Scanning the Invisible: Framing Diagrammatic Cognition in Experimental Particle Physics Javier Anta Universitat de Barcelona, Spain Abstract. In this study, I aim to develop a cognitivist evaluation of how seman- tically-driven and rule-based diagrammatic reasoning (Barwise & Etchemendy, 1996) were psychologically possible for particular cases of scientific practice: an actual trackless path reconstruction in bubble chamber experiments. I will follow an exhaustive analysis of the diagrammatic operations (fleshing out eve- ry single diagrammatic operation actually performed by human “scanners”) and a cognitivist study on which are the psychological mechanisms underlying these scientific activities. I will propose “cognitive imagery projection and manipula- tion” (CIPM) as the most plausible psychological (perceptu- al/attentional/cognitive) mechanism matching the specific explanatory require- ments for the case study, outlining the most significant current theories about this mental phenomenon (Briscoe, 2008; Nanay, 2011) and how they rely on some recent experimental evidence (Shimojima; 2011). I will conclude by claiming that diagrammatic scientific cognition might be the theoretical key to understand how scientific knowledge had been non-linguistically produced all along history. Keywords: Diagrammatic Reasoning, Imagery, Particle Physics 1 Introduction and methodology In this paper, I aim to develop a cognitivist evaluation of how semantically-driven and rule-based diagrammatic reasoning (departing from the works of Barwise & Etche- mendy, [1] and Shimojima, [11]) could be psychologically possible, for particular cases of scientific practice: an actual trackless path reconstruction in bubble chamber experiments. I will follow an exhaustive analysis of the diagrammatic operations and a cognitivist study on which are the psychological mechanisms underlying these dia- grammatic operations. The case study and their particular scientific-experimental procedures were inserted within the context of experimental particle physics settled in Berkeley ([4]), as it will be briefly described in the next section. Following these methodological preliminaries, I will flesh out (in Section 3) every single diagrammat- ic operation actually performed by “scanners” in a trackless path reconstruc- tion/abduction of an invisible particle within a bubble chamber picture. Afterwards in Sections 4 and 5, I will propose “cognitive imagery projection and manipulation” (CIPM) as the most plausible integrative psychological (perceptu-