01 Jun At least two paragraphs summarizing the entirety of the readings.? For example, what is the main idea of the readings, when there are multiple chapters or articles, what ties them together?
- At least two paragraphs summarizing the entirety of the readings. For example, what is the main idea of the readings, when there are multiple chapters or articles, what ties them together? When citing, use APA style (author/s, (date), page). Some weeks this section will be shorter and other weeks it will be longer based on the week’s readings.
- At least one paragraph discussing two concepts that you found particularly interesting, or that challenged your belief system. Reference the specific readings and cite your source using APA style (author/s ( date), page)
- At least one paragraph discussing the impact of your reading to your practice. For example, what should a behavior analyst DO to be most reflective of this content? Reference the specific readings and cite your source using APA style (author/s, (date), page).
The Behavior Analyst 2009, 32, 205–240 No. 1 (Spring)
A Case Study in the Misrepresentation of Applied Behavior Analysis in Autism: The Gernsbacher Lectures
Edward K. Morris University of Kansas
I know that most men, including those at ease with problems of the greatest complexity, can seldom accept the simplest and most obvious truth if it be such as would oblige them to admit the falsity of conclusions which they have proudly taught to others, and which they have woven, thread by thread, into the fabrics of their life. (Tolstoy, 1894)
This article presents a case study in the misrepresentation of applied behavior analysis for autism based on Morton Ann Gernsbacher’s presentation of a lecture titled ‘‘The Science of Autism: Beyond the Myths and Misconceptions.’’ Her misrepresentations involve the characterization of applied behavior analysis, descriptions of practice guidelines, reviews of the treatment literature, presentations of the clinical trials research, and conclusions about those trials (e.g., children’s improvements are due to development, not applied behavior analysis). The article also reviews applied behavior analysis’ professional endorsements and research support, and addresses issues in professional conduct. It ends by noting the deleterious effects that misrepresenting any research on autism (e.g., biological, developmental, behavioral) have on our understanding and treating it in a transdisciplinary context.
Key words: autism, applied behavior analysis, misrepresentation, research methodology, ethics
This manuscript is unconventional. I did not write it for publication, but for students at the University of Kansas (KU), colleagues and ac- quaintances on and off campus, families of children with autism,1
I thank many colleagues for indulging my many questions about autism and its treat- ment and for their constructive comments on the manuscript’s earlier drafts. I acknowledge them by including their fine work in my reference section.
Correspondence may be sent to the author at the Department of Applied Behavioral Science, 4020 Dole Center for Human Devel- opment, University of Kansas, 1000 Sunny- side Avenue, Lawrence, Kansas 66045 (e-mail: [email protected]).
1 According to the American Psychiatric Asso- ciation’s (2000) Diagnostic and Statistical Man- ual of Mental Disorders, autism is a neurode- velopmental disorder whose core features are impairments in communication (e.g., lack of spoken language) and social interactions (e.g., lack of social or emotional reciprocity) and restricted, repetitive, and stereotyped patterns of behavior, interests, or activities (e.g., rituals, self-stimulation) (p. 75). These features are often associated with other conditions that vary from severe to mild within and across individuals (e.g., mental retardation, chronic aberrant behavior). Autism also falls within
and ultimately for those children. I also wrote it for myself, both as a professional and as a person. Profes- sionally, I was obliged to respond to recent misrepresentations of applied behavior analysis in autism. Person- ally, I was aggravated enough that I thought that writing the manuscript might prove cathartic. In the end, though, the catharsis was more intel- lectual than emotional. I learned a great deal about autism research and treatment, and am now better able to address their misrepresentation. This sense of intellectual satisfaction, however, did not fully overcome my aggravation, but so be it.
INTRODUCTION
At the invitation of KU’s Depart- ment of Psychology, Morton Ann Gernsbacher (University of Wiscon- sin) gave its Fern Forman Lecture on September 27, 2007. It was titled
the broader diagnosis of the autism spectrum disorders, which include autism, Asperger syndrome, and pervasive developmental disor- der not otherwise specified.
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‘‘The Science of Autism: Beyond the Myths and Misconceptions.’’ Gerns- bacher is an award-winning educator, a well-funded and well-published researcher, and the 2006–2007 presi- dent of the Association for Psycho- logical Science (APS). Her research is on cognitive mechanisms hypothe- sized to underlie language compre- hension (e.g., Traxler & Gernsbacher, 2006). When her son, Drew, was diagnosed with autism at the age of 2 years in the spring of 1998, she became ‘‘motivated by personal pas- sion’’ to address autism, too, in particular, why children with autism do not speak (www.Gernsbacherlab. org). Since then, she has become an active researcher and professional speaker in this and related areas, as well as a public advocate for the rights of individuals with autism (e.g., Dawson, Mottron, & Gernsbacher, 2008; Gernsbacher, 2007a, 2007b; Gernsbacher, Sauer, Geye, Schwei- gert, & Goldsmith, 2008). At KU, her lecture (a paid public lecture) filled a 990-seat on-campus auditorium large- ly, it appeared, with students earning course credit. In addition, it was simulcast to 200 more students and community members at KU’s Ed- wards Campus in Kansas City. For the record, Gernsbacher had given four previous invited lectures by the same title at (a) a September, 2005, colloquium at Washington Universi- ty, (b) the August, 2006, conference on Brain Development and Learning: Making Sense of the Science (Vancou- ver, British Columbia, Canada), (c) the February, 2007, meeting of the Southeastern Psychological Associa- tion, as a William James Distinguished Lecturer (New Orleans), and (d) the April, 2007, John S. Kendall Lecture Series at Gustavus Adolphus College (St. Peter, Minnesota).
In her lecture, Gernsbacher ad- dressed several assumptions about autism’s diagnosis and etiology, for instance, that it is epidemic (Maugh, 1999); that it was once caused by emotionally cold ‘‘refrigerator moth-
ers’’ (Bettleheim, 1967); and that it is today caused by childhood measles- mumps-rubella vaccinations (Kirby, 2005). Emphasizing the importance of rigorous research methods and experimental designs, she concluded from her review of the literature, some of it her own research, that these assumptions were myths and misconceptions (see, e.g., Gernsba- cher, Dawson, & Goldsmith, 2005; Gernsbacher, Dissanayake, et al., 2005). In the final section of her lecture, she addressed autism inter- vention and therapy, specifically the assumption that applied behavior analysis is an effective treatment. Before addressing her review of this literature and her conclusions, though, I put applied behavior analy- sis in a broader disciplinary frame- work and then in a local and historical context. This material is intended, in part, as a scholarly resource, so it is a tad academic.
Applied Behavior Analysis
Applied behavior analysis is more than intervention and therapy. It is a subdiscipline of the field of behavior analysis (J. Moore & Cooper, 2003; see The Behavior Analyst; www. abaintenational.org; www.behavior. org). The field comprises (a) a natural science of behavior (i.e., basic behav- ioral principles and processes; e.g., reinforcement, shaping; see Catania, 2007; Journal of the Experimental Analysis of Behavior), (b) related conceptual commitments (i.e., philos- ophy of science; e.g., naturalism, empiricism; see J. Moore, 2008; The Behavior Analyst), and (c) applied research on problems of societal importance and means for ameliorat- ing them (Cooper, Heron, & Heward, 2007; Journal of Applied Behavior Analysis [JABA]; Behavior Analysis in Practice). For concise overviews, see Michael (1985) and Reese (1986).
Although applied behavior analy- sis arose at several U.S. and Canadi- an sites in the late 1950s and early
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1960s (Kazdin, 1978), its first institu- tional base was KU’s Department of Human Development and Family Life (established 1965), now the Department of Applied Behavioral Science (ABS; established 2004). This is where ABA’s flagship journal (JABA) was founded (Wolf, 1993), the subdiscipline’s basic dimensions were first articulated (Baer, Wolf, & Risley, 1968), and some of its earliest innovative programs of research were undertaken. These include the Juni- per Gardens Children’s Project for youth, school, and community devel- opment (Hall, Schiefelbusch, Green- wood, & Hoyt, 2006) and Achieve- ment Place for juvenile offenders (i.e., the Teaching Family Model; Wolf, Kirigin, Fixsen, Blase, & Brauk- mann, 1995), both of them in collab- oration with the Bureau of Child Research, now the Schiefelbusch In- stitute for Life Span Studies (Schie- felbsuch & Schroeder, 2006; see Baer, 1993a; Goodall, 1972).2
Applied behavior analysis involves an integration of research and appli- cation, including use-inspired basic research (i.e., basic research in the interests of application; e.g., stimulus control of stereotyped behavior; Doughty, Anderson, Doughty, Wil- liams, & Saunders, 2007), discovery research (i.e., research on unplanned findings; e.g., on the overjustification effect; Roane, Fisher, & McDon- ough, 2003), and translational re- search (i.e., the translation of basic research into practice; e.g., reinforcer
2 As for my potential conflicts of interest, I am the ABS department chairperson. Howev- er, although I have published applied research and reviews (e.g., Altus & Morris, 2004; Atwater & Morris, 1988; Morris & Brauk- mann, 1987) and am a Board-Certified Be- havior Analyst, I am not an applied behavior analyst. My interests lie largely in history and theory (e.g., Morris, 1992, 2003; Morris, Altus, & Smith, 2005). As a result, I am not deeply attuned to applied behavior analysis’s every nuance in science and practice, especially in autism, so I apologize to my applied colleagues if I am clumsy or insensitive in representing their field.
magnitude and delay; Lerman, Ad- dison, & Kodak, 2006). In the main, however, ABA addresses atyp- ical behavior (e.g., stereotypy; Reeve, Reeve, Townsend, & Poulson, 2007), methods for its assessment and anal- ysis (e.g., functional assessment and analysis; R. H. Thompson & Iwata, 2007), behavior-change procedures (e.g., desensitization for phobias; Ric- ciardi, Luiselli, & Camare, 2006), pack- ages of behavior-change procedures (e.g., self-management; peer-mediated treatments; Stahmer & Schreibman, 1992), and comprehensive programs of treatment (e.g., early intensive behav- ioral interventions; T. Smith, Groen, & Wynn, 2000).
Applied behavior analysis also ranges across several domains (Lui- selli, Russo, Christian, & Wilczynski, 2008), for instance, (a) from individ- ual procedures for specific behavior to comprehensive programs for prob- lems in daily living (e.g., Iwata, Zarcone, Vollmer, & Smith, 1994; McClannahan & Krantz, 1994), (b) from inpatient to on-site service delivery (e.g., Hagopian, Fisher, Sul- livan, Acquisto, & LeBlanc, 1998; Nordquist & Wahler, 1973), and (c) from staff training to organizational behavioral management (e.g., Mc- Clannahan & Krantz, 1993; J. W. Moore & Fisher, 2007; Sturmey, 2008; see Cuvo & Vallelunga, 2007). Finally, the field’s interventions are, ideally, research, too, in that clinical decisions are data based (e.g., when to alter or amend them). In fact, the ethical guidelines of the Behav- ior Analysis Certification BoardH (BACB) require data-based decision making (see Bailey & Burch, 2005, pp. 104–106, 212–214).
Gernsbacher’s Review and Conclusions
Gernsbacher did not review all the applied behavior-analytic re- search in autism. That would have been too great a task. Over 750 articles were published between 1960 and 1995 (DeMyer, Hingtgen, &
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Jackson, 1981; Matson, Benavidez, Compton, Paclawskyj, & Baglio, 1996) and hundreds more since then. They appear in JABA, other applied behavioral science journals (e.g., Be- havioral Interventions), and journals in related fields (e.g., American Jour- nal on Mental Retardation, Journal of Consulting and Clinical Psychology). What Gernsbacher reviewed was a subset of the comprehensive programs for early intensive behavioral inter- ventions (ABA-EIBI) that she referred to as ‘‘the Lovaas-style of behavioral treatment.’’3 Based on her review, she concluded that the effectiveness of applied behavior analysis for autism was another myth and misconception and that the gains made during treatment were due to the children’s ‘‘development,’’ not to ABA-EIBI.
These conclusions upset some au- dience members. A parent of an adolescent with autism, for whom applied behavior analysis had dra- matically improved their lives, asked me what he should use instead. An ABS major bemoaned that her course of study was apparently for naught. A faculty member criticized Gerns-
3 Equating applied behavior analysis with any one intervention, for example, with Lovaas-style ABA-EIBI or, more narrowly, with discrete-trial training (DTT), is a con- ceptual error. Lovaas’s is just one of several ABA-EIBI programs, of applied behavior- analytic programs in general, and of programs based in the science of behavior (Luiselli et al., 2008; T. Thompson, 2007a, pp. 43–46; see, e.g., Koegel & Koegel, 2006; Schreibman, 2000; Strain, McGee, & Kohler, 2001). In fact, the number of applied behavior-analytic programs is huge, limited only by the permu- tations on the number of basic behavioral principles (e.g., reinforcement, stimulus con- trol), behavioral processes (e.g., chaining, shaping), behavior-change procedures (e.g., activity schedules), and packages of behavior- change procedures (e.g., verbal behavior inter- ventions), all constrained, of course, by ethical considerations (see Green, 1999; Hayes, Hayes, Moore, & Ghezzi, 1994). Finally, although Lovaas-style ABA-EIBI is today’s best evi- dence-based treatment for autism, it may not be the best treatment. That remains an empirical question. It is also not likely the last best treatment. Science, both basic and applied, is a process; it evolves (see T. Thompson, 2008).
bacher for overlooking the extensive literature on which Lovaas-style ABA-EIBI is based. This criticism, though, was not fully justified. Gernsbacher had to be selective in her review, given the size of the literature, the breadth of her audi- ence, and the interests of time.
As for my reaction to her conclu- sions, I was stunned. However, I was stunned not so much by her conclu- sions per se. I had heard them before in antiscience rhetoric about autism’s etiology and treatment, as well as in sentiment against applied behavior analysis in general (e.g., Meyer & Evans, 1993; www.AutCom.org; www. autistics.org; see ‘‘Is ABA the Only Way?’’ at http://www.autismnz. org. nz/articlesDetail.php?id523; contra. Baer, 2005: Eikeseth, 2001; Green, 1999; J. E. Jacobson, Foxx, & Mulick, 2004; Leaf, McEachin, & Taubman, 2008; Lovaas, 2002, pp. 287–407; T. Thompson, 2007a, pp. 187–203; in general, see Offit, 2008).
Sentiment against applied behavior analysis is not, of course, necessarily antiscience. No matter what Gerns- bacher’s sentiments may be, her achievements are anything but anti- science. What stunned me, then, was how she reached her conclusions: She inaccurately represented research re- views, wrongly characterized applied behavior-analytic interventions, mis- leadingly appealed to history, inac- curately conveyed research designs, selectively omitted research results, and incorrectly interpreted interven- tion outcomes. Although misrepre- sentations are often only a minor nuisance in science, they can have harmful consequences, which I be- lieve hers did (and do), both locally and more broadly.
The local consequences included misinforming KU’s community mem- bers about ABA-EIBI; hundreds of KU students about a science of behavior and its application; current and prospective ABS majors about a course of study at KU (and careers); and KU staff, faculty, and adminis-
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THE GERNSBACHER LECTURES
trators about scholarship in a depart- ment renowned for its research in applied behavior analysis. The broad- er consequences include Gernsba- cher’s probable influence on behav- ioral, social, and cognitive scientists who teach, conduct research, and provide services in autism; funding agencies and foundations who set priorities and allocate resources for autism research and applications; and state and federal agencies that set standards for autism services and funding. She has standing and stature in most, if not all, of these venues: in APS, of course, but also in the American Association for the Ad- vancement of Science (AAAS), where she is a psychology section member at large, and in the National Science Foundation (NSF), where she is on the Advisory Committee for the So- cial, Behavioral, and Economic Sci- ences. Although Gernsbacher surely gained these highly respected positions by conducting first-rate science, the hallmarks of her science were largely absent in this section of her lecture.
In Response
In what follows, I respond to Gernsbacher’s misrepresentations, but remain agnostic, yet curious, about their source or sources. No matter what, though, misrepresentations re- main misrepresentations. In address- ing them, I reproduce this section of her lecture below,4 inserting bracketed
4 The text was transcribed from KU’s Instructional Development and Support’s digital recording of Gernsbacher’s lecture for KU’s Department of Psychology. The section on applied behavior analysis runs from about the 48- to the 55-min mark. I acquired a URL of it from David S. Holmes, a KU professor of psychology, who introduced Gernsbacher. When I asked him if I could forward it to students and friends, he responded, ‘‘You can distribute the URL to anyone who is interest- ed. In fact, I want to encourage you to do that as widely as possible’’ (D. S. Holmes, personal e-mail communication, November 27, 2007). The URL is http://merlin.cc.ku.edu:8080/ asxgen/ids/holmes/autismlecture.wmv. As for
material to provide context and conti- nuity. Then, where they occur, address the misrepresentations. For the sake of brevity, such as it is, I restrict my comments to her lecture and note her ABA-EIBI-related pub- lications only in passing (e.g., M. Dawson et al., 2008; Gernsbacher, 2003). As a result, I do not address important issues in autism research and application that she did not cover, for instance, the incomplete reporting of treatment variables in research (Lechago & Carr, in press; see Kazdin & Nock, 2003), among them, therapist competence (Shook & Favell, 1996), treatment intensity (Graff, Green, & Libby, 1998), and treatment fidelity or integrity (Wolery & Garfinkle, 2002). I also set aside the literatures on treat- ment effects on brain structure (G. Dawson, 2008; T. Thompson, 2007b), autism recovery and its mechanisms (Helt et al., 2008), and ABA-EIBI’s long-term costs and benefits (Chasson, Harris, & Neely, 2007; J. W. Jacobson & Mulick, 2000).
My response may give offense to Gernsbacher, but none is intended. I am concerned about scientific com- munication and reasoning, not about a person or persons. Indeed, my comments are made in the spirit of the behavior-analytic maxim: ‘‘The organism is always right.’’ It is not always right, of course, in a moral or factual sense, but it is ‘‘right’’ in the sense that behavior is a lawful subject matter for a science unto its own. In that science, behavior is a function of the organism’s biology, its environ- ment, and the history of their trans- actions in which organisms become
Holmes’s perspective on ABA-EIBI, his intro- ductory psychology review of it is dated (Holmes, 2008, pp. 368–370); it associates ABA-EIBI with aversive control that has not been used in decades; and it is not supported by any citations to any literature. Given its content, though, it is seemingly based on Lovaas et al. (1973), Lovaas (1987), and articles on the late 1980s aversives controversy in behavior analysis (e.g., Johnston, 1991; Sherman, 1991).
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individuals.5 Unfortunately, English grammar is not neutral in this matter. Its agent-action syntax implicates organisms as the agents of their actions (Hineline, 1980, 2003). As a result, in acquiring English, we ac- quire a philosophy of mind woven thread-by-thread unconsciously into the fabric of our lives. This philoso- phy is both inimical to a science of behavior qua behavior (e.g., mind– body dualism; Koestler, 1967; C. R. Rogers & Skinner, 1956) and a basis for counter-Enlightenment, postmod- ern critiques of it (e.g., humanistic, revelatory; Krutch, 1954; Rand, 1982). Its press (that science’s press) is worse than that for evolution in Kansas (Frank, 2004). This syntax may also make my comments appear ad hominem and bereft of compassion for Gernsbacher as a parent of a child with autism. Where this occurs, I apologize (see Skinner, 1972, 1975). ABA-EIBI’s critics are always right, too.
AUTISM INTERVENTION AND THERAPY
I now turn to Gernbacher’s lecture. I begin where she began on autism intervention and therapy:
Finally, since I’m starting to talk about intervention and therapy, I am going to go to the last section of my talk and that is the empirical evidence for claims such as this: ‘‘There is little doubt that early intervention based on the principles and practices of applied behavior analysis can produce large, comprehensive, lasting, and meaningful im- provements in many important domains for a large proportion of children with autism.’’ As you might know, the author is referring to what is known as the Lovaas-style of behav- ioral treatment for autistic children.
5 I do not mean to perpetuate the nature– nurture dichotomy, that is, the false dichoto- my between nature and nurture as indepen- dent variables, even if they putatively interact. Among the best contemporary alternatives to the dichotomy is developmental systems the- ory (Gottlieb, 1998; D. S. Moore, 2001; Oyama, 2000; see Midgley & Morris, 1992; Schneider, 2003, 2007).
At this point, I offer a seemingly trivial observation, for which I beg the reader’s indulgence. As I noted, I am curious about the sources of Gernsbacher’s misrepresentations. One means of discerning them is to address them all, no matter how seemingly innocuous, to see if any patterns emerge. I begin with first instances.
Improvements in Children with Autism
The quotation above about ‘‘im- provements … for a large proportion of children’’ was taken out of context. Its author, Gina Green (1996), qual- ified it in her next sentence: ‘‘For some, those improvements can amount to … completely normal intellectual, social, academic, com- municative, and adaptive function- ing’’ (p. 38). ‘‘Some’’ children is not ‘‘a large proportion of children.’’ Quoting material out of context is not inherently misleading, of course. Moreover, Gernsbacher could not quote ad infinitum; she had to be selective. In any event, the conse- quence was probably negligible be- cause ABA-EIBI’s effectiveness has been overstated by some of its advo- cates, too (Green, 1999; Herbert, Sharp, & Gaudiano, 2002). Many critics of these overstatements, how- ever, also support ABA, as in, ‘‘ABA is one of the most—if not the most— promising interventions for child- hood autism’’ (Herbert & Brandsma, 2001, p. 49). For an overview of applied behavior analysis in autism, see Harris and Weiss (2007).
Lovaas-Style ABA-EIBI Treatment for Autistic Children
The first ABA research on children with autism was published in 1964 by Wolf, Risley, and Mees.6 The first systematic report of Lovaas-style
6 DeMyer and Ferster (1962) were arguably the first to apply the principles of operant conditioning to the socially important behav-
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ABA-EIBI was published in 1973 by Lovaas, Koegel, Simmons, and Long. The first report of a compre- hensive ABA-EIBI program was published in 1985 by Fenske, Za- lenski, Krantz, and McClannahan. And, the first clinical trial of Lovaas- style ABA-EIBI was published in 1987 by Lovaas (see also Celiberti, Alessandri, Fong, & Weiss, 1993; Maurice, Green, & Luce, 1996).
In that trial, the experimental group (n 5 19; chronological age 5 2 years 11 months) received 2 years of 40 hr per week of one-on-one in- home ABA-EIBI from their parents and staff members from the UCLA Young Autism Project. The primary control group was a treatment com- parison control group (n 5 19; chronological age 5 3 years 5 months) that received fewer than 10 hr per week of ABA-EIBI plus community treatment (e.g., special education). This controlled for mat- urational effects—or what Gernsba- cher called ‘‘development’’—over the course of the study; any such effects would presumably have been the same in both groups. A matched secondary control group (n 5 21; chronological age 5 3 years 6 months) was drawn largely from the same population and received com- munity treatment. This controlled for selection bias and permitted a com- parison between ABA-EIBI and treatment as usual (Freeman, Ritvo, Needleman, & Yokota, 1985).
Lovaas (1987) did not randomly assign his participants to the experi- mental and control groups, as he had planned, because of ‘‘parent protest and ethical considerations’’ (p. 4; Lovaas, 2002, pp. 388–389). Instead, he assigned them on the basis of staff
ior of children with autism, but they failed to address so many of the defining dimensions of applied behavior analysis (e.g., behavioral, analytic, and technological; see Baer et al., 1968) that it probably does not warrant being called applied behavior analysis.
availability for the experimental group. This is an accepted practice in clinical research, especially if the treatment and control groups can be matched a priori or are equivalent on pretreatment measures (Baer, 1993b; Eikeseth, 2001; Kazdin, 1992). In Lovaas’s case, his groups were statis- tically equivalent on 19 of 20 pre- treatment measures, among them, their IQs, which were 53 and 46, respectively (McEachin, Smith, & Lovaas, 1993). After treatment, the experimental group had significantly higher IQs than the control groups (83 vs. 52 and 58) and a significantly higher probability of passing first grade in regular education class- rooms (9 of 19 vs. 1 of 40). The 9 participants who passed first grade had a mean IQ of 107 and were considered to be ‘‘recovered.’’ In a follow-up study, the experimental group was found to have maintained these and other gains (e.g., in adap- tive behavior; McEachin et al.).
In describing Lovaas-style ABA- EIBI, Gernsbacher continued, ‘‘as illustrated in the intro to this 1980s film.’’ The film was Behavioral Treat- ment of Autistic Children (E. Ander- son, Aller, & Lovaas, 1988), which reviewed and followed up on Lovaas et al. (1973) and Lovaas (1987). Its 15-s introduction showed a therapist and a child sitting at a table across from each other engaged in DTT. DTT is one of many technologies that has evolved from ABA research (T. Smith, 2001; Tarbox & Naj- dowski, 2008), but none of them is meant to be applied in a cookie- cutter fashion. Ideally, applications are individualized, taking into ac- count developmental and individual differences (Schreibman, 2000), as well as differences in families and settings (on values, see e.g., Wolf, 1978).
DTT ranges along a continuum from more to less structured trials and from massed to distributed trials. Highly structured and massed DTT may consist of a therapist’s request or
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instruction (e.g., to imitate a vocal or nonvocal model), a child’s response (e.g., imitation), and a therapist’s consequence (e.g., ‘‘yes,’’ ‘‘no,’’ hugs). The film’s introduction shows the end of one such trial, in which the therapist says, ‘‘O