Abstract
The human brain uses perceptual information to create a correct representation of the external world. Converging data indicate that the perceptual processing of, space, and quantities frequently is based on a shared mental magnitude system, where low and high quantities are represented in the left and right space, respectively. The present study explores how the magnitude affects spatial representation in the tactile modality. We investigated these processes using stimulus-response (S-R) compatibility tasks (i.e., sensorimotor tasks that present an association/dissociation between the perception of a stimulus and the required action, generally increasing/decreasing accuracy and decreasing/increasing reaction times of the subject). In our study, the participant performed a discrimination task between high- and low-frequency vibrotactile stimuli, regardless of the stimulation’s spatial position. When the response code was incompatible with the mental magnitude line (i.e., left button for high-frequency and right button for low-frequency responses), we found that the participants bypassed the spatial congruence, showing a magnitude S-R compatibility effect. We called this phenomenon the Spatial–Tactile Association of Response Codes (STARC) effect. Moreover, we observed that the internal frame of reference embodies the STARC effect. Indeed, the participants’ performance reversed between uncrossed- and crossed-hands posture, suggesting that spatial reference frames play a role in the process of expressing mental magnitude, at least in terms of the tactile modality.
Highlights
To interact with the environment, we must plan and execute actions following sensory inputs and their spatial representations
This study firstly aimed to investigate the effect of the mental magnitude line on a tactile S-R compatibility task
We demonstrated in tactile modality, for the first, the presence of a magnitude-congruency effect on horizontal response position and that the mental magnitude effects itself can overcome spatial S-R compatibility
Summary
To interact with the environment, we must plan and execute actions following sensory inputs and their spatial representations. Behavioral performance is better when the stimulus (sensory input) and the response (action) share common spatial features; even these features are task irrelevant. There has been work regarding influence on the horizontal space in S-R compatibility, and how different features become affected These studies found that numbers are represented in a left-to-right fashion, as in the SNARC effect, and auditory pitch [SMARC effect (Rusconi et al, 2006)], time [STEARC effect (Ishihara et al, 2008)], linguistic markedness, [MARC effect (Nuerk et al, 2004)], size (Ren et al, 2011; Wühr and Seegelke, 2018), and quantity [SQUARC effect A number of studies have demonstrated magnitude S-R compatibility effects on continue and discrete quantities in both auditory and visual domains (for a recent review, see Macnamara et al, 2018)
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