  Though the ability of human beings to deal with probabilities has been put
into question, the assessment of rarity is a crucial competence underlying much
of human decision-making and is pervasive in spontaneous narrative behaviour.
This paper proposes a new model of rarity and randomness assessment, designed
to be cognitively plausible. Intuitive randomness is defined as a function of
structural complexity. It is thus possible to assign probability to events
without being obliged to consider the set of alternatives. The model is tested
on Lottery sequences and compared with subjects' preferences.
