteractionCounter",{"@type":100},"ViewAction",{"@type":102,"mainEntity":103},"FAQPage",[104,110,114],{"name":105,"@type":106,"acceptedAnswer":107},"What was the study testing in clinical letter acuity tasks?","Question",{"text":108,"@type":109},"The study tested whether observers’ performance in letter acuity identification tasks reflects only sensory ability or whether systematic letter biases also influence results.","Answer",{"name":111,"@type":106,"acceptedAnswer":112},"How did the researchers analyze letter identification data?",{"text":113,"@type":109},"They reanalyzed single-letter identification outcomes across letter sizes spanning the resolution threshold, using 10 Sloan letters at different visual field locations.",{"name":115,"@type":106,"acceptedAnswer":116},"What model was proposed to separate bias from sensitivity?",{"text":117,"@type":109},"The authors developed a noisy template model within the framework of signal detection theory to distinguish bias effects from sensitivity variations across letter templates.","https://schema.org",{"og:url":78,"og:type":120,"og:title":59,"og:site_name":91,"og:description":61},"article",{"robots":122,"canonical":78},"index,follow",{"doc_id":124,"site_id":56},280906,1789958817,{"code":4,"msg":5,"data":127},{"doc_id":124,"user_id":128,"nickname":88,"user_avatar":129,"doc_module":9,"category_id":50,"category_name":51,"doc_title":59,"doc_description":61,"doc_content":130,"file_id":131,"file_url":132,"file_type":133,"file_size":134,"view_count":9,"is_deleted":4,"is_public":9,"is_downloadable":9,"audit_status":9,"page_count":20,"language":135,"language_code":57,"site_id":56,"html_lang":57,"table_of_contents":136,"faqs":137,"seo_title":138,"seo_description":61,"update_tm":139,"read_time":47},2336475104042,"https://ap-avatar.wpscdn.com/avatar/22000c4c32af1715be0?x-image-process=image/resize,m_fixed,w_180,h_180&k=1786537525561427321","Vision Research 208 (2023) 108233  \nContents lists available at ScienceDirect  \nVision Research  \njournal [homepage:](homepage: www.elsevier.com/locate/visres)[ www.elsevier.com/locate/visres](homepage: www.elsevier.com/locate/visres)  \n| Revealing the influence of bias in a letter acuity identification task: A noisy   template model\u003Cbr>Mark A. Georgeson a, b, *, Hatem Barhoomb, c, Mahesh R. Joshib, Paul H. Artesb, Gunnar Schmidtmann b\u003Cbr>a School of Life & Health Sciences, Aston University, B4 7ET, UK\u003Cbr>b Eye & Vision Research Group, School of Health Professions, University of Plymouth, PL4 8AA, UK c Islamic University of Gaza, P.O. Box 108, Gaza, Palestine |  |  |\n| --- | --- | --- |\n| A R T I C L E I N F O |  | A B S T R A C T |\n| Keywords:\u003Cbr>Visual acuity\u003Cbr>Letter recognition Bias\u003Cbr>Noisy template model Sloan letters |  | In clinical testing of visual acuity, it is often assumed that performance reflects sensory abilities and observers do not exhibit strong biases for or against specific letters, but this assumption has not been extensively tested. We reanalyzed single-letter identification data as a function of letter size, spanning the resolution threshold, for 10 Sloan letters at central and paracentral visual field locations. Individual observers showed consistent letter biases across letter sizes. Preferred letters were named much more often and others less often than expected (group averages ranged from 4% to 20% across letters, where the unbiased rate was 10%). In the framework of signal detection theory, we devised a noisy template model to distinguish biases from differences in sensitivity. When bias varied across letter templates the model fitted very well-much better than when sensitivity varied without bias. The best model combined both, having substantial biases and small variations in sensitivity across letters. The over- and under-calling decreased at larger letter sizes, but this was well-predicted by template responses that had the same additive bias for all letter sizes: with stronger inputs (larger letters) there was less opportunity for bias to influence which template gave the biggest response. The neural basis for such letter bias is not known, but a plausible candidate is the letter-recognition machinery of the left temporal lobe. Future work could assess whether such biases affect clinical measures of visual performance. Our analyses so far suggest very small effects in most settings. |\n\n1. Introduction  \nObservers in sensory and perceptual tasks typically make decisions about the presence, absence or identity of target stimuli presented under conditions of uncertainty. The aim of such experiments is often to characterize the limits of performance of a human sensory system, such as vision or hearing, by finding the weakest, quietest or smallest stimulus that can still be reliably detected, or the smallest difference between two similar stimuli that can be reliably resolved. In optometric practice, clinicians routinely measure visual acuity, i.e. the ability of a patient to discriminate the smallest details of a stimulus (optotype). Thus, the assessment of vision in clinical optometry is essentially a psychophysical experiment. The conceptual framework for psychophysical experiments of this kind was revolutionized in the 1950s and early 1960s by the application of Signal Detection Theory (SDT) to the interpretation of human sensory performance (Green & Swets, 1966; Swets, 1961; Swets,  \nTanner, & Birdsall, 1961; Tanner, 1956; Tanner & Swets, 1954). One of SDT’s lasting contributions was to enable a formal distinction between two key components of performance-sensitivity and bias. Despite this conceptual revolution, SDT has not often been used explicitly to interpret letter acuity performance, or to examine the role of bias in clinical letter acuity measurements. In this paper, we apply SDT using a fairly simple template model for letter recognition, and we quantify the degree of bias shown by ind","cbCaic0BddYptgbr","https://ap.wps.com/l/cbCaic0BddYptgbr","pdf",1429345,"English","# Introduction\n## Signal detection theory and psychophysical performance\n## Bias in letter identification and clinical acuity measurements\n## Template model approach","[{\"question\":\"What was the study testing in clinical letter acuity tasks?\",\"answer\":\"The study tested whether observers’ performance in letter acuity identification tasks reflects only sensory ability or whether systematic letter biases also influence results.\"},{\"question\":\"How did the researchers analyze letter identification data?\",\"answer\":\"They reanalyzed single-letter identification outcomes across letter sizes spanning the resolution threshold, using 10 Sloan letters at different visual field locations.\"},{\"question\":\"What model was proposed to separate bias from sensitivity?\",\"answer\":\"The authors developed a noisy template model within the framework of signal detection theory to distinguish bias effects from sensitivity variations across letter templates.\"}]","Revealing the influence of bias in a letter acuity identification task - A noisy template model | PDF",1789562005]