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UBC Theses and Dissertations

Evidence for rapid extraction of numeric information Corbett, E. Jennifer

Abstract

The present study investigated the rapid processing of numeric meaning. Participants compared briefly presented displays of digits, letters, or shapes. Experiment lrevealed three main findings: i . Participants were faster and more accurate when deciding which side of a display had the larger average value (when viewing displays of digits) than when determining which side of a display had the greater occurrence of a target shape (when viewing displays of letters or shapes), suggesting that numeric information was extracted faster and more accurately than information about familiarity or shape; ii. While participants compared digits faster and more accurately than they compared letters or shapes, they compared sideways digits (shapes), letters, and sideways letters (shapes) with equal speed and accuracy, showing a negative effect of sideways rotation for digits but no effect of rotation for letters, suggesting that impairment in performance produced by rotating digits may be attributed to the loss of numeric meaning and not to the loss of familiarity or shape similarities; iii. Participants compared homogeneous displays and single items faster and more accurately than they compared heterogeneous displays across all display types (digits, letters, and shapes), suggesting that the faster and more accurate comparisons of numeric information were not based on the mean value, as found for rapidly extracted geometric properties. Experiment 2 tested the effects of task instructions to compare the average value of digit displays on the rapid extraction of numeric information. It was found that even when participants were told to compare all displays based on the greater occurrence of a target shape, displays of digits were still compared faster and more accurately than displays of familiar letters or simple shapes, suggesting that numeric meaning, not task instructions to compare digits based on average value, was driving the rapid digit comparisons. In Experiment 3, participants were allowed to view the displays of digits, letters, and shapes for as long as they wished. When participants were not under any time constraints imposed by brief stimulus presentations, they compared all display types with similar speed and accuracy, suggesting that they no longer rapidly extracted numeric information when given sufficient time to identify individual stimuli. Taken together, these results support the proposal that the visual system can rapidly represent meaningful (numeric) information when assessing briefly presented visual displays.

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