From a recently published scientific paper from the journal Transactions on Computer-Human Interaction titled "TickleFoot: Design, Development and Evaluation of a Novel Foot-Tickling Mechanism That Can Evoke Laughter" —
Tickling is a type of sensation that is associated with laughter, smiling, or other similar reactions. Psychology research has shown that tickling and laughter can significantly relieve stress. Although several tickling artifacts have been suggested in prior work, limited knowledge is available if those artifacts could evoke laughter. In this article, we aim at filling this gap by designing and developing a novel foot-tickling mechanism that can evoke laughter. We first developed an actuator that can create tickling sensations along the sole of the foot utilising magnet-driven brushes. Then, we conducted two studies to identify the most ticklish locations of the foot's sole and stimulation patterns that can evoke laughter. In a follow-up study with a new set of participants, we confirmed that the identified stimuli could evoke laughter. From the participants' feedback, we derived several applications that such a simulation could be useful. Finally, we embedded our actuators into a flexible insole, demonstrating the potential of a wearable tickling insole.
More on the study, from New Scientist:
The team conducted a study with 13 participants, seven women and six men, who rated the level of ticklishness they felt on a seven-point scale as a single brush was moved to different locations.
The average value given by women was 5.57, higher than the average of 3.83 from men, and there were also slight gender differences regarding the most ticklish spots on the foot; for women the highest score was given for the centre of the arch, while for men the most ticklish place was slightly closer to the toes.
The TickleFoot device, which is powered by lithium-ion batteries that last for 60 minutes of tickling, can be turned on and off remotely.
This is so much more sinister than Skynet.
TickleFoot: Design, Development and Evaluation of a Novel Foot-Tickling Mechanism That Can Evoke Laughter [Don Samitha Elvitigala, Roger Boldu, Suranga Nanayakkara, and Denys J. C. Matthies / Transactions on Computer-Human Interaction]
Watch a foot-tickling machine discover the most ticklish spot on feet [Matthew Sparkes / New Scientist]