Exploring the abstractness of number retrieval cues in the computation of subject-verb agreement in comprehension

•Memory interference can cause agreement checking with non-subjects (‘attraction’).•Conjoined singular NPs are syntactically plural but lack an unequivocal morphological exponent.•Attraction with conjoined singular NPs indicates retrieval models must include abstract cues.•Singular NPs with conjoined adjectives also elicited some agreement attraction.