The estimation of variance-covariance and correlation matrices from incomplete data

Employing simulated data, several methods for estimating correlation and variance-covariance matrices are studied for observations missing at random from data matrices. The effect of sample size, number of variables, percent of missing data and average intercorrelations of variables are examined for several proposed methods.The author is indebted to Professors Leonard A. Marascuilo, Gus W. Haggstrom, especially Henry F. Kaiser for their invaluable suggestions throughout this work. Appreciation is also extended to the Computer Center facility of the University of California at Berkeley for the use of computer time to complete the necessary computations.     

Effects of peer social initiations on the behavior of withdrawn preschool children

Social approach to peers was evaluated as an intervention for isolate preschoolers. During baseline, confederate peers made few social approaches to the target subjects. Confederates greatly increased their rate of social approaches during the first intervention, decreased social approaches during a second baseline, and increased social approaches again in a second intervention phase. Increases in confederate social initiations immediately increased the frequency of subjects' positive social behavior. Additionally, five of six subjects showed an increase in their own positive social initiations during intervention periods. The results suggest that: (a) peers may be programmed to increase the positive social behaviors of their isolate classmates, and (b) remediating social deficits requires assessment and intervention specifically tailored to the individual child.     

Is temporal spacing of tests helpful even when it inflates error rates?

The occurrence of errors is often thought to impede associative learning. This was tested in 2 studies, each of which involved 2 sessions. In Session 1, subjects learned foreign vocabulary (Experiment 1) or obscure English words (Experiment 2) and received 2 tests (each with corrective feedback) separated by a variable lag. Greater lags drastically reduced performance on the 2nd test. However, they dramatically improved performance in a Session-2 test given 1 day (Experiment 1) or 1 week later (Experiment 2). This pattern held even for items that elicited errors on the 1st test of Day 1. Evidently, the benefit of spacing overwhelms any possible harmful effect of producing errors. The results have clear and nonobvious implications for computer-aided instruction.     

Rescher's Metaphilosophy

Books reviewed in this article:
Nicholas Rescher, Philosophical Standardism
Nicholas Rescher, The Strife of Systems
Nicholas Rescher, A System of Pragmatic Idealism. Vol. III, Metaphysical Inquiries     

Does “Violent” Mean “Bad”? Individual Definitions of Violence

People use the word “violent” to describe a wide range of behaviors. When referring to acts of force, however, past research indicates that people often reserve the word “violent” to refer to acts of force that they define as “bad.” In the current study we use vignettes to explore variation in people’s definitions of a particular instance of the use of force. The findings indicate support for the idea that people reserve the word “violent” to refer to acts of force they view as “bad.” Findings indicate there is variation in perceptions of the level of violence, and whether the incident was even violent. Characteristics of the incident as well as the gender of those involved account for the majority of the variance explained.     

The role of retrieval mode and retrieval orientation in retrieval practice: insights from comparing recognition memory testing formats and restudying

The effectiveness of retrieval practice for aiding long-term memory, referred to as the testing effect, has been widely demonstrated. However, the specific neurocognitive mechanisms underlying this phenomenon remain unclear. In the present study, we sought to explore the role of pre-retrieval processes at initial testing on later recognition performance by using event-related potentials (ERPs). Subjects studied two lists of words (Chinese characters) and then performed a recognition task or a source memory task, or restudied the word lists. At the end of the experiment, subjects received a final recognition test based on the remember–know paradigm. Behaviorally, initial testing (active retrieval) enhanced memory retention relative to restudying (passive retrieval). The retrieval mode at initial testing was indexed by more positive-going ERPs for unstudied items in the active-retrieval tasks than in passive retrieval from 300 to 900 ms. Follow-up analyses showed that the magnitude of the early ERP retrieval mode effect (300–500 ms) was predictive of the behavioral testing effect later on. In addition, the ERPs for correctly rejected new items during initial testing differed between the two active-retrieval tasks from 500 to 900 ms, and this ERP retrieval orientation effect predicted differential behavioral testing gains between the two active-retrieval conditions. Our findings confirm that initial testing promotes later retrieval relative to restudying, and they further suggest that adopting pre-retrieval processing in the forms of retrieval mode and retrieval orientation might contribute to these memory enhancements.     

Wittgenstein's ab-Notation: An Iconic Proof Procedure

This paper systematically outlines Wittgenstein's ab-notation. The purpose of this notation is to provide a proof procedure in which ordinary logical formulas are converted into ideal symbols that identify the logical properties of the initial formulas. The general ideas underlying this procedure are in opposition to a traditional conception of axiomatic proof and are related to Peirce's iconic logic. Based on Wittgenstein's scanty remarks concerning his ab-notation, which almost all apply to propositional logic, this paper explains how to extend his method to a subset of first-order formulas, namely, formulas that do not contain dyadic sentential connectives within the scope of any quantifier.     

Underdetermination and provability: a reply to Olaf Müller

Newton claims to have proven the heterogeneity of light through his experimentum crucis. However, Olaf Müller has worked out in detail Goethe’s idea that one could likewise prove the heterogeneity of darkness by inverting Newton’s famous experiment. Müller concludes that this invalidates Newton’s claim of proof. Yet this conclusion only holds if the heterogeneity of light and the heterogeneity of darkness is logically incompatible. This paper shows that this is not the case. Instead, in Quine’s terms, we have two logically compatible theories based on mutually irreducible theoretical terms. From a Quinean point of view, this does no harm to the provability of the corresponding statements.