This paper investigates the geometry of phi-features with a special emphasis on number and gender in Spanish. We address (i) whether number and gender evidence single- or multi-valued systems for their respective features, and (ii) whether number and gender are bundled together or split. 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 indicate that number but not gender in Spanish is multi-valued and offer novel support in favor of an agreement model in which number and gender are in separte projections and are valued independently. We also offer some considerations concerning parametric variation in such valuation.
