This paper investigates the geometry of phi-features, with a special emphasis on number and gender in Spanish. We address two sets of questions: (i) are number and gender bundled together or do they constitute separate categories, and (ii) does the internal feature composition of number and gender follow a single- or a multi-valued system? Given the lack of consensus on these issues based on primary data, we approach these questions experimentally, using the phenomenon of agreement attraction: a situation in which ungrammatical sequences are perceived as grammatical when one of the NPs is erroneously identified as determining agreement. Our results offer novel support in favor of an agreement model in which number and gender are in separte projections and are valued independently. In addition, our results indicate that number but not gender in Spanish is multi-valued.