"I'm not saying the 3DS doesn't have a pressure sensitive screen, but just because the piano plays louder when you tap harder doesn't necessarily prove it. The iPad, which has been proven not to have a pressure sensitive screen, still can sense whether you play piano keys in GarageBand harder or softer; see
http://www.apple.com/ipad/from-the-app-store/garageband.html (look towards the beginning of the video). I'm pretty sure it can be roughly calculated using some algorithm, as they did in GarageBand and could have done in Nintendogs. "
no.
3DS, DSlite DSi and DS all have RESISTIVE touch screens.
more pressure equals more resistance, which is measurable. Every DS has these screens. The 3DS screens are also higher resolution meaning that you can measure the resistance more accurately as the resistive layer is resolution dependant.
Resistive screens are the ONLY way to have a pressure sensitivety. (unless the pen registers pressure like a drawing tablet)
Capacitive screens (like smartphones, ipad, NGP) measure the surface area of finger/thumb in contact with the screen. If finger/thumb is pressed hard onto screen, a larger area of skin makes contact and this is guessed as a hard press. Capacitive screens cannot measure accurately pressure of any kind. They know if they have been touched, and the rest is guess work down to good programming.