A}_1$ to add the attack relations $(b, c)$ and $(c, a)$. Given the attack relations $\{(a, b) (b, c), (c, a)\}$, many argumentation semantics resolve the arguments $\{a, b, c\}$ as $\{ \}$. Let us refer to the constructed argumentation framework as $AF'$. If ${\cal A}_1$ were to adopt the recommended attack relations, this implies that it now prefers $\{\}$ over all elements $\neq \{ \}$ in $2^{\{a, b, c\}}$, which in turn implies $\{\} \succeq \{ a \}$. This is inconsistent with the preference $\{ a \} \succeq \{ \}$ that ${\cal A}_1$ has given the set $\{a, b\}$ (see Figure \[fig:examples\]). In this case, ${\cal A}_1$ can be considered to behave *economically irrationally*. The phenomenon that the presence of additional choice options changes existing preferences–in this case $\{ a \} \succeq \{ \}$ to $\{ \} \succeq \{ a \}$ is called *reference dependence*. It is interesting to see that this change in preferences can be achieved without adding direct attack relations between arguments in $AF$; *i.e.* $AF'$ can be referred to as a *normal expansion* of $AF$. Hence, ${\cal A}_2$ can attempt to deceive ${\cal A}_1$ into changing its preferences without noticing. From the perspective of economic 