{"id":6021,"date":"2026-10-19T09:48:23","date_gmt":"2026-10-19T09:48:23","guid":{"rendered":"https:\/\/phd.hi.is\/doktorsvorn\/doktorsvorn-i-salfraedi-tomas-kristjansson\/"},"modified":"2026-10-19T09:48:23","modified_gmt":"2026-10-19T09:48:23","slug":"doktorsvorn-i-salfraedi-tomas-kristjansson","status":"publish","type":"phd_defence","link":"https:\/\/phd.hi.is\/en\/doktorsvorn\/doktorsvorn-i-salfraedi-tomas-kristjansson\/","title":{"rendered":"Doktorsv\u00f6rn \u00ed S\u00e1lfr\u00e6\u00f0i – T\u00f3mas Kristj\u00e1nsson"},"content":{"rendered":"
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Fimmtudaginn 27. september ver T\u00f3mas Kristj\u00e1nsson doktorsritger\u00f0 s\u00edna \u00ed s\u00e1lfr\u00e6\u00f0i vi\u00f0 S\u00e1lfr\u00e6\u00f0ideild H\u00e1sk\u00f3la \u00cdslands. Ritger\u00f0in ber heiti\u00f0: Ranns\u00f3knir \u00e1 sj\u00f3nr\u00e6nni athygli me\u00f0 s\u00f6fnunarverkefnum. Dynamics and flexibility of visual attention -Insights from a foraging perspective.<\/strong><\/p>\n

Andm\u00e6lendur eru dr. Jeremy M. Wolfe, ranns\u00f3knapr\u00f3fessor vi\u00f0 Harvard Medical School, og dr. \u00de\u00f3r Eysteinsson, pr\u00f3fessor vi\u00f0 L\u00e6knadeild H\u00e1sk\u00f3la \u00cdslands.<\/p>\n

Umsj\u00f3narkennari og lei\u00f0beinandi var \u00c1rni Kristj\u00e1nsson, pr\u00f3fessor vi\u00f0 S\u00e1lfr\u00e6\u00f0ideild H\u00e1sk\u00f3la \u00cdslands. Auk hans sat \u00ed doktorsnefnd dr. Ian M. Thornton, pr\u00f3fessor vi\u00f0 University of Malta.<\/p>\n

Dan\u00edel \u00de\u00f3r \u00d3lason, deildarforseti S\u00e1lfr\u00e6\u00f0ideildar, stj\u00f3rnar ath\u00f6fninni sem fer fram \u00ed H\u00e1t\u00ed\u00f0asal H\u00e1sk\u00f3la \u00cdslands og hefst kl. 13.00.<\/p>\n

\u00c1grip af ranns\u00f3kn<\/strong><\/p>\n

Sj\u00f3nin og sj\u00f3nkerfi\u00f0 hafa veri\u00f0 hug\u00f0arefni heimspekinga og v\u00edsindamanna um aldir. S\u00e1lfr\u00e6\u00f0ingar hafa rannsaka\u00f0 \u00fdmsa \u00fe\u00e6tti sj\u00f3nar og skynjunar s\u00ed\u00f0an tilraunas\u00e1lfr\u00e6\u00f0i var\u00f0 til. Ein undirgrein sj\u00f3nv\u00edsinda eru athyglis- og sj\u00f3nleitarranns\u00f3knir. S\u00fa undirgrein rannsakar hvernig athygliskerfi og -ferlar gera okkur kleift a\u00f0 finna og vinna \u00far mark\u00e1reitum sem vi\u00f0 leitum a\u00f0. \u00deetta hefur veri\u00f0 rannsaka\u00f0 \u00edtarlega me\u00f0 eins-mark\u00e1reitis ranns\u00f3knum \u00fear sem leita\u00f0 er a\u00f0 einu mark\u00e1reiti innan um marga truflara. \u00deetta hefur veri\u00f0 mj\u00f6g gj\u00f6fult ranns\u00f3knasvi\u00f0 og margir athyglisferlar og \u00e1hrif hafa fundist vegna \u00feeirra. Flest athyglisl\u00edk\u00f6n byggjast \u00e1 ni\u00f0urst\u00f6\u00f0um eins \u00e1reitis ranns\u00f3kna og \u00feessi l\u00edk\u00f6n hafa auki\u00f0 skilning okkar og \u00feekkingu \u00e1 sj\u00f3nskynjun margfalt. Sj\u00f3nver\u00f6ld okkar er hins vegar oft fl\u00f3knari og breytilegri en a\u00f0 leita a\u00f0 st\u00f6ku kyrrst\u00e6\u00f0u mark\u00e1reiti innan um nokkra truflara. \u00cd \u00fdmsum n\u00e1tt\u00farulegum a\u00f0st\u00e6\u00f0um leitum vi\u00f0 a\u00f0 m\u00f6rgum \u00e1reitum \u00e1 sama t\u00edma, eins og \u00feegar vi\u00f0 erum vi\u00f0 berjat\u00ednslu e\u00f0a a\u00f0 finna r\u00e9tta skiptimynt \u00ed matv\u00f6ruverslun. Innan sj\u00f3nv\u00edsinda er \u00feetta kalla\u00f0 s\u00f6fnun. S\u00f6fnun hefur a\u00f0allega veri\u00f0 ranns\u00f6ku\u00f0 hj\u00e1 d\u00fdrum og \u00e1 \u00fear vi\u00f0 um f\u00e6\u00f0us\u00f6fnun d\u00fdra. Nokkurt misr\u00e6mi er milli skilgreininga \u00e1 s\u00f6fnun innan sj\u00f3nv\u00edsinda en \u00fea\u00f0 sem \u00fe\u00e6r eiga sameiginlegt er a\u00f0 s\u00f6fnun \u00e1 vi\u00f0 um m\u00f6rg mark\u00e1reiti \u00e1 sama t\u00edma. \u00cd ranns\u00f3kninni var nota\u00f0 n\u00fdst\u00e1rlegt iPad s\u00f6fnunarverkefni, \u00fear sem \u00fe\u00e1tttakendur snertu \u00f6ll \u00e1reiti af fyrirfram \u00e1kve\u00f0num lit og\/e\u00f0a l\u00f6gun og hunsu\u00f0u \u00f6nnur. M\u00e6ldur var milli-\u00e1reitist\u00edmi \u00ed gegnum s\u00f6fnunarferli\u00f0 og borinn saman milli-\u00e1reitis t\u00edmi eftir \u00fev\u00ed hvort snert var \u00e1reiti \u00far sama e\u00f0a \u00f3l\u00edkum \u00e1reitisflokki og hi\u00f0 s\u00ed\u00f0asta. \u00dear a\u00f0 auki var greint s\u00f6fnunarmynstur me\u00f0 \u00fev\u00ed a\u00f0 greina fj\u00f6lda runa, \u00fear sem hver runa skilgreinist sem \u00f6ll \u00e1reiti sem safna\u00f0 er \u00e1\u00f0ur en skipt er um \u00e1reitisflokk. Kynntar eru \u00ferj\u00e1r greinar \u00fear sem fj\u00f6lda \u00e1reita, hlutfalli mark\u00e1reita, t\u00edmam\u00f6rkum og fj\u00f6lda \u00e1reitisflokka er stj\u00f3rna\u00f0. Ni\u00f0urst\u00f6\u00f0urnar s\u00fdna \u00edtarlega og \u00e1hugaver\u00f0a mynd af s\u00f6fnunarferlinu. Greint er fr\u00e1 \u00feremur a\u00f0skildum stigum s\u00f6fnunarferlisins. Fyrsta stigi\u00f0 er st\u00f6\u00f0uga stigi\u00f0, sem inniheldur \u00f6ll \u00e1reitin nema hi\u00f0 s\u00ed\u00f0asta og \u00e1reiti\u00f0 fyrir mi\u00f0ju s\u00f6fnunarferlisins. \u00c1 st\u00f6\u00f0uga stiginu eru milli-\u00e1reitat\u00edmarnir st\u00f6\u00f0ugir og \u00f6rl\u00edti\u00f0 h\u00e6gist \u00e1 \u00feeim \u00ed gegnum s\u00f6fnunarferli\u00f0. L\u00edtill sem enginn munur er \u00e1 st\u00f6\u00f0uga stiginu \u00e1 milli \u00fe\u00e1tta og sams\u00f6fnunar sem passar illa vi\u00f0 tveggja stiga kenningar um sj\u00f3nr\u00e6na athygli. Anna\u00f0 stigi\u00f0 er mi\u00f0risi\u00f0, \u00fea\u00f0 kemur a\u00f0eins fram \u00ed sams\u00f6fnun og sk\u00fdrist af skiptingu \u00e1 milli mark\u00e1reitisflokka. Flestir \u00fe\u00e1tttakendur gera \u00fea\u00f0 a\u00f0eins einu sinni \u00ed sams\u00f6fnun. Mi\u00f0risi\u00f0 kemur fram sem ris \u00ed milli-\u00e1reitist\u00edma \u00ed mi\u00f0ri s\u00f6fnunarlotunni. S\u00ed\u00f0asta stigi\u00f0 er endarisi\u00f0 sem einnig einkennist af risi \u00ed milli-\u00e1reitist\u00edma, en a\u00f0eins fyrir s\u00ed\u00f0asta mark\u00e1reiti\u00f0 \u00ed hverri s\u00f6fnunarlotu. \u00deetta stig kemur b\u00e6\u00f0i fram \u00ed \u00fe\u00e1tta- og sams\u00f6fnunarverkefnum en er mun st\u00e6rra \u00ed sams\u00f6fnun en \u00fe\u00e1ttas\u00f6fnun. Endurtekin eru \u00feekkt mynstur \u00fear sem \u00fe\u00e1tttakendur skipta tilviljanakennt \u00e1 milli mark\u00e1reitisflokka \u00ed \u00fe\u00e1ttas\u00f6fnun en kl\u00e1ra sams\u00f6fnunarlotur \u00ed tveimur l\u00f6ngum runum. \u00dea\u00f0 breytist hins vegar \u00feegar sett eru t\u00edmam\u00f6rk \u00e1 verkefni\u00f0, \u00fe\u00e1 skipta \u00fe\u00e1tttakendur oftar \u00e1 milli mark\u00e1reitisflokka, eftir \u00fev\u00ed sem t\u00edmam\u00f6rkin eru styttri. \u00deetta s\u00fdnir a\u00f0 s\u00f6fnunarmynstrin gefa ekki endilega til kynna takmarkanir e\u00f0a vangetu sj\u00f3nr\u00e6na athygliskerfisins, heldur s\u00fdnir \u00feetta frekar hversu sveigjanlegt kerfi\u00f0 er og mikilv\u00e6gi \u00e1kvar\u00f0ana \u00fe\u00e1tttakenda sem geta or\u00f0i\u00f0 fyrir \u00f3afvitandi \u00e1hrifum fr\u00e1 skilyr\u00f0um verkefnisins frekar en athygliskerfisins. A\u00f0 lokum fann rannsakandi stu\u00f0ning fyrir hle\u00f0slukenningum um sj\u00f3nr\u00e6nt vinnsluminni \u00fear sem gert er r\u00e1\u00f0 fyrir a\u00f0 fleiri en eitt leitarsni\u00f0m\u00e1t geti veri\u00f0 virkt \u00e1 sama t\u00edma. Ni\u00f0urst\u00f6\u00f0urnar passa illa vi\u00f0 einf\u00f6ld tveggja stiga l\u00edk\u00f6n af sj\u00f3nr\u00e6nni athygli og sty\u00f0ja mun sveigjanlegri s\u00fdn \u00e1 sj\u00f3nr\u00e6na athygli.<\/p>\n

Abstract<\/strong><\/p>\n

Vision and its properties has interested philosophers and scientists alike for centuries. Psychologists have studied vision and perception since the inception of experimental psychology. One subfield of vision science is the study of visual attention and more specifically visual search. This subfield studies how attentional mechanisms enable us to identify and process targets that we are searching for. This has extensively been studied with observers searching for a single target amongst number of distractors. This has been a very fruitful avenue of research and many mechanisms have been discovered through this line of research. Most models of visual attention are based on these findings and these models have greatly increased our understanding of the visual and perceptual system. Our visual world is however often more complex and dynamic than involving a single static target among a number of distractors. In several natural situations, we search for multiple targets instead, like when we are picking berries or selecting coins to pay for your groceries. Within vision science, this is referred to as foraging. Foraging originates from the animal literature and there refers to the animals foraging for food and although there are discrepancies within the visual science literature between definitions, they all involve searching for multiple targets. Using a novel iPad foraging task, where participants tap on all targets of pre-designated colours and\/or shapes while ignoring distractors of different colours and\/or shapes, I measured the inter-target times throughout the foraging process, compared inter-target times between taps after switching between target categories and when taps were repeated within target category. In addition, I analysed foraging strategies by analysing the number of runs where a run refers to the repeated selection within the same target category. This thesis consists of three papers, where absolute set-size, relative set-size, time limits and the number of target categories are manipulated. The results reveal an intriguing and detailed picture of the foraging process. I identify three distinct phases of the foraging process. A cruise phase which includes all targets except the middle one and the last one. During the cruise phase the inter-target times remain stable with a slight slowing throughout the foraging process. Interestingly, there is little or no difference between the cruise phase for feature and conjunction foraging which does not fit well with two-stage models of visual attention. The second phase is the middle peak, the middle peak only appears in conjunction foraging and represents the switch between target categories which for most observers only happens once in conjunction foraging, it can be seen by a peak in the intertarget times in the middle of the conjunction foraging trial. The last phase is the end-peak which is also a peak in the inter-target times, but for the last target. This peak is apparent in both feature and conjunction foraging but is many times larger in conjunction foraging than feature foraging. I replicate a known pattern where observers switch randomly between target categories in feature foraging but complete the conjunction foraging task in two long runs. However, when imposing time limits on the foraging, participants switch more frequently, the shorter the time limit is. This shows that these foraging patterns are not indicative of limitations of or inability of the visual attentional system, but rather shows the great flexibility of the system and the importance of strategy that can be affected by task demands. Lastly, I found support for load theories of visual working memory that state that more than one search template can be active simultaneously. Taken together, the results do not fit well with simple two-stage models of visual attention and support a much more flexible view of visual attention.<\/p>\n

Um doktorsefni\u00f0<\/strong><\/p>\n

T\u00f3mas Kristj\u00e1nsson er f\u00e6ddur \u00e1ri\u00f0 1984. Foreldrar hans eru Valger\u00f0ur T\u00f3masd\u00f3ttir og Gr\u00e9tar Ingi S\u00edmonarson. T\u00f3mas er tr\u00falofa\u00f0ur Kristj\u00f6nu Kristinsd\u00f3ttur s\u00e1lfr\u00e6\u00f0ingi.<\/p>\n

T\u00f3mas lauk B.Sc pr\u00f3fi \u00ed s\u00e1lfr\u00e6\u00f0i fr\u00e1 H\u00e1sk\u00f3la \u00cdslands \u00e1ri\u00f0 2013 og hlaut cand.psych. gr\u00e1\u00f0u \u00ed s\u00e1lfr\u00e6\u00f0i og starfstitilinn s\u00e1lfr\u00e6\u00f0ingur \u00e1ri\u00f0 2015.<\/p>\n<\/div><\/div>","protected":false},"featured_media":1274,"template":"","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"default","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","ast-disable-related-posts":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-opacity":"","overlay-gradient":""}},"_phd_date_start":"2018-09-27T13:00:00+00:00","_phd_date_end":"2018-09-27T16:00:00+00:00","_phd_location":"A\u00f0albygging H\u00e1t\u00ed\u00f0asalur","_phd_admission":"A\u00f0gangur \u00f3keypis","_phd_thesis_title":"Ranns\u00f3knir \u00e1 sj\u00f3nr\u00e6nni athygli me\u00f0 s\u00f6fnunarverkefnum. Dynamics and flexibility of visual attention -Insights from a foraging perspective","_phd_source_url":"https:\/\/gamli.hi.is\/vidburdir\/doktorsvorn_i_salfraedi_tomas_kristjansson","_phd_source_node_id":"312057","_phd_source_type":"vidburdir","_phd_member_id":258,"footnotes":""},"phd_school":[60,75],"phd_discipline":[76],"class_list":["post-6021","phd_defence","type-phd_defence","status-publish","has-post-thumbnail","hentry","phd_school-heilbrigdisvisindasvid","phd_school-salfraedideild","phd_discipline-phd-i-salfraedi"],"_links":{"self":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_defence\/6021","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_defence"}],"about":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/types\/phd_defence"}],"version-history":[{"count":0,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_defence\/6021\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/media\/1274"}],"wp:attachment":[{"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/media?parent=6021"}],"wp:term":[{"taxonomy":"phd_school","embeddable":true,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_school?post=6021"},{"taxonomy":"phd_discipline","embeddable":true,"href":"https:\/\/phd.hi.is\/en\/wp-json\/wp\/v2\/phd_discipline?post=6021"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}