Free association is a founding concept in psychoanalysis that refers to the way the patient will more or less freely pass from one representation to another, thus forming a therapeutic method to address psychic reality. This article examines the role of associativity in psychoanalysis and neurosciences in order to improve dialogues between clinical and cognitive models. We first propose a global overview of the historical origins of the concept of associativity in psychoanalysis and examine, in particular, how Freud established the principles of free association. From Freud's distinction between primary and secondary processes, we then proceed to compare the psychoanalytic approach to research about associativity originating from the cognitive neurosciences and neuropsychoanalysis. Finally, we address the impacts of this contemporary research on clinical practice and articulate the notion of symbolizing transmodality to define the passage from one form of associativity to another within the therapeutic process