Visual imagery and evoked-responses

Summary Two experiments were performed to determine whether a physiological correlate of visual imagery could be measured from visually-evoked-responses (VERs). High and Low imagery groups were used. There was no direct effect of imagery, although some differences between the groups emerged. These differences are thought to be due to factors associated with imaging, but not imagery per se.     

CULTURAL VARIATION IN PROBABILISTIC THINKING: ALTERNATIVE WAYS OF DEALING WITH UNCERTAINTY*

This study reviews research on cultural differences in “probabilistic thinking” and presents some intra- and inter-cultural findings. Strong differences are shown to exist between people raised under Asian and British cultures on measures of this ability. These differences were found to out-weigh any influence of subculture, religion, occupation, arts/science orientation and sex. Generally, Asians were found to adopt a less finely differentiated view of uncertainty both numerically and verbally than did the British sample. Numerical probabilities assessed by the Asians were more extreme and less realistic than those assessed by the British sample. Possible antecedents of these differences are outlined, and cultural differences in probabilistic thinking are shown to be compatible with decriptions of cultural differences in business decision making. It is argued that there are qualitative cultural differences in ways of dealing with uncertainty.     

Functional Differences Between Upright and Rotated Images

In Experiment I subjects imaged an alphanumeric character either upright or upside-down, and triggered a test display character. Their task was to decide as quickly as possible whether the test character was NORMAL or MIRRORED. On 72% of the trials the test was at the orientation imaged. Reaction time (RT) was then about 200 ms longer in the upside-down image condition. This difference reduced with practice. On the remaining trials the orientation of the test character differed from that of the prepared image. For upright images RT increased monotonically with the angular difference in orientation between test and image. For upside-down images RT did not increase monotonically with angular difference as there was a wide dip around the upright. Further experiments suggested that upside-down images can be rotated, but at considerably slower rates than upright ones, and that the apparent rates of rotation for upside-down images are dependent upon the width of the sector tested. These results indicate that visual short-term memory (STM) and long-term memory (LTM) are distinct; that the process of mental rotation does not operate directly upon LTM; and that functionally, upright and rotated images may differ in important ways.     

Parafoveal word perception: A case against semantic preprocessing

The present experiment investigated semantic information extraction in parafoveal word perception. An ambiguous word (bank) was presented in foveal vision, and simultaneously a disambiguating word (water, money) was presented in the parafovea. Subjects were required to make a forced choice between two phrases, and the task was constructed so that a correct choice could be made if semantic information about both the foveal and parafoveal word had been obtained. However, the results indicated that the forced-choice results could be explained by two factors: identification of the parafoveal word and correct guessing. Hence, it was concluded that those models of reading which rely on unconscious semantic preprocessing of parafoveal words were not supported.     

Proportionality,linearity, and parameter constancy: Messick and Sentis reconsidered

Messick and Sentis found greater support for weak proportionality in subjects' outcome allocations (suggesting that subjects wish to maintain a constant ratio between outcomes across situations when inputs are held constant) than for constant differences between outcomes. They claimed that their data thus provided stronger support for Adams' ratio definition of equity than for Harris' linear formula. A dialogue between the two sets of authors establishes that (1) so far as their specification of fair outcomes is concerned, Adams' formula is a special case of the linear formula; (2) weak proportionality does not necessarily follow from Adams' formula and can be derived from the linear formula; (3) Adams' formula applied to subjective (rather than experimenter-defined) inputs nevertheless provides a more natural base from which to derive weak proportionality than does the linear formula in its general form; (4) excellent fits to several sets of data, including much better fit to Messick and Sentis' data than that provided by weak proportionality, are obtained if we assume that subjects use allocations which are a weighted average of those implied by Adams' formula, the Equality principle, and Komorita and Kravitz' Equal Excess Norm; and (5) a fit to Messick and Sentis' data that is almost as good as that provided by the weighted solutions model is obtained by assuming that subjects apply Adams' formula to subjective inputs and subjective outcomes that are different from the corresponding experimenter-defined values. It is agreed that the delineation of the relationships among observable properties of outcome distributions, alternative equity formulae, and different psychological processes is as important as it can be devious.     

Asymmetries in the perceptual span for Israeli readers

Native Israeli readers read Hebrew and English text as their eye movements were monitored. A window of text moved in synchrony with their eye movements and the window was either symmetrical about the fixation point or offset to the left or right. When subjects were reading Hebrew, the perceptual span was asymmetric to the left and when they were reading English it was asymmetric to the right. The results point out the importance of attentional factors in reading.     

Is visual information integrated across saccades?

After subjects established fixation on a target cross, 12 dots were presented parafoveally. When the dots were presented, the subjects made an eye movement to the location of the dots, and during the saccade the 12 initially presented dots were replaced by 12 other dots. The 24 dots were part of a 5 × 5 matrix, and the task of the subject was to report which dot was missing. The data were consistent with other recent studies: subjects could successfully report the location of the missing dot far above chance (54%), whereas performance in a control condition (in which the two sets of dots were presented to different spatial and retinal locations) was almost at chance level (10%). However, a number of control conditions demonstrated that the effect was due primarily to persistence from the phosphor of the cathode ray tube used for stimulus presentation and that little of the visual information integrated was across two fixations. Implications of the results for a theory of integration across saccades are discussed.