Normative location theory: Placement in continuous space

This paper selectively reviews an area of operations research, refered to as normative location theory, that deals with the placement of objects in continuous space. The computational procedures discussed in this literature require initially that a certain set objects be located a priori; the placement of the objects in a second set is then determined in such a way that the total “interaction” among the fixed and variable objects is minimized. A number of strategies appropriate for different distance functions are surveyed and a numerical example is given illustrating one particular iterative algorithm. Although the current versions of these location methods depend upon more than the nonmetric information contained in the proximity measures defined for all pairs of objects, they can be generalized, and consequently, several possible connections to nonmetric multidimensional scaling are pointed out.     

Variation in test validity with variation in the distribution of item difficulties,number of items,and degree of their intercorrelation

The relation between item difficulty distributions and the validity and reliability of tests is computed through use of normal correlation surfaces for varying numbers of items and varying degrees of item intercorrelations. Optimal or near optimal item difficulty distributions are thus identified for various possible item difficulty distributions. The results indicate that, if a test is of conventional length, is homogeneous as to content, and has a symmetrical distribution of item difficulties, correlation with a normally distributed perfect measure of the attribute common to the items does not vary appreciably with variation in the item difficulty distribution. Greater variation was evident in correlation with a second duplicate test (reliability). The general implications of these findings and their particular significance for evaluating techniques aimed at increasing reliability are considered.     

Altered states of consciousness, dissociation, and dream recall

In a sample of 71 medical students, dream recall frequency was positively correlated with proneness to altered states of consciousness (r = .26) measured by the State of Mind and Consciousness Questionnaire and dissociation (r = .29) measured by the Dissociative Experiences Scale II. A regression analysis, however, yielded neither altered states of consciousness nor dissociation, sex, or age to be significant predictors of dream recall frequency. Among women dream recall frequency was associated with proneness to dissociation; among men it was correlated with proneness to altered states of consciousness.     

Spatio-temporal working-memory and short-term object-location tasks use different memory mechanisms

Spatial short-term memory for objects' locations was investigated in a spatial relocation task. During maintenance, dynamic visual noise or spatial tapping were administered as visual or spatial secondary tasks, respectively. Because memory for location should tap the visual component of working memory, a visual but not a spatial secondary task should impair location memory. In fact, neither of the tasks impaired memory (Experiment 1), although the expected dissociation between visual and spatial components was clearly confirmed for a spatio-temporal main task (Corsi test) (Experiment 2). We then contrasted location memory for pictures of objects and of nonsense figures under visual interference. Real objects were relocated much better than nonsense figures, and visual noise was again ineffective (Experiment 3). When spatial tapping was combined with the same material (Experiment 3a), again no influence on memory for locations of objects was observed and only a small influence on remembering nonsense figures. We suggest that the Corsi and the relocation VSWM-tasks use different memory mechanisms. The configuration of objects is reconstructed from perceptual records in an episodic buffer, provided by the same structures that enable visual memory after longer intervals. Rehearsal is not necessary for the persistence of these traces. In contrast, in the Corsi task remembering, a temporal sequence across homogeneous locations needs spatio-temporal marking and therefore active rehearsal of the locations by shifting spatial attention. A spatially demanding secondary task during retention interrupts this rehearsal.     

Time-to-contact estimation of accelerated stimuli is based on first-order information

The goal of this study was to test whether 1st-order information, which does not account for acceleration, is used (a) to estimate the time to contact (TTC) of an accelerated stimulus after the occlusion of a final part of its trajectory and (b) to indirectly intercept an accelerated stimulus with a thrown projectile. Both tasks require the production of an action on the basis of predictive information acquired before the arrival of the stimulus at the target and allow the experimenter to make quantitative predictions about the participants' use (or nonuse) of 1st-order information. The results show that participants do not use information about acceleration and that they commit errors that rely quantitatively on 1st-order information even when acceleration is psychophysically detectable. In the indirect interceptive task, action is planned about 200 ms before the initiation of the movement, at which time the 1st-order TTC attains a critical value.     

MMPI-2 and MCMI-III scores among dutch inpatient substance abusers: Assessing correspondence and cross-cultural equivalence

The Millon Clinical Multiaxial Inventory (MCMI-II and MCMI-III) and the Minnesota Multiphasic Personality Inventory (MMPI-2) were applied to 263 Dutch inpatient substance abusers with multiple psychiatric diagnoses, and the results compared with those of 306 North-American substance abusers studied by Ward (1995). We looked for structural similarity both across groups (per instrument) and across the two instruments (per sample), using principal components analysis and congruence analysis. The component structure found by Ward was partly replicated in the Dutch group, thus cross-validating the use of the two instruments with these patients. Moreover, as found by Ward, the MMPI-2 content and supplementary scales of the Dutch sample proved to be important determinants of the first three MMPI-2 components, adding to convergent validity. Questions remained about the influence of the (dis)continuity of MCMI-II and MCMI-III on the replicability of the MCMI components.     

Signing enhances memory like performing actions

In three experiments, we investigated the influence of the overt performance of signs on memory. Deaf and hearing participants studied lists of action phrases (Experiment 1) or nouns (Experiment 2) under standard verbal instruction, under the instructions to sign the verbal phrase, to symbolically perform the denoted action, or to carry out a prototypical action corresponding to each noun. Higher recall and recognition performances were observed when actions were performed than in the verbal encoding condition, and signing was as effective for memory as was enactment. Thus, overt signing can induce an enactment effect. In contrast, Experiment 3 demonstrated that performing an unrelated action did not. A unique but unrelated action was not memory efficient.     

Effects of Individual Differences on Applicant Perceptions of an Operational Assessment Center

Knowing to what extent applicant reactions are related to stable individual differences and not only to characteristics of a selection procedure is important for the design and administration of the selection procedure and for dealing with applicants. The aim of this study was to explore relationships between individual differences (Big Five, core self‐evaluations, trait affectivity, and general mental ability) and applicants' perceptions of an operational assessment center (AC). Data from 294 applicants revealed that individual difference variables explained significant variance in their perceptions of the AC, even after controlling for self‐rated and actual performance. Based on these results, the nature of the applicant pool should be considered for designing selection procedures, dealing with applicants, and for research purposes.