"adult activity." Dellwo v. Pearson, 107 N.W.2d 859 (Minn 1961) Nicholsen v. Brown, 232 Or. 426, 374 P.2d 896 (1962) (automobile); Daniels v. Evans, 102 N.H. 407, 224 A. 2d 63 (1966) (motor scooter); Neumann. v. Shlansky, 58 Misc. 2d 128, 294 N.Y.S.2d 628 (1968 (playing golf)) What constitutes an "adult standard" may depend on local statute, and some have arbitrary age distinctions. Another exception is if the child is engaged in an "inherently dangerous activity." It is up to the trier of fact to decide if the activity is inherently dangerous. If they find that it is, the child must be held to an adult standard of care. Robinson v. Lindsay, 92 Wash.2d 410, 598 P.2d 2392 (1979) (snowmobile); Persons with disabilities A person with a disability is held to the same standard of care that an ordinary reasonable person would observe if they had that same disability. (Roberts v. State of Louisiana, 396 So.2d 566 (1981) (blind postal employee)) However, courts do not recognize a person with a mental disability to be subject to any such special standard, and are held to the "reasonable prudent person" standard, except when the onset of mental illness is unforeseeable and sudden (e.g., Breunig v. American Family Insurance Co., 45 Wis.2d 536, 173 N.W.2d 619 (1970) (sudden hallucinations while driving).) In some situations, this could work an injustice. Physical disabilities and conditions, such as blindness, deafness, short stature, or a club foot, or the weaknesses of age or sex, are treated merely as part of the "circumstances" under which a reasonable man must act. Duty to inform self of responsibilities A person engaged in a special and potentially dangerous activity must know or inquire of possible hazards or of any special duties and responsibilities inherent in that activity that might affect their ability to exercise reasonable prudent caution (cf, Delair v. McAdoo, 324 Pa. 392, 188 A. 181 (1936) (driving on worn tires).) Custom and practice of usage may be useful evidence for determining the usual standard, but not determinative of what a reasonable prudent person ought to be required to do or know (cf., Trimarco v. Klein, 58 N.Y. 2d 98 (1982) (showerdoor glass).) As Justice Holmes classic statement expresses it, "What usually is done may be evidence of what ought to be done, but what ought to be done is fixed by a standard of reasonable prudence, whether it is