Master of Science
Humans perceive ratios for different spatial magnitudes such as length, area, and numerosity, and temporal magnitudes such as duration. Previous studies have shown that spatial ratios may be processed by a common ratio processing system. The aim of the current study was to determine whether ratios across spatial and temporal domains may also be processed by a common system. Two hundred and seventy-five participants completed a series of spatial and temporal ratio estimation and magnitude discrimination tasks. Structural equation modeling (SEM) was used to analyze the relationship between ratio processing across domains when controlling for absolute magnitude processing ability. Results showed a significant relationship between spatial and temporal ratio processing. Absolute magnitude processing was also shown to explain a large part of the variance in both spatial and temporal ratio processing factors. These results have implications for theories of general magnitude processing for both absolute and relative magnitudes.
Summary for Lay Audience
Imagine a basket containing two green apples and two red apples. Now imagine another basket containing five green apples and five red apples. Although the total number of apples was different between the two baskets, you probably noticed that the proportion of red and green apples was the same. In both baskets, half of the apples are green while the other half are red. This ability to perceive relationships between quantities is called ratio processing. Interestingly, ratio processing can be done for different types of magnitudes like number, length, area and duration. The aim of the current study was to examine whether spatial and temporal ratios are processing by a general ratio processing mechanism. Two types of tasks were used: ratio estimation tasks, which measured ratio processing abilities, and magnitude discrimination, which measured absolute magnitude processing abilities. In ratio estimation tasks, participants were presented a ratio and asked to represent that ratio on a line. In magnitude discrimination tasks, participants were presented two magnitudes (e.g., two lengths) and asked which of the two magnitudes was the largest. Both types of tasks were done with length, area, numerosity (i.e., number of dots) and duration. Using structural equation modeling, performance on spatial ratio estimation tasks were correlated with performance on temporal ratio estimation tasks while controlling for participant’s performance on the magnitude discrimination tasks. Our results showed a significant relation between people’s performance on spatial and temporal ratio estimation tasks. This indicates that spatial and temporal ratios may be processed by a common ratio processing system (RPS; Lewis, Matthews, & Hubbard, 2015). Additionally, participants’ ability to discriminate absolute magnitudes explained a large part of their performance on ratio estimation tasks. This suggests that, even though participants’ performance on ratio estimation tasks can in part be explained by a shared ratio processing mechanism across domains related, another part is also largely explained by absolute magnitude mechanisms associated with either the spatial and/or temporal domain.
Lagace-Cusiac, Rebekka, "A Sense of Proportion: How humans process relative magnitudes in space and time" (2021). Electronic Thesis and Dissertation Repository. 8039.
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