Je li pažnja neophodna u opažanju

This research was conducted to investigate the phenomenon of inattentional blindness, which, examines the possibility of perception without visual attention. This study also attempted to determine whether certain features of stimuli can have an effect on the degree of that phenomenon. The study comprises three experiments, in which the procedure was exactly the same, but the type of presented stimuli differed. Thirty subjects participated in each experiment. They were randomly divided into three groups, which corresponded to three experimental conditions. The total sample consisted of 90 subjects. The results of Experiment 1 and Experiment 2 show that there is no adequate perception without active engagement of attention, while the results of Experiment 3 indicate that certain type of stimuli can be perceived automatically, without visual attention. Analysis of all results suggests that there is the effect of type of stimuli on seeing a stimulus in inattentional conditions, but not on accuracy of identification.Ovo istraživanje je provedeno s ciljem ispitivanja fenomena sljepila zbog nepažnje, tj. mogućnosti opažanja bez angažiranja vizualne pažnje. Ova studija je, također, pokušala utvrditi da li određene karakteristike podražaja utječu na količinu tog fenomena.Istraživanje čine tri eksperimenta u kojima je procedura bila potpuno ista, ali su se razlikovali tipovi prezentiranih podražaja. U svakom eksperimentu je sudjelovalo 30 ispitanika, koji su slučajnim odabirom podijeljeni u tri grupe kojima su odgovarala tri eksperimentalna uvjeta. Ukupan uzorak je činilo 90 ispitanika. Rezultati Eksperimenata 1. i 2. pokazuju da ne postoji adekvatna percepcija bez aktivnog angažiranja pažnje, dok rezultati Eksperimenta 3. pokazuju da određen tip podražaja može biti percipiran automatski, bez sudjelovanja vizualne pažnje. Analiza svih rezultata upućuje na zaključak da postoji utjecaj tipa podražaja na opažanje podražaja u uvjetima nepažnje, ali ne i na točnost identifikacije

Perceptive effects of image distortion

Ispitivana je perceptivna osetljivost na promene u kvalitetu vizuelne stimulacije. Kao sredstvo variranja kompleksnosti stimulacije korišćen je JPEG filter primenjen na kompjuterskim slikama koje su bile stimulusi u dva eksperimenta. U prvom eksperimentu ispitanici su na skali kvaliteta procenjivali efekte degradacije na tri fotografije različite perceptivne kompleksnosti. Ustanovljena je negativna korelacija između stepena degradacije slike i procene kvaliteta, a faktor kompleksnosti slike se pokazao kao značajan. U drugom eksperimentu korišćen je zadatak vizuelne diskriminacije. Ispitanici su diskriminisali parove fotografija sačinjene od jedne nedegradirane fotografije i jedne degradirane u različitom stepenu. Stepen degradacije je išao od jedne do deset JPEG jedinica. Analize pokazuju da je faktor kompleksnosti značajan i da uspeh u vizuelnoj diskriminaciji varira u funkciji razlike kvaliteta fotografija u paru.In the present study perceptive tolerance on image distortion was investigated. JPEG filer was used as a tool for degrading computer images, which were presented in two experiments. In the first experiment, subjects were estimating the effects of distortion on three images with different perceptive complexity. Regression analysis suggests that the distortion (JPEG quality) factor is a good predictor of estimated quality. The greater JPEG quality factor, the lower estimated quality of distorted image. In the second experiment, visual discrimination task was used. Subjects were discriminating pair of images (same / different) made by original, not distorted and distorted image with a different JPEG quality factor. Ranges of JPEG quality factor varied from one to ten JPEG units. Analyses shows that the factor of image complexity was statistically significant, indicating that visual discrimination is dependent on quality difference between images

Perception of illusory contours: a spatiotemporal characteristics

Jedno od pitanja koje se može postaviti u vezi prirode procesa percepcije iluzornih kontura jeste nivo njihove obrade. Fiziološke studije ubedljivo govore o tome da se ovaj fenomen može tretirati kao osnovno svojstvo vizuelne stimulacije. Primenom raznovrsnih tehnika registrovanja moždane aktivnosti, neurofiziolozi su otkrili specijalizovane neurone u zoni vizuelnog korteksa koji su osetljivi na iluzorne konture. Psihofizički, fenomen ranog viđenja iluzornih kontura nije u potpunosti potvrđen. U psihološkoj literaturi postoje suprostavljena stanovišta. Deo eksperimenata govori u prilog tezi o ranom viđenju, dok drugi deo govori suprotno. Jedna od problema našeg istraživanja je nivo obrade iluzornih kontura, operacionalizovan kroz metodologiju vizuelne pretrage. U okviru ovog problema proveravali smo i model 'vezivanja pozadinskih elemenata' koji je ponuđen kao jedno od objašnjenja opažanja mete u osnovnim vizuelnim pretrsgama. Đrugi problem rads prsdstavijs ispitivanje vremenskih karakteristika faktora koji utiču na pretraživanje mete. To su pre svega, karakteristike mete i njena lokacija u setu vizuelne pretrage. Posebna tema istraživanja bilo je utvrđivanje vremenskog perioda potrebnog za formiranje percepta iluzorne figure. Razvijena je specifična eksperimentalna tehnika kojom smo ovaj period utvrdili. U suprotnosti sa jednim delom psihofizičkih istraživanja, naše istraživanje je pokazalo da se iluzorne konture ne mogu obrađivati na nivou ranog viđenja. Međusobnim poređenjem uloge karakteristike i lokacije mete, utvrdili smo da je lokacija ima važniju ali ne i nezavisnu ulogu od uloge karakteristike mete. Kritično vreme, potrebno za kompletiranje percepta iluzornih kontura iznosi oko 150 ms. Takođe, pokazalo se da su svi faktori, obuhvaćeni našim istraživanjem relativno nezavisni od dejstava prostornih činilaca stimulusne organizacije.One of the issues related to the perception of illusory contours is the level of their processing. In physiological studies, this phenomenon is explained in terms of basic properties of visual stimulation. Applying various techniques of brain activity monitoring, neurophysiologists have detected specialized neurons in the visual cortex that are sensitive to illusory contours. Psychophysically, early vision of illusory contours phenomena is not yet confirmed. However, in literature, conflicting explanation can be found. Some experiments support the early vision hypothesis, whilst other reject it. The present study addresses two major topics related to the perception of illusory contours, as indicated by the visual search paradigm. Specifically we were evaluating the “binding of background elements” model. The other problem is related to temporal characteristics of factors that influence target search. These factors were target features and its location in visual search set. In particular we were interested in temporal parameters that elicit illusory contour formation. This was done by specific experimental procedure developed at the Laboratory of Experimental Psychology in Belgrade. In contrast to some approaches in psychophysics, the results of this study indicate that illusory contours can not be processed at the level of early vision. Comparing the roles of target features and target location, we concluded that location had more a important, although not independent role. The critical time required for completion of illusory contours percept was 150 ms. It was also shown

Role of symmetry and simplicity in shape disruption perception tasks

Purpose of the present research was further examination of roles of symmetry and complexity in visual perception tasks. We tested hypothesis from perceptual economy theory, and since we used shape disruptions as one of the stimulus characteristics we could also address Luccio's two step theory concerning perception of shape disruptions on good forms. Four experiments were conducted, visual search and simultaneous and delayed matching. Symmetry and complexity were varied, as well as set size in visual search experiment. Dependent variables were reaction time and error number. In all four experiments, symmetry had dominant effect, while significant effect of complexity was registered only in Experiment 1. However, in first three experiments interaction of symmetry and complexity was also significant. Analysis of reaction times and performance suggested that our results follow the pattern suggested by perceptual economy, i.e. that symmetry is dominant in easier tasks, while complexity was significant in most difficult task. Our results couldn't completely support Luccio's assumption that shape disruption is better perceived on good forms, although it can't be completely discarded

Microgenetic analysis of transparency perception

U ovom radu ispitivana je mikrogeneza opažanja providnosti. Pokušali smo da odgovorimo na pitanje da li se opažanje providnosti ahromatskih površina uspostavlja na nivou ranog opažanja (do 200 ms) ili pretpostavlja ulogu pažnje (nakon 200 ms). Dva preklapajuća kvadrata predstavljala su osnovi model za konstrukciju stimulusa. Na taj način definisane su tri površine: forma u obliku ćiriličnog slova Г, obrnutog latiničnog slova L i mali kvadrat ugnježden između ove dve forme. Podloga je bila crna, a stepen sivog ove tri površine variran je tako da se dobiju tri perceptivna efekta: providnost, osvetljenost i mozaik. Sva tri stimulusa mogu se definisati lokalno (tri površine jedna uz drugu) ili globalno (dva preklopljena kvadrata). Eksperiment se sastojao u primeni tehnike primovanja i zadatka isto-različito. Test figure su bile globalne (kvadrati) ili lokalne (L forme). Prim stimulusi bili su identični (prim = test) i perceptivni (providni, osvetljeni i mozaični). Trajanje prima je bilo 50 i 400 ms, a ISI 30 ms. Deset ispitanika odgovaralo je da li su test figure iste (npr. dva kvadrata) ili različite (kvadrat i L forma). Rezultati pokazuju da na obe ekspozicije identični primovi ne pokazuju diferencijalni efekat na RT: oba tipa test figura obrađuju se istom brzinom. Međutim, registrovan je diferencijalni efekat perceptivnog prima na RT: perceptivno primovane globalne test figure obrađuju se brže od lokalnih test figura. Ovi rezultati pokazuju da se kompleksni perceptivni opisi (npr. poluprovidni kvadrati) uspostavljaju veoma rano u procesu opažanja (pre 50 ms).In this study the microgenesis of transparency perception was investigated. Two intersecting squares were used as a basic stimulus model. Three surfaces was defined: surface which had the shape of capital Greek letter gamma, surface which had the shape of mirrored L and the little square nested between gamma and L. The gray levels of these surfaces were varied, whereas the background was constantly black. The gray levels variation can produce either transparency, spotlight or mosaic perception. All three categories can be described both locally (three juxtaposed surfaces) and globally (two overlapping squares). The primed matching paradigm and the same-different task were used. The global (squares) and the local (gammas or mirrored Ls) test stimuli were given as same or different pairs. There were the two prime types: identical (equal to test stimuli) and perceptual (related to the transparency, spotlight or mosaic). Prime duration were 50 ms and 400 ms, and the ISI was 30 ms. Ten subjects were asked to respond whether the test stimuli are same or different. The main result indicate that the difference in RT between perceptually primed global and local test stimuli is highly significant in both prime duration conditions and for transparency and spotlight patterns, and is marginally significant for mosaic patterns. The difference was such that the global tests were processed faster than the local tests. These results suggest that complex perceptual descriptions (transparency and the spotlight) are generated very early in the perceptual process (50 ms)

Unrealistic optimism and decision making

Jedna od vodećih deskriptivnih teorija odlučivanja u uslovima rizika, teorija izgleda Tverskog i Kanemana, otkriva neodrživost normativnog objašnjenja donošenja odluke samo na osnovu principa maksimizacije očekivane korisnosti ishoda i ističe uticaj alternativnih faktora na donošenje odluka. Efekat okvira odnosi se na uticaj jezičke formulacije ishoda na opredeljenje između sigurne i rizične mogućnosti, u negativnom okviru ljudi su skloni riziku, dok ga u pozitivnom izbegavaju. Individualne odluke nisu vođene objektivnim verovatnoćama ishoda, već subjektivnim verovatnoćama koje zavise od poželjnosti tih ishoda. Nerealistično pesimistični ispitanici dodeljuju manje verovatnoće (u odnosu na grupni prosek) poželjnim ishodima, dok nerealistično optimistični ispitanici dodeljuju veće verovatnoće (u odnosu na grupni prosek) poželjnim ishodima. Istraživanje je izvedeno sa ciljem da se proveri pretpostavka o povezanosti nerealističnog optimizma i donošenja odluka u uslovima rizika. Očekivali smo da će optimisti biti skloniji riziku, a da će pesimisti izbegavati rizik, kao i da će ukoliko se ispolje, ovakve kognitivne tendencije biti otporne na efekat okvira. Primenjena je skala nerealističnog optimizma i upitnik sa zadacima donošenja odluka u uslovima rizika. Rezultati ukupnog uzorka i naknadno izdvojenih grupa pesimista i optimista pokazali su da na svim nivoima obrade dominira sklonost ka riziku koja je otporna na uticaj subjektivnih verovatnoća i okvira u kom je ishod prikazan.One of the leading descriptive theories of decision-making under risk, Tversky & Kahneman's Prospect theory, reveals that normative explanation of decisionmaking, based only on principle of maximizing outcomes expected utility, is unsustainable. It also underlines the effect of alternative factors on decision-making. Framing effect relates to an influence that verbal formulation of outcomes has on choosing between certain and risky outcomes; in negative frame people tend to be risk seeking, whereas in positive frame people express risk averse tendencies. Individual decisions are not based on objective probabilities of outcomes, but on subjective probabilities that depend on outcome desirability. Unrealistically pessimistic subjects assign lower probabilities (than the group average) to the desired outcomes, while unrealistically optimistic subjects assign higher probabilities (than the group average) to the desired outcomes. Experiment was conducted in order to test the presumption that there's a relation between unrealistic optimism and decision-making under risk. We expected optimists to be risk seeking, and pessimist to be risk averse. We also expected such cognitive tendencies, if they should become manifest, to be framing effect resistant. Unrealistic optimism scale was applied, followed by the questionnaire composed of tasks of decision-making under risk. Results within the whole sample, and results of afterwards extracted groups of pessimists and optimists both revealed dominant risk seeking tendency that is resistant to the influence of subjective probabilities as well as to the influence of frame in which the outcome is presented

Amodal completion of partly occluded figures: Effect of contour orientation

U ovom istraživanju ispitivali smo interakciju figuralnih faktora (kontinuitet forme, C, i simetrija, S) i orijentacije (vertikalno-horizontalna i kosa) pri amodalnom kompletiranju poluzaklonjenih figura. Koristili smo tehniku primovanja. Prim i test stimulusi izloženi su u dve orijentacione pozicije, normalnoj (0o) i kosoj (45o). Primovi su bile dve iste slike (jedna pored druge): CC (petouglovi, tj. zasečeni kvadrati) i SS (šestouglovi sa dve ose simetrije) i AA (amodalni sklopovi: krug koji prekriva amodalnu figuru; kao amodalna figura može se videti ili C ili S). Redosled izlaganja stimulusa bio je: prim 400ms, ISI 20ms i test figura do odgovora. Test figure su bili parovi isto, CC i SS, i parovi različito, SC i CS. Test figure isto imale su identične primove (CC = gt CC i SS = gt SS) ili amodalne primove (AA = gt CC i AA = gt SS). Subjektima je dat zadatak da odgovore da li su figure u test stimulusu iste ili različite. Analizirana su vremena reakcije za odgovore isto. Efekat amodalnog prima bio je slabiji (duže RT) od efekta identičnog prima. Faktor rotacione pozicije nije bio značajan. Dobijena je značajna interakcija prim x rotaciona pozicija kod C test figura: efekat amodalnog prima bliži je efektu identičnog prima kada su konture orijentisane vertikalno i horizontalno. Ovakva interakcija nije dobijena kod S test figura. Zaključili smo da su simetričnije forme (kakva je S figura) otpornije na primovanje od manje simetrične C forme.In present study the temporal dimension of amodal completion in visual occlusion was investigated. We supposed that the visual system prefers to complete normally (vertically-horizontally) oriented contours than the oblique ones. Using the prime-matching paradigm we investigated the strength of amodal primes effects on processing speed of relating test figures. Both, prime and test stimuli were presented in normal and oblique (45o) orientations. The primes were pairs of identical figures: CC (truncked squares), SS (hexagons) and AA (amodal patterns: circle occludes either amodal C or amodal S). Temporal distribution of stimuli: prime 400ms, ISIs 20ms and test figures until response. Test figures were the “same” pairs, CC and SS, and the “different” pairs, SC and CS. Each “same” test figures had its identical prime (CC = gt CC or SS = gt SS) and its amodal prime (AA = gt CC and AA = gt SS). The subjects were asked to answer whether the figures in test stimuli were same or different. The “same” RTs were analysed. The effect of amodal prime was systematically weaker (longer RT) than the effect of identical primes. Orientation was not significant factor. The significant partial interaction prime x orientation was obtained for C test figures: the effect of amodal prime was closer to effect of identical prime when the contour was normally oriented. In the case of S test figures the interaction was not obtained. We concluded that the more symmetric test figure (S) was resistant to the prime effect

Visual search of illusory contours: an attempt of automatization

Laboratory of Experimental Psychology, University of Belgrade Recent research, which was mostly focused on assessing the types of visual search of illusory contours, showed that visual search is dependent on factors like target configuration and task type. Some experimental research supports the theory of parallel search while other research supports the theory of serial search of illusory contours. The inconsistency is most likely due to the fact that various types of illusory contour configurations were used in set creation. Up to this point, our research indicated that the serial search is used in most cases. Some exceptions of search type have been proven in some modification of task type but nevertheless the search profile remained serial. In this article, we are reporting on two visual search experiments. The first experiment was an investigation of a specific feature of a Kanisza type illusory triangle, orientation. The validity of the profile defined in the first experiment was tested in our second experiment with an attempt to automatize the visual search by the multiplication of the initial experimental trials. Our results confirmed that, regardless of the number of experimental trials, the visual search profile remains serial

Perception of illusory contours: a spatiotemporal characteristics

Jedno od pitanja koje se može postaviti u vezi prirode procesa percepcije iluzornih kontura jeste nivo njihove obrade. Fiziološke studije ubedljivo govore o tome da se ovaj fenomen može tretirati kao osnovno svojstvo vizuelne stimulacije. Primenom raznovrsnih tehnika registrovanja moždane aktivnosti, neurofiziolozi su otkrili specijalizovane neurone u zoni vizuelnog korteksa koji su osetljivi na iluzorne konture. Psihofizički, fenomen ranog viđenja iluzornih kontura nije u potpunosti potvrđen. U psihološkoj literaturi postoje suprostavljena stanovišta. Deo eksperimenata govori u prilog tezi o ranom viđenju, dok drugi deo govori suprotno. Jedna od problema našeg istraživanja je nivo obrade iluzornih kontura, operacionalizovan kroz metodologiju vizuelne pretrage. U okviru ovog problema proveravali smo i model 'vezivanja pozadinskih elemenata' koji je ponuđen kao jedno od objašnjenja opažanja mete u osnovnim vizuelnim pretrsgama. Đrugi problem rads prsdstavijs ispitivanje vremenskih karakteristika faktora koji utiču na pretraživanje mete. To su pre svega, karakteristike mete i njena lokacija u setu vizuelne pretrage. Posebna tema istraživanja bilo je utvrđivanje vremenskog perioda potrebnog za formiranje percepta iluzorne figure. Razvijena je specifična eksperimentalna tehnika kojom smo ovaj period utvrdili. U suprotnosti sa jednim delom psihofizičkih istraživanja, naše istraživanje je pokazalo da se iluzorne konture ne mogu obrađivati na nivou ranog viđenja. Međusobnim poređenjem uloge karakteristike i lokacije mete, utvrdili smo da je lokacija ima važniju ali ne i nezavisnu ulogu od uloge karakteristike mete. Kritično vreme, potrebno za kompletiranje percepta iluzornih kontura iznosi oko 150 ms. Takođe, pokazalo se da su svi faktori, obuhvaćeni našim istraživanjem relativno nezavisni od dejstava prostornih činilaca stimulusne organizacije.One of the issues related to the perception of illusory contours is the level of their processing. In physiological studies, this phenomenon is explained in terms of basic properties of visual stimulation. Applying various techniques of brain activity monitoring, neurophysiologists have detected specialized neurons in the visual cortex that are sensitive to illusory contours. Psychophysically, early vision of illusory contours phenomena is not yet confirmed. However, in literature, conflicting explanation can be found. Some experiments support the early vision hypothesis, whilst other reject it. The present study addresses two major topics related to the perception of illusory contours, as indicated by the visual search paradigm. Specifically we were evaluating the “binding of background elements” model. The other problem is related to temporal characteristics of factors that influence target search. These factors were target features and its location in visual search set. In particular we were interested in temporal parameters that elicit illusory contour formation. This was done by specific experimental procedure developed at the Laboratory of Experimental Psychology in Belgrade. In contrast to some approaches in psychophysics, the results of this study indicate that illusory contours can not be processed at the level of early vision. Comparing the roles of target features and target location, we concluded that location had more a important, although not independent role. The critical time required for completion of illusory contours percept was 150 ms. It was also shown