Touch between people is an integral part of human life. Touch is used to convey information, emotions, and other social cues. Still, everyday remote communication remains mainly auditive or audio-visual. The theme of this article, interpersonal haptic communication, refers to any communication system that supports mediation of touch between two or more persons. We first present a scoping review of the state of the art in interpersonal haptic communication, including physiological and psychological basis of touch, affective and social touch, and mediated social touch. We then discuss emerging research themes that shape the future of interpersonal haptic communication, identify research gaps and propose key research directions for each theme. Finally, societal impact and ethical aspects are discussed.

Semiautonomous driving still requires the driver's control and attention in certain situations. Especially control transitions, i.e. take-over and hand-over situations, are important for safety. Our aim was to study control transitions supported by unimodal (i.e. visual, auditory, or haptic) or multimodal (i.e. visual, auditory and haptic) signals indicating change from manual to autonomous driving and vice versa. The signals were abstract visual blinks, auditory beeps, or haptic vibrations. The task was to take over driving while either looking through the windshield or playing a game. In addition, in half of the control transitions a feedback signal indicated successful control transition. The results showed that a secondary task slowed down the reaction times, but there was a great variation between individuals. In general, the response to auditory signal was slower than to visual, haptic, or multimodal signals. Moreover, users preferred feedback during control transitions but this slowed down the reaction time.

The aim was to study if odors evaporated by an olfactory display prototype can be used to affect participants' cognitive and emotionrelated responses to audio-visual stimuli, and whether the display can benefit from objective measurement of the odors. The results showed that odors and videos had significant effects on participants' responses. For instance, odors increased pleasantness ratings especially when the odor was authentic and the video was congurent with odors. The objective measurement of the odors was shown to be useful. The measurement data was classified with 100% accuracy removing the need to speculate whether the odor presentation apparatus is working properly.

The present aim was to study the preference of tactile feedback stimulations given by non-physical (i.e., solid) piezo-actuated buttons. Participants (n=16) ranked 16 different tactile feedback stimuli varied by 4 output delays and 4 vibration durations. The results showed that the mean ranks of the stimuli differed significantly from each other. The timing parameters of delay and duration interacted with each other, for example, so that preference of certain vibration duration fluctuated in response to different output delays. Using a very short time window (i.e., 10-453 ms) combining both delay and duration parameters of the feedback could result either in favorable or significantly less favorable subjective experience. The results suggest that a preferred perception of tactile feedback from non-physical buttons requires careful design and controlling of the timing parameters.

The present aim was to study if thermal stimuli presented to the palm can affect emotional responses when measured with emotion related subjective rating scales and changes in skin conductance response (SCR). Two target temperatures, cold and warm, were created by either decreasing or increasing the temperature of the stimulus 4 °C in respect to the participants current hand temperature. Both cold and warm stimuli were presented by using two presentation methods, i.e., dynamic and pre-adjusted. The results showed that both the dynamic and pre-adjusted warm stimuli elevated the ratings of arousal and dominance. In addition, the pre-adjusted warm and cold stimuli elevated the SCR. The results suggest that especially pre-adjusted warm stimuli can be seen as effective in activating the autonomic nervous system and arousal and dominance dimensions of the affective rating space.

A prototype of friction-based horizontally rotating fingertip stimulator was used to investigate emotional experiences and behavioral responses to haptic stimulation. The rotation style of 12 different stimuli was varied by burst length (i.e., 20, 50, 100 ms), continuity (i.e., continuous and discontinuous), and direction (e.g., forward and backward). Using these stimuli 528 stimulus pairs were presented to 12 subjects who were to distinguish if stimuli in each pair were the same or different. Then they rated the stimuli using four scales measuring the pleasantness, arousal, approachability, and dominance qualities of the 12 stimuli. The results showed that continuous forward-backward rotating stimuli were rated as significantly more unpleasant, arousing, avoidable, and dominating than other types of stimulations (e.g., discontinuous forward rotation). The reaction times to these stimuli were significantly faster than reaction times to discontinuous forward and backward rotating stimuli. The results clearly suggest that even simple haptic stimulation can carry emotional information. The results can be utilized when making use of haptics in human-technology interaction.

Haptic stimulation in motion has been studied only little earlier. To provide guidance for designing haptic interfaces for mobile use we carried out an initial experiment using C-2 actuators. 16 participants attended in the experiment to find out whether there is a difference in perceiving low-amplitude vibrotactile stimuli when exposed to minimal and moderate physical exertion. A stationary bike was used to control the exertion. Four body locations (wrist, leg, chest and back), two stimulus durations (1000 ms and 2000 ms) and two motion conditions with the stationary bicycle (still and moderate pedaling) were applied. It was found that cycling had significant effect on both the perception accuracy and the reaction times with selected stimuli. Stimulus amplitudes used in this experiment can be used to help haptic design for mobile users.