Acer a510 touch screen not responding to some fingers

Its more of a touch screen question than an Android question, but it pertains to an Android device so... I got my Dad an Acer A510 for Christmas and he has been very frustrated with it, especially the touch screen. I noticed that when he taps the screen it does not respond as readily as when I tap it. So my question is: do touch screens not respond as well to older (drier) fingers? He lives in New Mexico, and probably has relatively dry skin. Alternatively, is he just doing it wrong and skin type has nothing to do with it?