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Maintaining Treatment Gains
Persons who work with individuals with developmental delays are likely to confront the question of whether the gains the individuals make in their programs generated through the classroom or clinic will be maintained after the individuals leave those settings. An intervention is of only limited value if it fails to maintain its effects over time. A study published by Lovaas, Koegel, Simmons, and Long in 1973 illustrates this problem (see Chapter 3 for a more detailed review). In this study, a group of children were treated with intensive behavioural intervention over a period of about 14 months. During this time, the children made substantial progress in speech, toy play, and social interactions while self-stimulatory and tantrumous behaviours decreased. At the end of treatment, about half of the children entered a state institution where they received a great deal of non-contingent care and love and access to special education classes. Several of the remaining children in this study were not discharged to the state institution but rather were returned to their parents who had been trained in the implementation of behavioural treatment. When the institutionalized children were assessed 2 years later, they had all regressed. It was possible, however, to reestablish many of their original gains by introducing the treatment a second time. Unfortunately, these gains were again lost at the time of the second follow-up. The children who had returned home to their parents, however, had not regressed at follow-up. Such results demonstrate that having parents, significant adults, and peers rather than only aides involved in the several facets of treatment is essential for maintaining treatment gains.
A second follow-up study by McEachin, Smith, and Lovaas was published in 1993 and incorporated many of the recommendations we present in this chapter. In brief, the follow-up data generated from the 1993 study are much more encouraging than the results of the earlier study: The 1993 follow-up study showed that 9 of the 19 children who had received the revised intervention maintained the treatment gains 3 to 12 years after the termination of treatment. Ten of the remaining children were placed in special
education classes after treatment, many of them regressing over time. The reason the best-outcome group did so well is likely to be based at least partially on the fact that the children composing this group continued to receive treatment in the sense that they were integrated with and learned from typical children.
Whether or not a person maintains the gains made during an intervention is probably a function of a number of variables. Whether a person remembers, recalls, or otherwise maintains what has been learned in the past is a function of changes in that person's environment as well as changes in that person's central nervous system (in the case of individuals with developmental delays, such change is instigated by organic damage). This chapter concerns only the environmental changes contributing to the maintenance of treatment gains.
The means by which the nervous systems of individuals with developmental delays process stimuli resulting in excellent versus poor recall are unknown. What is known, however, is that individuals with autism display superior memory of responses to simple stimuli, such as recalling digits or other visual presentations, when compared to other individuals with delays or typical individuals of the same mental age as the individuals with autism. However, individuals with autism exhibit inferior memory skills when presented with tasks in which the stimulus and response involve different sensory modalities (e.g., auditory and visual). For example, on a task that requires an individual to hear a verbal stimulus and make a visual-motor response (e.g., 'Touch nose'), individuals with autism fail to retain the correct response more often than other individuals of the same mental age. Whether this phenomenon is due to the individuals' limited exposure to early educational materials or unique characteristics of the individuals' nervous systems is not known. In any case, it seems reasonable to take advantage of what is known about improving memory and then build upon and incorporate such knowledge into one's intervention program. In this chapter, we consider three basic procedures to enhance the retention of learned material. The first centres on reinforcement control, the second focuses on stimulus control, and the third deals with consistent findings from memory research concerning programming and spacing of trials.
There are two ways in which reinforcers may be manipulated so as to enhance the likelihood that learned behaviour will be retained. These are discussed in this section.
► 1. Manipulating reinforcement schedules. Schedules of reinforcement vary in type. One way to deliver reinforcement is to give it contingent on every correct response. This schedule of reinforcement is known as a continuous schedule. A second procedure is to provide reinforcement on a more intermittent basis, such as once every eighth correct response or once every 10 minutes. These are called ratio schedules of reinforcement and interval schedules of reinforcement, respectively, depending on whether a certain number of responses or a certain amount of time elapsed since the last response is used to determine when the reinforcement is delivered.
One can differentiate between high-density and low-density schedules of reinforcement by analyzing the frequency with which reinforcement is provided. One can also differentiate between fixed schedules and variable schedules by observing whether reinforcement is always given after a fixed number of behaviours or amount of time (e.g., reinforcement is always given after every three correct responses or after every 5 minutes) or an irregular number of behaviours or interval of time (e.g., reinforcement is given after a random number of behaviours or random amount of time). For example, in a variable ratio schedule with a density of five, the average number of responses between reinforcements is five, but the number of responses between any two reinforcements may be more or less than five.
It is generally known that continuous reinforcement (i.e., reinforcement for each correct response) is the preferred schedule to use as a behaviour is being acquired given that fixed, high-density schedules result in relatively rapid acquisition. However, once the behaviour is established, shifting to a thinner variable schedule yields more resistance to extinction; thus, the behaviour will be maintained for longer periods of time through this type of schedule. Such a procedure is similar to methods parents often use to raise a typical child. That is, one often provides a dense schedule of reinforcement for a child when the child is very young and is just learning particular skills. As the child grows older, however, one expects that the child will behave appropriately without having to be reinforced so often.
► 2. Selection of reinforcers. Reinforcers that are likely to be present in the student's natural, everyday settings should be used. Note that food reinforcers are not likely to be present with sufficient frequency to maintain learned behaviours once the student enters a new environment. Thus, the student will learn to discriminate between those environments in which she receives food reinforcement and those in which she does not. Consequently, the student's appropriate behaviours will rapidly extinguish in new environments. To avoid such a loss, one must gradually transfer from the use of food reinforcement to reinforcers available in the student's everyday environment. More natural reinforcers are likely to be secondary or acquired reinforcers (reinforcers that are learned, such as praise and recognition) as opposed to primary reinforcers.
If a student learns a certain behaviour in a particular setting and in the presence of a limited number of persons, such as parents and an aide, it is unlikely that this behaviour will maintain itself once the environment is changed. In technical literature, this phenomenon is said to result from narrow stimulus control. To avoid such an occurrence, one must arrange for broad stimulus control over the student's behaviours such that various adults and diverse environments come to cue consistent responding. An example from the everyday lives of typical children may illustrate this problem well. While in the presence of family, one may see a child engage in certain kinds of appropriate and pleasing behaviours. One often hopes that these behaviours learned at home will be transferred to the child's school or peer group. Parents often become quite concerned when they observe their child behave in a radically different manner when he is outside the family; the stimulus control the parents exercise in the home may be nonexistent once the child leaves the home.
There are two strategies for creating common stimuli across settings to help maintain consistency in the student's behaviours. First, one must make certain that the discriminative stimuli present in the teaching environment are also present in the student's everyday environment. For example, students with developmental delays are more likely to generalize the skills they learn in the Receptive Labelling of Objects Program (in Chapter 17) if the labels taught are acquired through the use of three-dimensional objects rather than pictures of objects. Students with developmental delays are also more likely to generalize treatment gains if the persons or situations they encounter outside the instructional setting are similar to those from within the treatment environment.
The second strategy involves teaching the student to respond to numerous exemplars of stimuli. For example, broader stimulus control (greater generalization) will be gained if the student is taught to label not only one dog but several dogs of different sizes, shapes, and colours. In technical literature, such a strategy is referred to as the method of sufficient examples, given that it involves teaching enough examples of certain stimuli that the student learns to generalize from these examples to novel examples.
There is a third issue to contend with when strategiz-ing the establishment of stimulus control: When a student enters a new environment, that environment may contain stimuli that distract the student from exhibiting previously learned behaviours or, conceivably, the student may be taught competing behaviours through exposure to certain settings. To compensate for such occurrences, the student should be taught in environments as similar to his everyday settings as possible. In addition, if gains are made in one setting, then an effort should be made to transfer those gains to other settings and other persons. For example, if a student is treated by one professional (e.g., either a speech therapist or a teacher) or if treatment occurs in a single setting (e.g., a single office or classroom), it is likely that whatever gains the student demonstrates with the original person or in the original setting will not be cued by novel persons or settings.
A great deal of research concerning memory facilitation in typical individuals has been carried out and applied to help individuals better remember information they need in order to function in new and different environments. Many of these techniques for improving memory are very involved and too complicated for use in the treatment of students with developmental delays. However, a technique labelled spacing or expanded trials has proven to be very helpful and particularly appropriate for facilitating recall in students with developmental delays.
Spacing is a technique that consists of gradually increasing the time interval separating trials of a new response after that response is acquired through mass tri-aling. The exact reason why spacing facilitates memory is largely unknown, but it may be because such a procedure requires the student to practice remembering. The more difficult the practice is (i.e., the longer the time interval between trials), the more the student is prepared to remember the correct response after formal teaching is over.
Once a particular behaviour is acquired in mass trials, a spacing procedure may be started by expanding the time interval between trials, beginning with short intervals and gradually increasing to longer ones. This may seem contradictory to what was advised in earlier portions of this manual where we recommended that the teacher minimize inter-trial intervals. It is important that the teacher discriminate, however, between the acquisition of behaviour and the retention of learned material. In regard to designing treatment, spacing trials relates closely to what we refer to as rehearsing or practicing mastered material placed on a maintenance schedule. That is, when a task is first acquired, it should be rehearsed after relatively short intervals (e.g., 1 hour).
As the behaviour becomes more established, however, the times at which it is practiced can be spaced over one day, then every third day, then every week, and so on. Note that the speed with which the intervals are increased must be determined by the performance of the student. For example, if at a particular interval the student's performance deteriorates, it is necessary to re-establish the target behaviour by shortening the inter-trial interval before again expanding the amount of time between trials.
As a common example of the importance of spacing in facilitating recall, we can draw upon several studies (Charlop, Kurtz, & Milstein, 1992; Davis, Smith, &. Donahoe, 2002; Dunlap, 1984) that have generated a similar result: In teaching a course, one can either teach the entire course in one day or spread instruction over several days, perhaps even months. If the course is taught in one day, retention of the material is likely to be minimal. In contrast, if the course material is divided up and taught incrementally, one's retention of it will likely exceed that gained in the rapid course.
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