Determinants of human performance on concurrent schedules.

Six experiments, each with 5 human adults, were conducted to investigate the determinants of human performance on multiple concurrent variable-interval schedules. A two-key procedure was employed in which subjects' key presses produced points exchangeable for money. Variables manipulated across experiments were (a) changeover delay (Experiments 2, 4, and 6), (b) ordinal cues related to scheduled reinforcement frequencies (Experiments 3 and 4), and (c) instructions describing the ordinal relations between schedule-correlated stimuli and scheduled reinforcement frequency (Experiments 5 and 6). The performances of only 13 of the 30 subjects could be described by the generalized matching equation and were within a range of values typical of those reported in the animal literature. Eight subjects showed indifference, 9 undermatched, 7 approximated matching, 3 overmatched, and a further 3 responded exclusively to the richer component of the concurrent schedules. These differing modes of responding were closely related to the different types of performance rules reported by subjects in postexperimental questionnaires. The results are in good agreement with those from studies of human performance on single schedules, suggesting that rule-governed behavior, in interaction with contingencies, may be an important determinant of human choice.     

小学生分数比较中的加工模式:基于反应时和口语报告的研究

选取北京和四川两地53名小学六年级学生分别完成同分子、同分母与异分子异分母三类分数比较任务,收集被试口语报告的策略作为直接证据,并以分数大小和分数距离对反应时的回归分析结果作为间接证据,共同探究被试在分数比较任务中的加工模式,结果发现,（1）在三类分数比较中,被试均采用成分加工模式而非整体加工模式;（2）口语报告的策略与反应时回归分析的结果并不完全吻合,从侧面证明了原有研究方法的不稳定性。     

Communicative development in Swedish children 16-28 months old: the Swedish early communicative development inventory--words and sentences

To describe the development of words and sentences in Swedish children 16-28 months old, 900 parental reports on 336 children were analyzed. Subjects were randomly selected from the national birth register, and there was a response rate of 88%. The assessments were made using the Swedish Early Communicative Development Inventory--words and sentences (SECDI--w&s). Age-based norms for productive vocabulary, pragmatic skills, grammar skills, and maximum length of utterance (MaxLU) were determined. We describe the development of feedback morphemes, semantic categories, and single words and tasks. Correlation across measures was significant, and especially strong between vocabulary size and grammar skills. Optimized positive predictive values were high for 25 to 28 month predictions (71%-88%), and vocabulary scores were found to be of particular predictive importance. No significant gender differences were detected. The clinical relevance of the instrument is discussed.     

When can children handle referential opacity? Evidence for systematic variation in 5- and 6-year-old children's reasoning about beliefs and belief reports

Five- and 6-year-olds (N=51) heard stories in which a character sorted items into two locations. Either the character had a false belief about one of the items (e.g., thought a tin contained biscuits, not Lego), or was only partially informed of an item's dual identity (e.g., did not know that a tie was a present). Children found it easier to reject a report of the character's belief that described the true state of affairs when the character had a false belief (e.g., Is Fred's uncle thinking "where shall I put this Lego?"), than to reject one in which an object known to the character was described using a term of which she was ignorant (e.g., Is Mum thinking "where shall I put this present?"). Similarly, children found it easier to predict the character's incorrect sorting of the target items for false belief (with food not toys) than for dual identity (in the wardrobe not with things to take on a visit). Correct reasoning about beliefs and reports of beliefs that misrepresent an object does not imply mastery of the fact that beliefs represent an object in a particular way.     

The verbalization of multiple strategies in a variant of the traveling salesperson problem

What kinds of strategies do humans employ when confronted with a complex spatial task, and how do they verbalize these strategies? Previous research concerned with the well-known traveling salesperson problem (TSP) typically aimed at the identification of a generally applicable heuristics that adequately represents human behavior in relation to the abstract task of combining points. This paper adopts a novel perspective in two respects. On the one hand, it addresses the strategies people employ when confronted with a more complex task, involving distractors and feature information rather than identical points. On the other hand, retrospective linguistic representations of the strategies used are analyzed in relation to the behavioral data, using discourse analytic methods. Results show that both the behavioral results and the verbalizations point to a range of strategies related to those proposed for solving abstract TSPs. However, in contrast to earlier accounts in the literature, the participants employ a repertory of multi-faceted strategies and planning processes, simplifying and structuring the problem space across subtasks and processes in flexible ways. These findings provide further insight into the nature of human strategies in spatial problem solving tasks and their retrospective verbalization, highlighting how procedures generally known in the literature may be adapted to more complex tasks, and how they may be verbalized spontaneously.