Heritage speakers’ grammars often differ from those of monolingually-raised speakers, yet certain types of language knowledge are especially likely to diverge (Polinsky, 2018; Sorace, 2011). One such area is the syntax-discourse interface, which includes syntactic structures that vary according to the discourse context. Because these constructions require integrating knowledge across linguistic domains, they are arguably more complex than parts of the linguistic system that do not require such integration, but scholars debate why this complexity causes divergence in heritage speakers’ grammars. Some argue heritage speakers’ grammatical knowledge is different (e.g., Silva-Corvalán, 1994). Others, though, suggest the problem is a constraint on processing, arguing that the difficulty of integrating different streams of information in real time overloads available processing resources (e.g., Sorace, 2011).

To contribute new evidence to this debate, we investigate information focus, a syntax/discourse interface construction in which new information is marked as prominent, in heritage Spanish. In Spanish, focus can be marked by non-canonical word order, as in (1), although there is variation (Olarrea, 2012).  

(1) [Context: Who bought a car?]
Compró un auto [el pintor]F.
bought a car the painter
‘The painter bought a car.’

We tested knowledge and processing of focus with 46 heritage speakers of Spanish (Chicago) and a control group of 41 monolingual native speakers of Spanish (Mexico). We measured participants’ focus-marking knowledge via a forced-choice task with a 2x2 design—context (subject/object focus) and word order (VOS/VSO). We also used a self-paced reading task (same 2x2 design) to measure participants’ real-time processing.

Results show heritage speakers’ judgments resemble monolinguals’: Both groups choose VOS to realize subject focus around 2/3 of the time (monolinguals 63.9%; heritage speakers 66.9%). Yet when it comes to processing, heritage speakers diverge substantially from the monolingual pattern. The length-adjusted reading times show monolinguals process contextually appropriate word orders faster than inappropriate orders, while heritage speakers display no context-dependent pattern. These results suggest divergence at the syntax/discourse interface may indeed be due to constraints on processing complex linguistic information, as proposed by Sorace (2011).