Mapping the mental space of rectangles.

The cognitive structure of a shape space--the space of rectangles--is explored by a nonmetric scaling technique. Our experiment was designed to extract the major transformational paths or 'modes' that characterize the mental shape space. Earlier studies of rectangle similarities using multidimensional scaling have provided conflicting evidence about whether the coordinate system of the mental rectangle space is based on height and width or on area and shape (i.e. aspect ratio). Our study reveals shape to be the single dominant factor. We suspected that earlier evidence for a height-width parameterization might have been due to the presentation of rectangles upright in a pseudo-gravitational coordinate system (whereas our rectangles are randomly rotated). In a control experiment with upright (vertical or horizontal) rectangles, the heavy bias towards shape preservation was still the dominant mode. In addition, however, a secondary bias towards change of height or width emerged, exactly following the pattern expected from the biasing change in context. This finding established a concrete path by which context and frame can influence the way shape is represented. The relevance of these findings to the cognitive organization of more complex shape spaces is discussed.     

Misreadings by beginning readers of Serbo-Croatian

Errors in reading aloud by the beginning reader have been interpreted as reflecting the difficulty and the importance of phonemic segmentation for the acquisition of reading skills. Results from previous studies on English words patterned as consonant-vowel-consonant showed: (1) more errors on vowels than on consonants; (2) more errors on word final consonants than on word initial consonants; and suggested that (3) consonant errors were based on phonetic confusions while vowel errors were not. In contrast to their English counterparts, the beginning readers of Serbo-Croatian tested in the present study committed proportionally fewer errors on their reading of vowels than of consonants but in common with their English counterparts, their reading of final consonants was more vulnerable to error than their reading of initial consonants. This pattern of errors was found for both word and pseudoword consonant-vowel-consonant structures and the pattern of vowel confusion, like the pattern of consonant confusions, was rationalized by speech-related factors. The differences between the patterns of confusions for Serbo-Croatian and for English could be due to the difference between the two orthographies in the precision with which they represent the phonology or to the fact that the vowels of English are qualitatively less distinct phonologically than the vowels of Serbo-Croatian.     

Decision theory and artificial intelligence II: The hungry monkey

This paper describes a problem-solving framework In which aspects of mathematical decision theory are incorporated into symbolic problem-solving techniques currently predominant in artificial intelligence. The utility function of decision theory IS used to reveal tradeoffs among competing strategies for achieving various goals, taking into account such factors as reliability, the complexity of steps in the strategy, and the value of the goal. The utility function on strategies can therefore be used as a guide when searching for good strategies. It is also used to formulate solutions to the problems of how to acquire a world model, how much planning effort is worthwhile, and whether verification tests should be performed. These techniques are illustrated by application to the classic monkey and bananas problem.     

Niche construction, biological evolution, and cultural change

We propose a conceptual model that maps the causal pathways relating biological evolution to cultural change. It builds on conventional evolutionary theory by placing emphasis on the capacity of organisms to modify sources of natural selection in their environment (niche construction) and by broadening the evolutionary dynamic to incorporate ontogenetic and cultural processes. In this model, phenotypes have a much more active role in evolution than generally conceived. This sheds light on hominid evolution, on the evolution of culture, and on altruism and cooperation. Culture amplifies the capacity of human beings to modify sources of natural selection in their environments to the point where that capacity raises some new questions about the processes of human adaptation.     

Accuracy and differentiation in social prediction: A developmental perspective1

Two studies examined the accuracy and differentiation of 4–5-yearolds‘, 8–9-year-olds’, and undergraduates' predictions of the preferences of peers and nonpeers. In Study 1 each subject was presented with separate arrays of snacks, meals, and activities depicted on cards and were asked to select their own preferences and the preferences of peers and nonpeers (“grown-ups” for the children, and “4- to 5-year-olds” for the undergraduates). In Study 2 each subject selected his or her own preference, the preference of peers, and the preferences of both older nonpeers (“grown-ups”) and younger nonpeers (“2-year-olds”). For all age groups, including 4–5-year-olds: (1) the preference predictions differentiated peers from nonpeers, as well as older nonpeers from younger nonpeers; (2) it was very rare for a subject to select his or her own preferences for the preference predictions of both peers and nonpeers. There were no consistent developmental differences either in the tendency to select one's own preferences when predicting the preferences of others or in the tendency to differentiate predictions for peers and nonpeers. In contrast, there was a clear developmental increase in predictive accuracy, with 4–5-year-olds being relatively inaccurate in predicting the preferences of nonpeers. The inadequacy of constructs such as “assumed similarity” and “egocentrism” as explanations for the general accuracy in predicting peers' preferences and the 4–5-year-olds' inaccuracy in predicting nonpeers' preferences is discussed. Possible alternative variables underlying developmental increases in judgmental accuracy, such as “social reference,”“self reference,” and “social category knowledge,” are then proposed.     

Repetition priming is not purely episodic in origin

The sufficiency of similarity among surface attributes of prime-target pairs to account for the pattern of facilitation obtained in the repetition priming paradigm was evaluated. In Experiment 1, morphological primes were singular, inflected case forms of Serbo-Croatian words and visual similarity of prime and target was manipulated by alternating the two alphabets in which the Serbo-Croatian language is written. Results indicated that the magnitude of facilitation in the alphabetically alternating condition was not reduced relative to the nonalternating condition (RUPI-RUPI vs. RUPI-RUPI) which suggested that visual similarity is not a necessary condition for facilitation in the present task. In Experiment 2, related pairs included (a) base forms with diminutives, a class of highly productive and semantically predictable derivations marked in Serbo-Croatian by suffixes and (b) base words with morphologically unrelated monomorphemic words whose orthographic pattern encompassed the target in initial position and a sequence of letters in final position that elsewhere functions as a diminutive suffix. No facilitation of word targets by orthographically similar but morphologically unrelated primes was observed although there was a tendency toward facilitation among structurally similar pseudowords. Collectively, the experiments suggested that structural similarity of prime and target is not a sufficient condition for facilitation in the repetition priming paradigm.