The present study tested Spanish heritage speakers' (HSs') production and selection of subjunctive mood in volitional clauses. Four groups participated to expose the effects of age on subjunctive acquisition: Spanish-dominant bilingual adults (SDBA; n = 18), HSs in fifth grade (HS5; n = 41), HSs in seventh/eighth grades (HS7/8; n = 34) and HS adults (HSA; n = 34). SDBAs produced and selected the subjunctive more than HS groups. There were no differences in production and selection between the HS7/8 and HSA groups, both of whom produced and selected subjunctive mood more frequently than the HS5 group. These results point toward protracted heritage language development. HSs selected the subjunctive more than they produced it, supporting theories that dissociate between mapping forms onto morphology and underlying syntactic competence. Finally, proficiency and frequency of use modulated individual variability between HSs. Results are addressed relative to incomplete acquisition, protracted development and feature reassembly.
