Sensitivity of an input device means how much interaction needs to be performed to achieve the wanted result. It can be measured in:
- Distance - how far an analog input device needs to be moved to affect the active element on the screen (e.g., mouse or joystick);
- Time - how long an input device needs to transmit a signal to be considered an interaction (e.g., keyboard or touchscreens);
- Force - how much pressure needs to be applied to be considered an interaction (e.g., Wacom tablets).
In addition, the term "touchscreen" refers to several sensing technologies that require various amounts of force and time to trigger a signal. However, most of them are incapable of measuring the force applied. The three most common ones are:
- Capacitive touch has become the most common group of technologies (there're several similar methods of varying accuracy - even within the same type). These technologies power the overwhelming majority of today's touchscreens. The downsides include the inability to calculate the pressure force & the recognition of the slightest touches because of the inherent properties of capacitance.
- Resistive screens transmit the signal from the point where the 2 conductive layers make contact (pressure is applied on the outer shell). The force required to make contact varies depending on the device but is generally more than what capacitive screens need. Resistive screens can supposedly calculate the pressure force but I haven't seen any applications or mass-market products taking advantage of it.
- Infrared is the cheapest way to touch-enable a large screen. In reality, this is a pseudo-touchscreen technology since no real touching of the screen's surface is necessary: an object just needs to obstruct the IR rays at a particular level close to the screen. As a result, it's incapable of reading the pressure force and is far less accurate than capacitive and resistive technologies.
There's also electromagnetic resonance, which isn't considered a touchscreen technology because it requires the special stylus to recognize interactions with the surface. It was used in the original Tablet PCs in early to mid-00's and is currently used in Wacom Cintiq monitors (Wacom holds the patent to it).
EMR is the most advanced technology but it's the most expensive one despite being in the market for over 20 years so it's not widespread. It currently supports up to 2048 pressure levels for the stylus pen. The native drivers do allow some modification of pressure sensitivity and applications built to take advantage of the technology, such as Adobe Photoshop, have the option of completely disabling pressure sensitivity.
Now, that we know the measurements of sensitivity and the capabilities of the modern technologies let's see how touch sensitivity can be adjusted.
It's safe to assume that you were referring to capacitive screens since they are the most commonly used in consumer devices nowadays. Since the technology requires very little force to produce a signal, sensitivity should control the time the force is applied to the screen. The problem with this approach is that a tap or a mouse click lasts generally up to 100ms, which is very short time and is likely to match the duration of an accidental contact. As a result, increasing such measure of sensitivity will require users to touch the screen for unnaturally long periods of time. Therefore, the experience flaw is in the technology's inherent properties and not in the accompanying software.
Technology is also to blame for the poor responsiveness in some resistive and infrared screens because both of them require significant physical force to trigger a signal.