Thesis advisor: Sara Cordes / The format of our quantity representations is a contentious topic of study in the field of numerical cognition with researchers debating whether we use discrete (i.e. number) or continuous (e.g. area, time, volume or density) cues to make quantity judgements. It has been proposed (through the Sense of Magnitude Theory) that continuous quantities are more perceptual in nature and thus do not require the higher order cognitive processes needed to represent abstract number, making it unlikely that number is tracked in the presence of perceptual quantities. In the current dissertation, I examined claims made by the Sense of Magnitude theory by 1) investigating the accuracy with which we represent continuous quantities and the mental processes we may engage in when representing these quantities and by, 2) comparing the relative salience of discrete and continuous quantities and how this may change across development. In Project 1, I investigated the accuracy with which infants make element size discriminations and whether this ability becomes more precise with age. Project 2 examined the precision with which adults track cumulative area and uncover the process by which they do so. Lastly, Project 3 explored the relative salience of number for preschoolers by assessing their “Spontaneous Focusing on Number.” Together, findings from these three projects undermine claims stating that humans at all stages of development are better at, and prefer to, attend to continuous quantities over discrete number. Instead I propose that this dissertation suggests that humans at all stages of development are strongly attuned to number in their environment. This work not only provides insight into the way we represent quantity in our day to day lives, but it can help us understand where individual difference in mathematical achievement in school may stem from. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Psychology.