The intensity order illusion: temporal order of different vibrotactile intensity causes systematic localization errors

Abstract

Haptic illusions serve as important tools for studying neurocognitive processing of touch and can be utilized in practical contexts. We report a new spatiotemporal haptic illusion that involves mislocalization when the order of vibrotactile intensity is manipulated. We tested two types of motors mounted in a 4 × 4 array in the lower thoracic region. We created apparent movement with two successive vibrotactile stimulations of varying distance (40, 20, or 0 mm) and direction (up, down, or same) while changing the temporal order of stimulation intensity (strong-weak vs. weak-strong). Participants judged the perceived direction of movement in a 2-alternative forced-choice task. The results suggest that varying the temporal order of vibrotactile stimuli with different intensity leads to systematic localization errors: when a strong-intensity stimulus was followed by a weak-intensity stimulus, the probability that participants perceived a downward movement increased, and vice versa. The illusion is so strong that the order of the strength of stimulation determined perception even when the actual presentation movement was the opposite. We then verified this “intensity order illusion” using an open response format where observers judged the orientation of an imaginary line drawn between two sequential tactor activations. The intensity order illusion reveals a strong bias in vibrotactile perception that has strong implications for the design of haptic information systems. NEW & NOTEWORTHY We report a new illusion involving mislocalization of stimulation when the order of vibrotactile intensity is manipulated. When a strong-intensity stimulus follows a weak-intensity stimulus, the probability that participants perceive an upward movement increases, and vice versa. The illusion is so strong that the order of the strength of stimulation determined perception even when the actual presentation movement was the opposite. This illusion is important for the design of vibrotactile stimulation displays.

Perception of Tactile Distance on the Back

“…, 'oblique' effects in which judgments or orientation are biased to the horizontal and vertical axes (Kappers, Bay, & Plaisier, 2020;Novich & Eagleman, 2015), and interactions between stimulus intensity and perceived direction of tactile apparent motion (Hoffmann, Brinkhuis, Unnthorsson, & Kristjánsson, 2019). There is some evidence, however, that anisotropy on the back may be different from the limbs.…”

“…Despite having relatively poor tactile sensitivity (Mancini et al, 2014;Weinstein, 1968), the back has been the focus of a substantial amount of research due in large part to its use as a surface for sensorysubstitution devices (Bach-y-Rita et al, 1969;Kristja´nsson et al, 2016). Various systematic misperceptions of touch on the back have been reported, such as biases towards landmarks such as the spine (Cholewiak et al, 2004;van Erp, 2005), "oblique" effects in which judgements or orientation are biased to the horizontal and vertical axes (Kappers et al, 2020;Novich & Eagleman, 2015), and interactions between stimulus intensity and perceived direction of tactile apparent motion (Hoffmann et al, 2019). There is some evidence, however, that anisotropy on the back may be different from the limbs.…”

Palpation of the lateral bands of the extensor apparatus of the fingers. Anatomy of a neglected clinical finding

“…The third finding of interest was the meager forward displacement of the LB by US compared with palpation. This difference could result from a haptic illusion of movement (Hoffmann et al, 2019). Because active MCP extension tenses the ET and PIP flexion tenses the LBs, being both structures linked by the DA, palpation during repeated PIP flexion and extension may create an illusion of displacement as the tensile load sequentially shifts from dorsal to palmar and vice versa.…”

Tactile temporal offset cues reduce visual representational momentum

“…Moreover, switching attention from or to the tactile modality is more costly than switching from the auditory or visual modality (e.g., Spence et al, 2001a). Additionally, recent evidence indicates that tactile perception is different for different tactile stimulation types (e.g., electrocutaneous, vibrotactile, air puffs, touching; Hoffmann et al, 2018;Hoffmann et al, 2019), opening up the possibility that a different tactile set-up might have resulted in a different interaction between the two stimuli. Yet, if at all, and how exactly, another vibrotactile set-up might have resulted in a different data pattern is an open question to this point.…”