Framing Effects and Modal Illusions: How to Characterize Framing Effects as An Intensional Phenomenon?

Empirically observed cognitive biases raise a challenge for the more formal and normative approach to rationality. Logicians, when facing these cases, can be led to reflect on some basic principles of theirs. Framing effects have been defined in terms of an intensional phenomenon (Schick, 1997). Framing effects can basically be defined as such: they occur when equivalent descriptions of a decision problem give rise to divergent decisions. Framing effects come in various guises: some possible risky choice, some goal, or some attribute of an object or a situation is framed and yields a framing effect. Different interpretations have been proposed for framing effects as well as a drastic recasting of decision-theory. My more specific intention here is to try to understand in which sense framing effects constitute an instance of intensionality, i.e. a violation of a principle of extensionality, or invariance, in decision-theory and to what extent this form of intensionality is related to other phenomena of non compliance with extensionality in logic and cognition. Arrow (1982) seems to be the first to characterize framing effects as displaying intensionality, as D. Kahnenam in his Nobel lecture reminds: “Framing effects violate a basic requirement of rationality which we called invariance (Kahneman and Tversky, 1984) and Arrow (1982) called extensionality”.