We compared the processing of natural language quantifiers in a group of patients with schizophrenia and a healthy control group. In both groups, the difficulty of the quantifiers was consistent with computational predictions, and patients with schizophrenia took more time to solve the problems. However, they were significantly less accurate only with proportional quantifiers, like more than half. This can be explained by noting that, according to the complexity perspective, only proportional quantifiers require working memory engagement. Learning outcomes: (1) Working memory deficits can be a source of language disorders in schizophrenia. (2) Processing of proportional quantifiers, like "more than half" or "less than half" involves working memory. (3) Patients with schizophrenia are less accurate only with proportional quantifiers, like "more than half". (4) This result support the computational model of quantifiers processing. (Contains 3 tables and 3 figures.)