PerceptualandMotorSkills, 1992, 74, 827-831. O Perceptual and Motor Skills 1992 MEASURING THE TYPICALITY OF OBJECTS INCLUDED IN ENVIRONMENTAL SCENES: A FIRST SCALE ' FRANCESC S. BELTRAN AND SALVADOR HERRANDO Laboratori de Visi6 Universitat de Barcelona MANUEL PELEGRINA Lnborafori de Psicologia Experimental Universitat Ramon Lull Summary.-Many researchers have been using the concept of "typicality" to ex- plain the influence of knowledge structures on processing visual stimuli. In this paper we try to establish a preliminary method for measuring the typicality of natural objects contained in environmental scenes. The results are discussed in the context of research on how objects in scenes are identified. We also suggest that scales of typicality con- tinue to be developed. Recent theories about. perception have been focussed on describing the simultaneous interaction of the object's physical characteristics and the sub- ject's knowledge structures in processing visual information (e.g., Rock, 1785; Dark, 1980; Pezdek, Whetstone, Reynolds, Askari, & Dougherty, 1989). Moreover, empirical research has established the importance of semantic ele- ments in the identification of visual stimuli (e.g., Flowers & Lohr, 1985; Friedman, 1979; Virzi & Egeth, 1984). The results of this research suggest that there exist some elements in the stimulus which may help to focus at- tention, namely, so-called "typical elements" (Chastain & Ersoff, 1977; Os- try, Moray, & Marks, 1776; Pashler, 1984). "Typicality," defined as the suitability of a given element in a contex- tual situation (Flowers, Polansky, & Karl, 1981; Staller & Lappin, 1981; Malt & Smith, 1782), has been widely used in research on knowledge struc- tures employing visual material, such as real environmental scenes (e.g., Bie- derman, 1981; Biederman, Mezzanotte, & Rabinowitz, 1982; Loftus & Mack- worth, 1978; Palmer, 1975; Pezdek, 1978). In this context of research, "scenes" are usually defined as an organized set of objects from the real world, which maintain specific spatial relationships as between themselves (Mandler & Parker, 1976; Tversky & Hemenway, 1983). From the above point of view, "typicality" is an effect of familiarity, 'This research was partially aided by a DGICYT Grant PS88-0028 from the Spanish Gov- ernment, and by a CIRIT Grant AR88 from the Catalan Government. We thank anonymous referees for comments and suggestions regarding an earlier version of the manuscript. Requests for reprints should be sent to Francesc S. Beltran, Departament de Psicologia Experimental (Laboratori de Visib), Universitat de Barcelona, 08028 Barcelona, Spain.