Visual Search - PsyToolkit

Searching is a fundamental human activity. In visual search tasks, people are asked to find a visual stimulus amongst other visual stimuli ... VisualSearch main|lessons|copyright Introduction Doityourself Whyisitimportant? Ideasforhomework Readingmaterial Introduction Definition Searchingisafundamentalhumanactivity.In visualsearchtasks, peopleareaskedtofindavisualstimulusamongstothervisual stimuli(distracters).Themorestimulithereare,themoretimeit takestofindatargetstimulus. Inavisualsearchexperiment,atargetistheitemthatyouneed tofind.Adistracterordistractorisanitemthatyouarenot lookingfor,andwhichdistractsyoufromfindingthetarget. Bytheway,distracteranddistractorarejustdifferentwaysof spelling,bothcorrect. Examplesofvisualsearchinreallife Searchingforkeysonamessytable Searchingforyourwallet Searchingforteabagsinthesupermarket Searchingforyournameonalistofnames Psychologistshavestudiedhowwesearch,andwhatcanmakesearch easyandwhatcanmakesearchhard.Forexample,trythefindared circleinthepictureontheleftandinthepictureontheright.In bothcases,thereisjustoneredcircle,butitismucheasieronthe left.Theredcircle"standsout",thisisknownasthepopout phenomenon. Intheexampleontheright,thetimeittakesontofindtheobject dependsonhowmanynontargets(distractors)thereare.Themorethereare,the longerthesearchtime.Inthefigurebelow,youseethedataof160 trials.Therewerebetween5and20itemsonscreen.Themoreitems, thelongerthesearchtime.Theredlineisthesearchslope. Inmanyvisualsearchexperiments,stimuliaremultidimensional.For example,inthedemo,youneedtofindastimulusthatvariesontwo dimensions,color(orangeorblue)andshape(normalorupsidedown T).AllyouneedtodoistodecidewhetherthereisanormalorangeT (notanupsidedownone!)andifso,youpressabutton.Thecomputer measuresthetimeittakesyoutopressthebutton.Inavisualsearch experiment,thistimecanbecalledthesearchtime. Searchingforaspecificcombinationoftwostimulusfeatures(suchas anupsideandorangeT)iscalledconjunctivesearch.Ina conjunctivesearch,youlookforthecombination,thatisthe conjunctionoftwofeatures.Conjunctivesearchismoretimeconsuming thansearchforonefeature.Belowisaretwoexamplesofconjunctive search.ItisstillrelativeeasytofindtheorangeT,butthatis onlybecausetherearesofewdistracters. Inthefigurebelow,youseetwoexampletrials.Thesearchtargetis onlypresentinthepanelontheleft.Also,notethatontheleft thereare6itemsonscreen,andontherightonly5.Thefeweritems onscreen,theeasieritistomakeyourdecision. Doityourself Inthedemo,youneedtofindanorangeT.Thenumberofdistractors varies.ThedistractorscanbeanupsidedownorangeTandablue T.Ifyousavethedata(youneedtodownloadallfilestodoso),you cancalculateyourownsearchslope. Clickheretorunademoofthevisualsearchtask Whyisitimportant? Psychologistsstudyfundamentalpsychologicalprocesses,andoneof themissearching.Searchingisnotjustimportantinmodernlife.Our ancestorsweredependentonfindingfood.Hunterssearchformoving animalsandgathererssearchforvegetables,fruits,nuts, mushrooms.Youcanimaginehowdifficultitcanbetofindtheseitems amongstallthenon-edibleitemswhichmightlooksimilar.Indeed, efficientsearchingandgatheringhasevolutionaryadvantages. Ideasforhomework Doyouthinkthatmenandwomenareequallygoodatsearching?How doesthisrelatetoevolutionarytheories?Whatdoweknowaboutsex differencesinvisualsearch? Allthestimuliinthedemonstrationusemultidimensional stimuli.Designanexperimentinwhichyoucomparestimulithatvary onjustonedimension,suchascoloredcircles,withstimulithat varyontwodimensions(colorandshape). Whatdoesthesteepnessofthesearchslopetellusabouthowwe search? Readingmaterial Treisman,A.(1977).Focussedattentionintheperceptionand retrievalofmultidimensionalstimuli.PerceptionandPsychophysics, 9,40-50. Stoet,G.(2011).Sexdifferencesinsearchandgatheringskills.EvolutionandHumanBehavior,32,416-422. Lastupdated2021-01-2716:42:31CET