i have to write an introduction using the same format did it but the professor said it was pagarized if you can pls help me
The phenomenology of perceptual organization was first extensively studied by the Gestalt psychologists (Wertheimer, 1923). They showed that similarity, proximity, and common movement of discrete elements are strong determinants of perceptual grouping. These simple principles maximize the chance of putting together parts of the same object and separating parts of different objects; presumably, they evolved for this reason. Some organisms have also evolved means of outwitting the parsing skills of their predators, using camouflage to break up local continuities of color, brightness, line, or texture (Fox, 1978).
The manner in which similarity controls perceptual grouping was further explored by Beck (1966, 1967) and by Olson and Attneave (1970). Beck found that differences in line orientation could be as effective as differences in brightness in segregating two groups of elements. A display divided into regions containing Ts and tilted Ts segregates easily, whereas one divided between Ts and Ls does not. Beck suggests that similarity grouping is “fundamentally an acuity task involving the simultaneous discrimination of stimulus differences prior to a narrowing or focusing of attention” (1972, p. 13). Any features that are easily discriminated with peripheral vision in a patterned visual field will also mediate grouping. Beck (1972) also showed that discriminability is determined differently when attention is focused and when it is spread across a display. Thus the advantage in discriminability of Ts versus tilted Ts compared to Ts and Ls dis- appears when single items are presented in an otherwise empty field.
Julesz (1975) tried to specify in statistical terms the properties that determine texture segregation. He proposed that the visual sys- tem automatically detects first- and second- order dependencies among local elements and segregates any areas that differ systematically at either of these two levels. Higher order dependencies are detected only slowly, with effort and “scrutiny”; they cannot mediate the spontaneous emergence of salient boundaries. Later, Caelli, Julesz, and Gilbert (1978) and Julesz and Caelli (1979) included as potential mediators of texture segregation a few specific higher order combinations, which represent the local geometric properties of collinearity, corner, and closure. Most recently, Julesz (1980) reduced to just two basic elements the local cues that he believes can distinguish textures sharing the same second-order statistics: these elements, which he calls “textons,” are (a) “elongated blobs” and (b) the number of line ends or “terminators.” The theories all agree that perceptual grouping occurs automatically and in parallel, without attention or “scrutiny,” as Julesz (1980) puts it. This pre attentive organization should then affect all subsequent stages of processing. Treisman, Sykes, and Gelade (1977) proposed a new hypothesis about the role of attention in the perception of objects that has implications for the nature and use of perceptual grouping. The theory suggests that focused attention is necessary for the accurate combination of features or properties of complex objects when- ever more than one object is presented in an unpredictable context. Separable features are registered independently and in parallel across the visual field. However, when subjects must be identified and no contextual cues are available to select the expected combinations of features, a correct synthesis can be achieved only by focusing attention on one location at a time. Features which co- occur in a single fixation of attention are combined to form an object.
If attention is diverted or overloaded, the features may be wrongly recombined, forming “illusory conjunctions” (Treisman & Schmidt, 1982). Treisman and Gelade (1980) tested this feature-integration theory of attention in several experiments. We showed that visual search for targets defined by one or more disjunctive features (e.g., blue or curved) occurs in parallel across a spatial display, whereas search for a conjunction target (e.g., red and vertical) requires a serial, self-terminating scan through items in the display, suggesting that attention must be focused on each item in turn. The linear functions and 2:1 slope ratio of negative to positive search times were maintained across two different levels of target/distractor discriminability, which produced markedly different search rates (40 milliseconds and 92 milliseconds per item). The serial scan for conjunction targets was there- fore not due to the overall level of difficulty. Conversely, a difficult feature search (for ellipses differing slightly in size) produced very slow search rates but neither linear functions nor 2:1 slope ratios.
In a different paradigm, we showed that feature targets can be identified without being correctly localized, whereas for conjunction targets, identity and location appear to be interdependent. The interdependence is consistent with the claim that conjunctions are correctly registered only when attention is focused on the relevant location. Finally, when attention is diverted or overloaded, illusory conjunctions of features are in fact experienced (Prinzmetal, 1981; Treisman & Schmidt, 1982). Illusory objects may recombine either dimensions, like the shape, size, and color of different real objects, or component parts, like the curves, lines, and angles of more complex linear functions, but the fact that attention limits are implicated in the formation of illusory conjunctions and in the accurate localization of conjunction targets makes it plausible in conjunction search to attribute the linear increase in latencies with in- creased display size to a serial self-terminating scan with focused attention directed to each item in turn.
The relation between attention and perceptual grouping has been discussed by Kahneman and Henik (1977). They describe a phenomenon that they call “group processing.” Group processing in the report of tachistoscopic arrays is characterized by similar and highly correlated probabilities of report for items within the same perceptual group and by discontinuities and negative correlations in the probabilities of re- port for items in different groups.
Kahneman and Henik (1977) suggested that attention is allocated in a hierarchical fashion, first to a group as a whole and only subsequently to elements within a group. They also looked at selective attention in relation to the degree of spatial segregation or mixing of red and blue letters. In attempting to recall the red letters only, subjects showed a marked advantage of grouped displays compared to a checkerboard arrangement. The results suggest that attention can only (or much more effectively) be focused on relevant items if these are spatially grouped.
The phenomenology of the perceptual organization was first extensively studied by the Gestaltpsychologists (Wertheimer, 1923). They showed that similarity, closeness, and common movement of…
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