Evaluation of Verbal Behavior in Older Adults

Adults 65 years and older make up approximately 13% of the U.S. population. Projections indicate that this age group will reach over 16% in 2020 and over 20% in 2050 (Vincent & Velkoff, 2010). In 2000, 10.8% of older adults reported that they had a mental disability, defined as difficulty with learning, remembering, or concentrating (Waldrop & Stern, 2003). Approximately 5% of adults over 65 years of age have some form of dementia (Kempler, 2005). Dementia is a condition characterized by memory loss and at least one other area of cognitive dysfunction, including aphasia, apraxia, agnosia, or disturbed executive functioning (American Psychiatric Association, 2000). Estimates indicate that the number of adults with dementia diagnoses worldwide will grow from 25 million in 2000 to 63 million in 2030 (Kempler, 2005). With increasing numbers of older adults diagnosed with dementia, developing appropriate assessment and treatment methods is of critical importance. Aphasia, one of the cognitive dysfunctions included in the dementia diagnosis, is described as “deterioration of language function” (American Psychiatric Association, 2000, p. 148). Although changes in language abilities are not unique to those diagnosed with dementia (Benson & Ardila, 1996; Kempler, 2005), research suggests that individuals with dementia diagnoses perform worse on verbal tasks than similar-aged peers without dementia diagnoses (Benson & Ardila, 1996). Early and adequate assessment of language deterioration of older adults is important, because determining the degree of language deterioration relative to peers helps with the diagnosis of dementia and may allow early intervention for language deficits associated with dementia. Traditional assessments of language focus on response topographies without addressing the function of the responses. Although topographical information may be useful for characterizing language deficits, it does not explain the cause of the deficits. Topographical information alone is insufficient for designing most effective interventions (Esch, LaLonde, & Esch, 2010). Therefore, developing assessment methods that identify the function of verbal responses may be necessary for improving interventions for older adults with deteriorating language skills. Skinner (1957) offered a conceptual approach to the analysis of language that viewed language as operant behavior, behavior that is influenced by a range of contextual features and maintained by its consequences. He proposed a classification system of verbal operants, each controlled by a unique set of antecedents and consequences. The primary verbal operants identified by Skinner and addressed in the present study include echoics, tacts, intraverbals, and mands. Skinner (1957) proposed that each verbal operant is functionally independent of the others, meaning that a specific response may be acquired under one set of controlling conditions, but topographically identical responses may not occur under other controlling conditions. He also proposed a functional approach to language deterioration stating, “What has been damaged in aphasia is clearly the functional control of behavior, and the damage respects the line of control” (p. 195). This suggests that a response that was previously in an individual's repertoire might continue to occur under certain controlling conditions, but that same response might no longer occur under other conditions. For example, a person who had used the word “spoon” correctly across contexts in the past may be able to currently name a photo of a spoon, yet have difficulty finishing the phrase, “you eat with a knife, fork and _______.” Skinner suggested that individuals can have deficits specific to speaking or listening, and he added specificity by predicting that speaker behavior might degrade in a manner that is compatible with the distinction between verbal operants. Specifically, “The order of damage seems to follow the order of ‘difficulty’ deducible from the availability of a minimal repertoire. Textual and echoic behavior often survive . . . while intraverbals and tacts appear to be most vulnerable” (Skinner, 1957, p. 219). Additionally, Skinner noted that “Damage is usually most severe in verbal behavior receiving generalized reinforcement” (p. 219). Mands are not reinforced with generalized reinforcers; instead, the controlling conditions for mands involve motivating operations and characteristic consequences (Michael, 1988). Therefore, it is possible that mands are more resilient against decline than other verbal operants, such as tacts or intraverbals. Researchers have attempted to evaluate the functional independence of verbal operants as it relates to acquisition and deterioration of verbal behavior. Many studies report data consistent with functional independence during verbal skill acquisition, whereas other studies reveal transfer of training across verbal operants (for a review, see Sautter & LeBlanc, 2006). Notably, there are procedural variations across studies evaluating functional independence, which might account for these differences in findings. With regard to deterioration, a rehabilitation study for adults who had sustained a traumatic brain injury (TBI) (Sundberg, San Juan, Dawdy, & Arguelles, 1990) revealed that verbal operants were differentially affected post-injury; that is, echoics and textuals were strong but tacts, mands, and intraverbals were weak. Furthermore, these adults acquired verbal operants after their injury in a different manner than children with developmental disabilities, who were presumably acquiring the skills for the first time. Prior research had shown that direct mand training may be necessary for children with developmental disabilities to learn mands, and these children learned mands quicker than tacts. However, adults who had a sustained a TBI acquired tacts and intraverbals quicker than mands, and direct mand training was less effective for teaching mands than transfer of training from tacts or intraverbals. These findings may suggest that unique assessment and intervention strategies are needed for sophisticated versus naive speakers, as well as for speakers who are losing, as opposed to acquiring, verbal skills. To the authors' knowledge, researchers have not yet developed and evaluated language assessment tools for age-related language deficits based on Skinner's functional verbal behavior model. Baker, LeBlanc, and Raetz (2008) provided a taxonomy of aphasia and recommendations for how to assess verbal behavior in older adults based on a functional approach; however, empirical data were not provided. Other researchers have evaluated verbal behavior interventions with older adults with some success (e.g., Dixon, Baker, & Sadowski, 2011), but the interventions were not derived from a functional assessment. The Verbal Behavior Milestones Assessment and Placement Program (VB-MAPP; Sundberg, 2008) is a language assessment measure that is based on Skinner's model of verbal behavior. It is used to assess language delays in young children, and the results of the assessment lead to specific intervention plans. A similar assessment model is needed for older adults who might be losing language skills. If such an assessment reveals functionally independent verbal operant deficits in older adults, then the next phase of research can be undertaken; the creation and evaluation of function-based interventions. The current research is a first step in this process; the development and preliminary evaluation of a function-based assessment for language deficits in older adults with and without dementia. There were two primary research questions. First, in what ways do verbal behavior strengths and deficits differ between older adults with and without dementia? Second, does language deteriorate differentially across the verbal operants?