Mikrogenetička analiza percepcije ahromatskih površina

Abstract

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).