SVIBOR - Project code: 6-06-025


Strossmayerov trg 4, HR - 10000 ZAGREB
tel.: +385 1 459 44 44, fax: +385 1 459 44 69


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Project code: 6-06-025


Main researcher: KOLESARI∆, VLADIMIR (21736)

Type of research: basic
Duration from: 04/01/91. to 04/01/94.

Papers on project (total): 11
Institution name: Filozofski fakultet - HumanistiŤke znanosti, Zagreb (130)
Department/Institute: Department of Psychology
Address: Salajeva 3,
City: 10000 - Zagreb, Croatia
Phone: 385 (0)1 6120-196
Fax: 385 (0)1 6120-037

Summary: Five laboratory investigations have been carried out. (1) In the experiment with simple reaction time as the dependent variable, its stability in time and dependance on stimuli context was elucidated. Reaction time may be affected by many factors which are irrelevant to the relationship of the independent and dependent variable, but subjects tend to have a similar reaction dynamics over longer time periods. Results suggest that the impact of stimuli context is to some extent cognitively mediated. The results of our recently conducted experiments, shich shows that subjects' reaction expectation are related to stimuli context support that conclusion.(2) The results obtained by the divided visual field technique are in keeping with the model presuming that the cerebral hemispheres are two processors, each comprising a number of subsystems and modules. Given that both hemispheres are able to process verbal stimuli, when interpreting the differences the characteristics of verbal and the mode of their presentation should be taken into account. (3) By effectuating total restriction of information on distance of the viewed object it was still possible to estimate its size: the size of the afterimage projected on the perceptually accessible distance was in accordance with the visual angle law. (4) The obtained direction of the difference in the perception of brightness of indirectly illuminated surfaces depends on the sharpness of illumination edges. This result is in keeping with the hypothesis that the color of an object is decoded on the basis of the sharpness of edges which, in turn, depends on the magnitude of indirect light. (5) Exponents of psychophysical functions obtained by the magnitude estimation method with or without a presented standard did not differ significantly. Various calculation techniques of the exponent in the situation without the standard yielded equal values.

Keywords: reaction time (RT), stimuli context, preparatory interval, visual afterimage, visual perception, achromatic perception, lexical decision, divided visual field technique, lateral dominance, method magnitude estimation

Research goals: The general objective of the project was to explore, by carefully designed and performed laboratory experiments, several basic issues on the functioning of the human as a reactive system. To this end experiments were carried out in the field of visual and auditory perception (input), cerebral hemispheric function (central processing), and motor reaction in its simple form, i.e. simple sensorimotor reaction (output). Given that these are basic issues of scientific psychology, the obtained results are only one of the contributions to the issues raised, although the mentioned stages of functioning have many dimensions and may be explored in a variety of ways. Considering the results of the particular experiments the conclusion may be reached that the objective has been met: data on reaction time stability and stimuli context impact have been obtained; it has been found that it is not warrantable to interpret all differences between left and right visual fields as a result of hemispheric specialization; that it is possible to objectively assess the apparent size of the object image; that the perception of indirect illumination depends on the sharpness of edges of perceived surfaces; that various procedures of the determination of the psychophysical function exponents do not yield significantly different values.

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Last update: 10/10/95