The importance of response type to the relationship between temporal order and numerical magnitude

Time, number, and space may be represented in the brain by a common set of cognitive/neural mechanisms. In support of this conjecture, Schwarz and Eiselt (Journal of Experimental Psychology: Human Perception and Performance, 35, 989-1004, 2009) found that numerically smaller digits were perceived to occur earlier than larger digits, and they concluded that this difference reflected faster processing of smaller numbers. This difference, however, could have been related to a response bias, whereby participants map responses of "which first" onto the "first" number along the mental number line. In Experiment 1, participants made temporal order judgements between digits presented to the left or to the right. The point of subjective simultaneity was shifted so that the 9 had to be presented before the 2 in order for simultaneity to be perceived. This difference could reflect either faster processing of the 2 or a response bias. Experiments 2a and 2b eliminated response biases by using simultaneity judgements, which have no logical stimulus mapping. Both of the latter experiments established that the 2 was not processed faster than the 9. Although the present results relate specifically to numerical magnitude and temporal order associations, they also have broader implications. Other studies have reported associations between dimensions such as size, duration, and number and have attributed these to parietal mechanisms. Such associations, however, may also be an artefact of response biases.     

Perceptual biases in the horizontal and vertical dimensions are driven by separate cognitive mechanisms

Perceptual attention in healthy participants is characterized by two biases, one operating in the horizontal plane, which draws attention leftward, and the other operating in the vertical plane, which draws attention upward. Given that these biases are reliably found in the same individual, and appear similar at a surface level, a number of researchers have investigated the relationship between horizontal and vertical attentional biases. To date, these investigations have failed to find an association, and this may be due to the fact that one-dimensional vertical and horizontal stimuli were presented separately rather than being measured from a single, two-dimensional stimulus. Across three experiments, two dimensional stimuli were presented, and participants marked the centre of the stimuli. In addition, the shapes of the stimuli were manipulated to determine whether this produced the same modulation of the two biases. Across 13 stimuli and three experiments there were no correlations between the vertical and horizontal biases. In addition, manipulations of stimulus shape, which affected biases in one dimension, did not affect biases in the other dimension. There were, however, consistent correlations between the degree of bias within each dimension across the different stimuli. This study has produced converging evidence that horizontal and vertical biases in spatial judgments rely on separate cognitive mechanisms. To account for these results we discuss a model whereby horizontal asymmetries rely more on space-based mechanisms whereas vertical asymmetries rely more on object-based mechanisms.     

Near, yet so far: the effect of pictorial cues on spatial attention

Distinct cognitive and neural mechanisms underlie perception and action in near (within-reach) and far (outside-reach) space. Objects in far space can be brought into the brain's near-space through tool-use. We determined whether a near object can be pushed into far space by changing the pictorial context in which it occurs. Participants (n = 372) made relative length judgements for lines presented in near space, but superimposed over photographs of near and far objects. The left segment of the line was overestimated in the baseline and near-context conditions whereas the right was overestimated in the far-context. The change from leftward to rightward overestimation is the same when lines are physically shifted from near to far space. Because participants did not have to do anything in relation to the photograph, the results suggest that simply viewing images with a near/far context can cause a shift of attention along the distal/proximal axis, which may reflect differential activation of the ventral/dorsal visual streams.     

Unstable world: Recent experience affects spatial perception

Psychonomic Bulletin & Review - An accurate perception of the space surrounding us is central for effective and safe everyday functioning. Understanding the factors influencing spatial...