Viewed from an anthropological perspective, hacking is a cultural tradition affirming group solidarity, but some hacks can also be viewed as individualistic creative or artistic expression. For example, the "Massachusetts Toolpike" hack was a clear instance of installation art or environmental art. Hacks which involve staged public actions (e.g. a zombie march or the Time Traveler Convention of 2005) are clearly a form of performance art, often combined with body art and cosplay. Still other hacks have a strong conceptual art flavor, often satirizing other purported works of conceptual art. Sometimes the boundaries have been deliberately blurred, for example when a satirical work of "conceptual art" ("No Knife: a study in mixed media earth tones, number three") was surreptitiously added to a "serious" art gallery show at the List Visual Arts Center.