The Where and How of Touch: A Review of Tactile Localization Research
Tactile localization is the seemingly simple ability to 'tell' where a touch has occurred. However, how this ability is assessed, and what conclusions are drawn from experiments, depends on the theoretical ideas that inspire the research. Here, we review both theoretical frameworks and methodological approaches based on a systematic web-based literature search on tactile localization. After presenting current theories of tactile localization, we discuss task characteristics that differentiate current methodology for tactile localization into at least 8 distinct types of experimental tasks. We describe these tasks, discuss their, often implicit, underlying assumptions and cognitive requirements, and relate them to the theoretical approaches. We then compare, in an exemplary manner, the tactile localization results reported by a subset of studies and demonstrate how some methods are associated with specific biases, illustrating that the choice of experimental method significantly affects the conclusions drawn from the results. Our review suggests that the field currently lacks a clear concept of the specific processes induced by the various experimental tasks and, thus, calls for concerted efforts to clarify and unify currently diverse, fragmented, and partly inconsistent theoretical underpinnings of tactile spatial processing, flanked by dedicated data sharing to allow across-study analysis.