On the other hand, if user has experience with the same or similar products, there will be less likelihood to seek a warning. A key to determining cause in any accident analysis is to examine, not only at the environment at the time of the accident, but also at the actors' previous experience in that environment. Once the user notices a warning, it must be perceived. By this, I mean that the words or graphics must be read - the sensory input is given meaning by drawing on memory. In order to read a warning, it must be high contrast and, in the case of text, be large enough and rendered in a legible type font and family.
Exact size is partly a function of the user.
It's ironic that warnings on prescription bottles are often small even though the elderly, who have reduced vision, use prescription drugs with high frequency. Moreover, people often perceive the wrong part of the warning. There are many cases, for example, of a nurse looking at a vial and then injecting the patient with the wrong drug. In most cases, the nurse noticed the label but failed to perceive it. People have a tendency to generalize the cues that they use to make decisions.