How to measure emotion with tap pressure
I wanted to validate my theory: Tap pressure is connected to the emotional state of the tapper. This means that I need to know how people feel, and then measure the pressure they exert on the screen when tapping. I ended up using photos from the Geneva Affective Picture Database. These photos have been thoroughly researched for the emotional reaction they elicit from people when they see them. So now we have a way of knowing how people feel. On the other hand, we need to measure tap pressure. The measuring of tap pressure was done with the 3D touch screen that Apple incorporates in the iPhone 6s and newer. To get people to tap the screen when they saw a picture, I would let them solve a tiny puzzle after five seconds of looking at the picture. The puzzle was very simple and always required four taps. So in short: People see a picture, after five seconds they tap the screen four times, and I measure the tap pressures of those taps for that particular photo. Easy right?
51 test participants later..
… and I got all the data I needed to start analyzing the results! To get to the essence of data, I used an application called SPSS, which allows me to run complicated statistical analysis on the data. I ran a multiple linear regression test for those who want to know, but more importantly, it turned out that there is no relationship
between tap pressure and emotion. What is interesting about that is that literature definitely
seems to expect a relationship between the two. So why does my research contradict the expectations set by literature and intuition? One explanation is that the tap pressure was measured on a scale from 0.0 to 6.67, but al measurements were between 0.2 and 0.5. The full scale of possible measurements was never used! This can mean two things: Either the differences in tap pressure are more subtle and require a more sensitive sensor, or there just is no relationship between tap pressure and emotion. Another explanation may be that every person is different in how they are holding a phone, how big their hands are, and where they tap on the screen. These differences, combined with a small bandwidth of measurements, might be the source of the contradicting result. Hopefully a fellow researcher finds a non-invasive way of measuring emotion, either by repeating my experiment with the issues fixed, or by using an entirely different approach.
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