Lotus 1-2-3 simulation of frequency encoding on the basilar membrane

A spreadsheet simulation was designed to describe frequency encoding on the basilar membrane according to the place theory (Greenwood, 1961). For any given frequency, the simulation displayed the location of maximum amplitude on the basilar membrane and the relevant critical bandwidth. The authors found a very high correlation between data given by the simulation and data from empirical research. The high correlation indicates the validity of the place theory of frequency encoding and the usefulness of this simulation for future research purposes.     

Practices and representations of child care and motor development among West Africans in Paris

Massage techniques and postural manipulation used by West African women immigrants in Paris were studied, with the aim of demonstrating that culturally regulated caretaking practices have an influence on infant motor development. Twenty-five infants were observed between the ages of 3 and 12 months and 9 and 15 months. Frequency of massage and its accompanying set of physical exercises were found to be related to age at onset of independent walking. The findings show that infants receiving daily massage walk significantly earlier than infants who do not receive massage, thus confirming other reports that vestibular and postural stimulation have a positive effect on motor development. These results are discussed in relation to the observed frequencey of contact and of physical games with the caregiver for a smaller sample of three infants, and to parental expectations about the age of acquisition of certain cognitive and motor abilities. African immigrant mothers expect their infants to sit and to walk earlier than French mothers. The conclusion emphasizes the contribution of social anthropology, which shows that in all cultures, physical development and body changes elicit symbolic practices and a search for explanation.     

An X Windows tool for synthesizing face images from eigenvectors

An X Windows software tool for the construction of faces with a weighted combination of eigenvectors is described. The eigenvectors were extracted from an autoassociative matrix that comprised 100 face images. The program input consists of eigenvectors and sets of weights that describe individual faces and combines these to create face images. The tool creates a panel of buttons that permits the display of individual eigenvectors and the display of an average face as well. Facilities for on-line changes to the intensity of individual eigenvectors can be used to change the appearance of a face. Previously, O’Toole, Abdi, Deffenbacher, and Bartlett (1991) have shown that the intensity of certain individual eigenvectors contains reliable information for determining the sex and race of the face.     

Evaluating student achievement with a relational database

Commercial database programs such as dBase and Paradox, although developed originally for business applications, are versatile and powerful tools that can be used for an academic purpose such as evaluating student performance. They can be used to write and store test questions, assemble and print classroom or on-line laboratory tests, and calculate grades, test statistics, and so forth. Databases are flexible, unlike textbook “ancillary” test bank programs that are inextricably bound to the strictly linear format and brief shelf life of specific textbook editions. A prototypical relational database program is described, with which an instructor can produce tests based on generic terms adapted from Boneau’s (1990) study of psychological literacy, as well as on behavioral learning objectives adapted from Bloom’s (1956) taxonomy of educational objectives. As a relational database, the program integrates terms, objectives, questions, tests, and test scores, and avoids unnecessary data duplication and waste of computer storage space.     

Perceived numerosity of spatiotemporal events

Numerosity discrimination was examined when items were varied in space-time position rather than in space only. Observers were instructed to indicate which of two adjacent streamsof visual events contained more items. The precision of numerosity discrimination of dynamic events was not remarkably different from that of static patterns. Two basic numerosity biases previously found for static dot patterns—inhibitory overestimation and satellite underestimation—were demonstrated for items distributed randomly over a spatiotemporal interval. It was also demonstrated that two streams, equated in the number and luminous energy of items, are not judged equal in their visible number if items in one of these two streams have longer duration than items in the second stream. These findings can be accounted for by the occupancy model of perceived numerosity (Allik & Tuulmets, 1991a) if it is supposed that the impact that each element has on its neighborhood is spread along both spatial and temporal coordinates. Perceived numerosity decreases with both spatial and temporal proximity between the-visual-items. Space and time have interchangeable effects on perceived numerosity: the amount of numerosity bias caused by the spatial proximity of items can also be produced by the properly chosen temporal proximity of items     

Shape from stereo: A systematic approach using quadratic surfaces

We used quadratic shapes in several psychophysical shape-from-stereo tasks. The shapes were elegantly represented in a 2-D parameter space by the scale-independentshape index and the scale-dependentcurvedness. Using random-dot stereograms to depict the surfaces, we found that the shape of hyperbolic surfaces is slightly more difficult to recognize than the shape of elliptic surfaces. We found that curvedness (and indirectly, scale) has little or no influence on shape recognition.     

Hemispheric differences in the interference among components of compound gratings

The relationship between local/global and high/low spatial-frequency processing in hemispheric asymmetries was explored. Subjects were required to judge the orientation of a high- or low-spatial-frequency component of a compound grating presented in the left visual field (LVF) or right visual field (RVF). In Experiment 1, attention was focused on one or the other component. A signal detection analysis indicated that sensitivity (d′) to the high-spatial-frequency target was reduced more by the presence of the low-spatial-frequency component when both were presented in the LVF rather than in the RVF. In Experiment 2, subjects determined whether a target orientation was present, independent of spatial frequency at only a single level (i.e., at the high- or low-spatial-frequency level), as opposed to both or neither level. An RVF/LH (left hemisphere) advantage was found when the decision was based on the orientation of the high-frequency component. The asymmetrical influence of visual field of presentation and spatial frequency upon sensitivity is discussed in terms of hemispheric differences in the magnitude of inhibition between spatial-frequency channels and in the role of transient channel activity to capture and direct higher order attentional processes.     

Additivity of loudness across critical bands: A critical test

The use of magnitude estimation as well as axiomatic measurement theory has led to the suggestion that loudness adds across critical bands. In the present paper, we challenge this postulate by applying a more sensitive methodology, based on Falmagne’s (1976) random conjoint measurement procedure. A necessary condition for additivity of loudness was investigated in tone complexes consisting of 2-kHz and 5-kHz (resp. 3-kHz) components; the results showed systematic deviations from additivity. We argue that these deviations are due to asymmetric masking of the higher component by the lower one, and we propose a tentative quantitative model to account for the data. Such a model is in line with results from tone-on-tone masking, which show masking to be effective over a range of several critical bands.