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Performance characteristics in a spatial-location task were examined nonmetrically. In Experiment 1, subjects reproduced the location of a dot either from immediate memory or while actually looking at the dot. Independent analyses of accuracy and the direction of incorrect reproductions yielded evidence for a fast-acting locational-memory process that may be distinct both from locational-perception processes and from response-bias processes. In Experiment 2, three different borders were used to vary the distance between the dot location and the border. Locational-memory accuracy increased as this distance decreased. Incorrect reproductions tended to occur toward rather than away from the border, and the robustness of this effect decreased for dot locations nearer to the border. Due to our nonmetric approach, the above conclusions are generalizable to all psychological conceptions whose spatial distances are monotonically related to the external spatial distances investigated here. A weighted-distortion theory of memory for spatial location is proposed to account for these and other findings.

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Hierarchically organized knowledge about actions has been postulated to explain planning in problem solving. Perdix, a simulation of problem solving in geometry with schematic planning knowledge, is described. Perdix's planning knowledge enables it to augment the problem space it is given by constructing auxiliary lines. The planning system also provides a mechanism that can result in problem solving set. Results of three experiments involving set and constructions seem consistent with the kinds of knowledge structures hypothesized in the model. Protocols given during solution of 11 geometry problems showed general agreement with the explanation of constructions and set based on planning knowledge, but they also indicated processes of human problem solving not represented in the model. Finally, the explanation of constructions is discussed in relation to the general question of ill-structured problems and creativity, and the explanation of set is discussed in relation to other phenomena in the problem solving literature, including functional fixedness.Several recent analyses of knowledge used in solving problems have hypothesized a structure in which knowledge about actions is hierarchical. Knowledge about each action includes knowledge about preconditions that are required for the action to be performed, knowledge about consequences of the action, and knowledge of the component subactions that are performed in the process of performing the more global action. A system based on this principle was developed by Sacerdoti (1977) in the domain of robotics, and systems designed along similar lines have been proposed for a number of other problem domains. These include an analysis of geometry theorem proving by Goldstein (Note 1), analyses of solving textbook problems in physics by Bhaskar and Simon (1977) and by Larkin (Note 2), an analysis of designing electrical circuits by Sussman (1977), an analysis of writing prose by Flower and Hayes (in press), analyses of designing computer programs by Atwood, Polson, Jeffries, and Ramsey (Note 3), Goldstein and Miller (Note 4), and Long (Note 5), and a general discussion by McDermott (1978). These theories are all consistent in a general way with earlier suggestions by Berlyne (1965), Duncker (1945), Hull (1930), Miller, Galanter, and Pribram (1960, and others regarding hierarchical structure of thinking and behavior. The more recent work has included hypotheses about the specific knowledge structures involved in performing the various kinds of tasks that have been studied. This paper presents an analysis of hierarchical knowledge for planning in solving textbook problems in high school geometry. A simulation model of problem solving called Perdix (Greeno, 1978) has been extended in a way that involves hierarchical planning knowledge. This development has provided two extensions of previous theories. First, an explanation is provided for the occurrence of constructions in problem solving. Second, the knowledge of global actions used in planning provides an explanation of pro...

Each year, a few days after the Nobel prize ceremony is held in Stockholm, Sweden, a discussion with the laureates in physics, chemistry and medicine is recorded for subsequent television broadcast. A question about scientific intuition recurs from year to year and is discussed on average for five minutes. Transcripts of 14 years of these parts of the discussions were analysed to illuminate the laureates' views of scientific intuition. Practically all laureates consider scientific intuition to be distinctly different from conscious, logical reasoning processes, and to concern the direction of research, more often the finding of a path than reaching the goal. The experience of intuition is frequently characterized as having a certitude based on a feeling or a perception of almost aesthetic or quasi-sensory nature. Scientific intuition seems to develop through extended and varied experiences of the object of research and is apparently based on an initially vague, global, not fully conscious, anticipatory perception of the solution searched for; a simultaneous grasp of the whole, well in advances of knowing its parts in detail.Scientific intuition seems to be a special case of intuitive thinking in general, which can be found also among very young children, in their dealing with simple arithmetic problems, for instance. It is suggested that one possible reason for the relative absence of intuitive understanding resulting from science education in schools is the lack of free and varied exploration of the phenomena dealt with.