Solving combinatorial problems: The 15-puzzle

We present a series of experiments in which human subjects were tested with a well-known combinatorial problem called the 15-puzzle and in different-sized variants of this puzzle. Subjects can solve these puzzles reliably by systematically building a solution path, without performing much search and without using distances among the states of the problem. The computational complexity of the underlying mental mechanisms is very low. We formulated a computational model of the underlying cognitive processes on the basis of our results. This model applied a pyramid algorithm to individual stages of each problem. The model's performance proved to be quite similar to the subjects' performance.     

Constant capacity in an immediate serial-recall task: a logical sequel to Miller (1956)

We assessed a hypothesis that working memory capacity should include a constant number of separate mental units, or chunks (cf. Miller, 1956). Because of the practical difficulty of measuring chunks, this hypothesis has not been tested previously, despite wide attention to Miller's article. We used a training procedure to manipulate the strength of associations between pairs of words to be included in an immediate serial-recall task. Although the amount of training on associations clearly increased the availability of two-item chunks and therefore the number of items correct in list recall, the number of total chunks recalled (singletons plus two-word chunks) appeared to remain approximately constant across association strengths, supporting a hypothesis of constant capacity.     

Does each hemisphere monitor the ongoing process in the contralateral one?

The present study was conducted to examine hemispheric division of labor in the initial processing and error monitoring in tasks for which hemispheric specialization exists. We used lexical decision as a left hemisphere task and bargraph judgment as a right hemisphere task, and manipulated cognitive load. Participants had to respond to one of two stimuli presented to both visual fields and were instructed to correct their errors. To achieve enough correctable errors, participants were encouraged to respond quickly by using a bonus system. The results showed the classical asymmetry for initial responses in both tasks and reversed asymmetry for corrections in the bargraph task at both load conditions, and in the lexical decision task at the high load condition. The results suggest that each hemisphere monitors the ongoing process in the contralateral one and that the dissociation of initial process and its monitoring grows with load of task.     

Implicit contributions of context to recognition

Studies of the impact of context on remembering have not focused on the influence of contextual contingency on subsequent recognition in the condition in which the contingency cannot be verbalized. In two experiments, we analyzed the effect of an implicitly encoded position contingency involving location and semantic category on both hit and false alarm recognition judgments after 1 day and 1 week delays. We vigorously probed for what participants could say about the contingency. We found context effects for both hits and false alarms, whether or not participants could verbalize any knowledge they might have of contingency. These results suggest that people may use contextual information when making a recognition judgment even if they are not aware of this information.     

Adult age differences in episodic memory: further support for an associative-deficit hypothesis

This study further tested an associative-deficit hypothesis (ADH; M. Naveh-Benjamin, 2000), which attributes a substantial part of older adults' deficient episodic memory performance to their difficulty in merging unrelated attributes-units of an episode into a cohesive unit. First, the results of 2 experiments replicate those observed by M. Naveh-Benjamin (2000) showing that older adults are particularly deficient in memory tests requiring associations. Second, the results extend the type of stimuli (pictures) under which older adults show this associative deficit. Third, the results support an ADH in that older adults show less of an associative deficit when the components of the episodes used are already connected in memory, thereby facilitating their encoding and retrieval. Finally, a group of younger adults who encoded the information under divided-attention conditions did not show this associative deficit.     

Visual context integration is not fully developed in 4-year-old children

Long-range horizontal interactions supporting contour integration were found to be weaker in children than in adults (Kovács et al, 1999 Proceedings of the National Academy of Sciences of the USA 96 12204-12209). In the present study, integration on a larger scale, between a target and its context was investigated. Contextual modulation of the percept of a local target can be directly measured in the case of geometric illusions. We compared the magnitude of a size contrast illusion (Ebbinghaus illusion or Titchener circles) in children and adults. 4-year-old children and adults performed 2AFC size comparisons between two target disks in the classical Ebbinghaus illusion display and in two other modified versions. We found that the magnitude of the illusion effect was significantly smaller in children than in adults. Our interpretation is that context integration is not fully developed in 4-year-old children. Closer-to-veridical-size estimations by children demonstrate that the perception of the local target is less affected by stimulus context in their case. We suggest that immature cortical connectivity is behind the reduced contextual sensitivity in children.     

Universal sex differences in the desire for sexual variety: tests from 52 nations, 6 continents,and 13 islands

Evolutionary psychologists have hypothesized that men and women possess both long-term and short-term mating strategies, with men's short-term strategy differentially rooted in the desire for sexual variety. In this article, findings from a cross-cultural survey of 16,288 people across 10 major world regions (including North America, South America, Western Europe, Eastern Europe, Southern Europe, Middle East, Africa, Oceania, South/Southeast Asia, and East Asia) demonstrate that sex differences in the desire for sexual variety are culturally universal throughout these world regions. Sex differences were evident regardless of whether mean, median, distributional, or categorical indexes of sexual differentiation were evaluated. Sex differences were evident regardless of the measures used to evaluate them. Among contemporary theories of human mating, pluralistic approaches that hypothesize sex differences in the evolved design of short-term mating provide the most compelling account of these robust empirical findings.     

Code-switching across brainstorming sessions: implications for the revised hierarchical model of bilingual language processing

The revised hierarchical model (RHM) of bilingual language processing posits independent word form representations for the dominant language (L1) and the nondominant language (L2), facilitated translation from L2 words to L1 words, access to common concepts for L1 and L2, and stronger activation of concepts for L1 than for L2. Spanish-English and English-Spanish bilinguals brainstormed for two sessions; half switched languages (L1-L2 or L2-L1) and half stayed in the same language (L1-L1 or L2-L2) across sessions. In both sessions, L1 brainstorming resulted in more efficient idea productivity than L2 brainstorming, supporting stronger concept activation for L1, consistent with the RHM. Switching languages from L2 to L1 resulted in the most efficient idea productivity in Session 2, suggesting that switching to L1 not only permits strong concept activation, but also the activation of concepts that are relatively different than those activated by L2, inconsistent with the RHM. Switching languages increased the proportion of Session 1 ideas repeated during Session 2, despite instructions not to repeat. This finding suggests that there is activation of concepts as well as word forms in same language brainstorming and that this dual activation aids in following instructions not to repeat, consistent with the RHM. It is suggested that the RHM be re-specified to accommodate the notion that L1 and L2 access relatively different concepts.     

西方哲学过去十年的主要进展

我现在谈一下西方哲学在过去１０年的进展,并就下一个世纪哲学的发展提出自己的看法。这两个任务都很艰巨。如果考虑一下过去１０年这个暑期学院的研讨班和讨论会,我们就会对哲学所涵盖的课题范围有所了解。这些研讨班和讨论会所涉及的论题包括伦理学、认识论、心的哲学、女性主义思想和科学哲学等。在这篇简短的文章中,我不可能充分讨论所有这些领域中的进展,更不要说哲学中的许多其他领域了。所以,我要有所选择而只是提及哲学在过去１０年的许多进展中的少数几个。我首先要谈的问题,有时被称为“信息爆炸”的问题。近些年来,我们在…