{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/110529"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/110529","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"The parallel nature of early visual processing in visual search","abstract":"Visual search is a process that is ubiquitous in daily life. Some are relatively easy – looking for a red sock among black socks – while others are extremely difficult – looking for tumors in x-ray images. Classic theories and models of search have long assumed that these easy searches, referred to as efficient search, occur in parallel and without attention and thus should not be affected by factors such as the number of items or the features of the distractors. However, there has been recent evidence that systematic variability exists even inefficient search. This led to the development of the Target Contrast Signal Theory, which proposed a different mechanism for parallel processing in visual search. In contrast to the pre-attentive process of saliency detection and generation proposed by classic theories, Target Contrast Signal Theory proposes that parallel processing in early vision involves an evidence accumulation process that is aimed at rejecting items as non-targets. In this thesis, I present a series of studies that examined the nature of the parallel process in detail. Chapter 2 examines the output of parallel processing and provides evidence in support of the mechanism described in Target Contrast Signal Theory. Chapter 3 examines the fate of the items that have been discarded in parallel processing. Lastly, Chapter 4 examines the influence of scene context on the parallel evidence accumulation process.","abstract_html":"Visual search is a process that is ubiquitous in daily life. Some are relatively easy – looking for a red sock among black socks – while others are extremely difficult – looking for tumors in x-ray images. Classic theories and models of search have long assumed that these easy searches, referred to as efficient search, occur in parallel and without attention and thus should not be affected by factors such as the number of items or the features of the distractors. However, there has been recent evidence that systematic variability exists even inefficient search. This led to the development of the Target Contrast Signal Theory, which proposed a different mechanism for parallel processing in visual search. In contrast to the pre-attentive process of saliency detection and generation proposed by classic theories, Target Contrast Signal Theory proposes that parallel processing in early vision involves an evidence accumulation process that is aimed at rejecting items as non-targets. In this thesis, I present a series of studies that examined the nature of the parallel process in detail. Chapter 2 examines the output of parallel processing and provides evidence in support of the mechanism described in Target Contrast Signal Theory. Chapter 3 examines the fate of the items that have been discarded in parallel processing. Lastly, Chapter 4 examines the influence of scene context on the parallel evidence accumulation process.","abstract_has_math":false,"creators":["Ng, Gavin JP"],"institution":"University of Illinois at Urbana-Champaign","degree_name":"Ph.D.","degree_level":"Dissertation","degree_discipline":"Psychology","degree_department":null,"school":null,"contributors":["Lleras, Alejandro","Buetti, Simona","Beck, Diane M","Christianson, Kiel","Hummel, John E"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2021,"date_issued":"2021-09-17T01:11:09Z","date_published":"2021-09-17T01:11:09Z","updated_at":"2026-07-22T22:24:52Z","subjects":["visual search","parallel processing","target contrast signal theory"],"languages":["en"],"rights":["Copyright 2021 Gavin Ng"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/2142/110529","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Lleras, Alejandro","Buetti, Simona","Beck, Diane M","Christianson, Kiel","Hummel, John E"]},{"key":"dc:creator","label":"Author","values":["Ng, Gavin JP"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2021-09-17T01:11:09Z","2021-04-23","2021-05"]},{"key":"dc:type","label":"Dc Type","values":["text","Thesis"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Psychology"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Dissertation"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Ph.D."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois at Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["visual search","parallel processing","target contrast signal theory"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2021 Gavin Ng"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["http://hdl.handle.net/2142/110529"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Visual search is a process that is ubiquitous in daily life. Some are relatively easy – looking for a red sock among black socks – while others are extremely difficult – looking for tumors in x-ray images. Classic theories and models of search have long assumed that these easy searches, referred to as efficient search, occur in parallel and without attention and thus should not be affected by factors such as the number of items or the features of the distractors. However, there has been recent evidence that systematic variability exists even inefficient search. This led to the development of the Target Contrast Signal Theory, which proposed a different mechanism for parallel processing in visual search. In contrast to the pre-attentive process of saliency detection and generation proposed by classic theories, Target Contrast Signal Theory proposes that parallel processing in early vision involves an evidence accumulation process that is aimed at rejecting items as non-targets. In this thesis, I present a series of studies that examined the nature of the parallel process in detail. Chapter 2 examines the output of parallel processing and provides evidence in support of the mechanism described in Target Contrast Signal Theory. Chapter 3 examines the fate of the items that have been discarded in parallel processing. Lastly, Chapter 4 examines the influence of scene context on the parallel evidence accumulation process.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2021-09-16 without embargo terms","The student, Gavin Ng, accepted the attached license on 2021-04-21 at 12:12.","The student, Gavin Ng, submitted this Dissertation for approval on 2021-04-21 at 12:20.","This Dissertation was approved for publication on 2021-04-23 at 10:37.","DSpace SAF Submission Ingestion Package generated from Vireo submission #16462 on 2021-09-16 at 16:45:38","Made available in DSpace on 2021-09-17T01:11:09Z (GMT). No. of bitstreams: 2 NG-DISSERTATION-2021.pdf: 1953248 bytes, checksum: a8170b4d526d0296641ae2d8901425dc (MD5) LICENSE.txt: 4205 bytes, checksum: 56f3254b8b4a69448892a7dd2e98b3b1 (MD5) Previous issue date: 2021-04-23"]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["The parallel nature of early visual processing in visual search"]}]}],"canonical_facts":{"dc:contributor":["Lleras, Alejandro","Buetti, Simona","Beck, Diane M","Christianson, Kiel","Hummel, John E"],"dc:creator":["Ng, Gavin JP"],"dc:date":["2021-09-17T01:11:09Z","2021-04-23","2021-05"],"dc:description":["Visual search is a process that is ubiquitous in daily life. Some are relatively easy – looking for a red sock among black socks – while others are extremely difficult – looking for tumors in x-ray images. Classic theories and models of search have long assumed that these easy searches, referred to as efficient search, occur in parallel and without attention and thus should not be affected by factors such as the number of items or the features of the distractors. However, there has been recent evidence that systematic variability exists even inefficient search. This led to the development of the Target Contrast Signal Theory, which proposed a different mechanism for parallel processing in visual search. In contrast to the pre-attentive process of saliency detection and generation proposed by classic theories, Target Contrast Signal Theory proposes that parallel processing in early vision involves an evidence accumulation process that is aimed at rejecting items as non-targets. In this thesis, I present a series of studies that examined the nature of the parallel process in detail. Chapter 2 examines the output of parallel processing and provides evidence in support of the mechanism described in Target Contrast Signal Theory. Chapter 3 examines the fate of the items that have been discarded in parallel processing. Lastly, Chapter 4 examines the influence of scene context on the parallel evidence accumulation process.","Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2021-09-16 without embargo terms","The student, Gavin Ng, accepted the attached license on 2021-04-21 at 12:12.","The student, Gavin Ng, submitted this Dissertation for approval on 2021-04-21 at 12:20.","This Dissertation was approved for publication on 2021-04-23 at 10:37.","DSpace SAF Submission Ingestion Package generated from Vireo submission #16462 on 2021-09-16 at 16:45:38","Made available in DSpace on 2021-09-17T01:11:09Z (GMT). No. of bitstreams: 2 NG-DISSERTATION-2021.pdf: 1953248 bytes, checksum: a8170b4d526d0296641ae2d8901425dc (MD5) LICENSE.txt: 4205 bytes, checksum: 56f3254b8b4a69448892a7dd2e98b3b1 (MD5) Previous issue date: 2021-04-23"],"dc:format":["application/pdf"],"dc:identifier":["http://hdl.handle.net/2142/110529"],"dc:language":["en"],"dc:rights":["Copyright 2021 Gavin Ng"],"dc:subject":["visual search","parallel processing","target contrast signal theory"],"dc:title":["The parallel nature of early visual processing in visual search"],"dc:type":["text","Thesis"],"thesis:degree_discipline":["Psychology"],"thesis:degree_level":["Dissertation"],"thesis:degree_name":["Ph.D."],"thesis:institution_name":["University of Illinois at Urbana-Champaign"]},"updated_at":"2026-07-22T22:24:52Z"}