Many individuals with intellectual and developmental disabilities have communication deficits (Smith et al., 2020), and research suggests that various communication modalities, including vocalizations, picture exchange, sign, and assistive technologies, can be taught (McLean et al., 1996). However, because communication modalities are often selected arbitrarily (Orozco et al., 2023), the acquisition and maintenance of communication may be affected (Kunnavatana et al., 2018). Furthermore, little research has focused on the acquisition of communication modalities in adults with intellectual and developmental disabilities. In Study 1, we replicated a prerequisite assessment (Valentino et al., 2019) with a large number of adults with intellectual and developmental disabilities who were referred for communication deficits. In Study 2, we replicated and extended Valentino et al. (2019) and Gutierrez et al. (2007) by conducting a preliminary evaluation of the validity of the prerequisite assessment with a subset of participants from Study 1. That is, we conducted a mand evaluation to evaluate the degree to which discriminated manding occurred across common modalities. Results of Study 1 showed that many participants displayed weak potential prerequisite skills for most, if not all, communication modalities. The results of Study 2 showed that participants’ potential prerequisite skills from Study 1 sometimes mapped onto modalities acquired during the mand evaluation, but additional manipulations were sometimes necessary for differentiated responding to be acquired with these modalities. For some participants, another modality was necessary (i.e., item exchange).
