The judgment operation of ratio production

The judgment operation that individuals perform when they set a sensory intensity in a predefined ratio to a standard sensory intensity is unknown. The present study was conducted to determine this operation by functional measurement. Participants first produced a sensory intensity for each combination of various predefined ratios and standard sensory intensities. Subsequently, they rated these produced intensities. Factorial graphs derived from these ratings were essentially parallel. This result shows that participants produced each sensory intensity by operating as if they were adding an amount of sensory intensity to the respective standard sensory intensity. It was found that this added amount varied nonlinearly with the predefined ratio, implying that ratio productions are nonlinear.     

An experimental comparison of three- versus four-surface phenomenal transparency

The three-surface transparency occurs when an object seen through a transparency does not jut out under the transparent surface. The four-surface transparency occurs when the object juts out. Observers rated the density of the transparent surface in both kinds of transparency. The results seem to show that the topological diversity between the two kinds of transparency has no functional significance. The stimulus conditions ruling the generation of judgments were detected and expressed in terms of an algebraic model.     

An experimental check on Stevens’s explanation of the partition paradox by successive doubling and bisecting

Scaling methods based on direct estimation of sensory ratios and intervals give discrepant results (the partition paradox). Stevens’s explanation of this discrepancy was tested here. Given a psychological magnitude, ψ, observers were required to select a magnitude 2ψ, and subsequently to bisect the interval between ψ and 2ψ. Stevens’s hypothesis predicts that the bisected psychological magnitude falls between 1.41ψ and 1.50ψ. The hypothesis is not substantiated, since a bisected magnitude of 1.55ψ was obtained. Furthermore, observers had to bisect the interval between ψ and an imagined magnitude of 2ψ. The results show that observers are able to producereliably both a visual and a representational double.     

The effects of imagery instructions on total congenital blind recall

Abstract

Research on the performance of total congenital blind subjects in imagery tasks is of particular interest because it helps to evaluate the consequences of their lack of visual experience. The present paper examines some points which remained unclear in the preceding research on the effects of imagery instructions on the recall of blind subjects. In Experiment 1 it is shown that, in a free recall task of unrelated nouns, the blind may take advantage of imagery instructions, independently of the particular requirement to form either common or bizarre images. In Experiment 2 the multiple image processing deficit of the blind found by De Beni and Cornoldi (1988) was again observed, but the effect was not found when the same quantity of material had to be processed verbally. Results are interpreted as showing that, although the blind may follow imagery instructions, their visual handicap creates specific difficulties in creating interactive images involving several items at the same time.     

Test of models of achromatic transparency

Consider an achromatic disk transparent on an achromatic background formed by two adjoining rectangles, with the common border of the rectangles dividing the disk in half. Current models of achromatic transparency contend that the perceived extent of transparency of the disk depends on the luminance contrast inside the disk and on the luminance contrast in the background outside the disk. Here, a model is proposed which contends that this perceived extent is determined only by the luminance contrasts inherent in the disk: inside the disk and between the disk and the background. Two experiments were designed to determine which luminance contrasts influence transparency. In the first experiment, subjects rated the perceived extent of transparency of the disk for different combinations of the luminances of the disk and of the background. The results strengthen the view that the perceived extent of transparency depends on the luminance contrasts inherent in the disk. In the second experiment, a test was made of the possibility that luminance contrasts between adjoining areas of the background outside the disk are nonessential for transparency. The results show that transparency occurred both when the areas of the background outside the transparent region adjoined one another and when they were separated, confirming that the perceived extent of transparency depended only on luminance contrasts between adjoining areas inherent in the disk.     

Visual but not spatial working memory deficit in children with spina bifida

Twenty children with spina bifida and twenty controls were assessed on a battery of visuospatial working memory tests. Children with spina bifida performed as well as the control group in the visuospatial test and in the forward and backward versions of the Corsi test, but were impaired in the 'House Visual Span.' This test, designed in our lab, provides specific information regarding visual ability to discriminate between pictorial targets and lures, and requires specific visual processing of stimuli. These results are discussed in terms of working memory models and are viewed as supporting the distinction between the visual and spatial components of working memory.