Tactile motion lacks momentum
The displacement of the final position of a moving object in the direction of the observed motion path, i.e. an overestimation, is known as representational momentum. It has been described both in the visual and the auditory domain, and is suggested to be modality-independent. Here, we tested whether a representational momentum can also be demonstrated in the somatosensory domain. While the cognitive literature on representational momentum suggests that it can, previous work on the psychophysics of tactile motion perception would rather predict an underestimation of the perceived endpoint of a tactile stimulus. Tactile motion stimuli were applied on the left and the right dorsal forearms of 32 healthy participants, who were asked to indicate the subjectively perceived endpoint of the stimulation. Velocity, length and direction of the trajectory were varied. Contrary to the prediction based on the representational momentum literature, participants in our experiment significantly displaced the endpoint against the direction of movement (underestimation). The results are thus compatible with previous psychophysical findings on the perception of tactile motion. Further studies combining paradigms from classical psychophysics and cognitive psychology will be needed to resolve the apparently paradoxical predictions by the two literatures.
We thank Stefan Engelter, senior neurologist at University Hospital Basel, for encouraging us to publish this experiment. We thank Peter Rohner for the illustration of the experimental setup and Daniel Goldreich for his comments on a previous version of the manuscript. Finally, the very constructive critique of three expert reviewers is acknowledged.
Compliance with ethical standards
Conflict of interest
All authors declare that they have no conflict of interest.
The study was approved by the local Ethics Committee of the University of Basel. All participants gave written informed consent before the experiment.
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