_Much of Don's research was guided, implicitly or explicitly, by the notion of a developmental cusp, whether in his examination of the acquisition of imitation in young children, the teaching of generative language to people with developmental disabilities, or in his research on self-instruction. In each of these cases, he was certainly interested in how these skills might be developed and explicitly taught. Of greater interest to Don, however, was what additional things acquiring these skills meant for someone's future. What might a child who is taught to imitate, for example, now be able to do that previously was not possible? One possibility is that a child who has been painstakingly taught to imitate now has the ability to acquire new skills rapidly simply by being exposed to demonstrations by a more competent model, under the right conditions, of course. In his research, Don was always searching for a free lunch. It is a testament to his judgment that he often found one.
_The examples of developmental cusps that Don most often gave were of behaviors or skills. There are, of course, other types of developmental cusps, such as events in a person's life. Don was one in my life. Our meeting was almost by chance. I was a new graduate student in a clinical program, battling to understand and accept abstract theories about why humans behaved the way that they did, especially because the theories had little empirical support and even less agreement among them. I was clearly losing the battle, if not of understanding then of acceptance. Then I heard Don talk at one of the proseminar meetings, the talks that all graduate students were expected to attend but rarely did. Don was then a young assistant professor, soon to be an associate professor, and he presented an elegant view of human behavior that provided a clear empirical basis not only for understanding human behavior but also for improving it. Equally important, he offered a way of testing and evaluating his and my own ideas in an empirical way. I was enthralled. And so, I approached Don and asked if I could work with him. He readily agreed, much to my surprise. It was a life-changing event for me.
_Don was a wonderful adviser. He was wise, he was encouraging, and he was supportive. He gave me superb advice. I followed most of it, some of the time. And, when I did not follow his advice and got into a lot of trouble, he was marvelously forgiving, assuming, I suppose, that the natural consequences of my behavior were much more effective than his disapproval. Equally important, Don gave me many, many opportunities to do interesting things. He was, therefore, one of the earliest proponents of the "keep them as busy as possible doing what you want them to do so that they will not have time to do anything bad" theory of behavioral intervention.
_Being advised by Don was the developmental cusp that not only helped start me on a path of intellectual discovery but also helped me throughout my career. He was the developmental cusp for many, many other people as well. There was a celebration of Don's career, organized by Karen Budd and Trevor Stokes, that took place only a few weeks before his death. Over 100 people attended, many coming from long distances to be there. Many were his academic sons and daughters - the people he had advised, mentored, and helped initially when they were graduate students and then later when they became colleagues. These academic sons and daughters had themselves produced academic sons and daughters, and these yet more academic sons and daughters. The number is literally in the hundreds. That there are so many academic descendants, and that so many came to honor him, is a testament to his influence. What they had to say about and to him was an even greater testament to the critical role that he had played in their lives and in their development as professionals and as people. Here are some of the things that others and I found so endearing and helpful about Don.
_The first was Don as a searcher for "truth," as elusive a concept as that might be. Don searched for truth in his research, in his students' research, in his discussions with others, and literally in his examination of all things presented to him. Who can forget Don sitting in the center of the first row in the proseminar room in Human Development and Family Life at the University of Kansas? Who can forget Don asking of a speaker, "Why?" or "How do you know that?" with his characteristic quizzical expression. When I first became acquainted with Don, I thought that maybe he asked the questions to point out to speakers the flaws in their logic, or their data measurement, or their experimental design. Or, perhaps, I thought, he wanted his questions to illustrate to students not to make this mistake - the one the speaker was making. I soon became disabused of these notions. The reason Don asked questions was quite straightforward. He simply was interested in the answer. He really wanted the other person's approximation of the truth. You could tell. Sometimes an answer from a speaker provoked the next question from Don and the answer to that the next question from Don and so on. But, sometimes an answer was given and Don would suddenly smile and nod as if to say, "Yes, that's good. That answers my question." Through prolonged observation, I even induced a rule. There were some answers that evoked additional questions, and there were some answers that evoked a smile and a nod, and, on rare occasions, there were answers that evoked a smile and two nods. Two nods were better than one, and one was very much better than another question.
_Of course, many people can ask the question "Why?" though rarely in such an engaging way as Don did. But Don equally asked the more positive, optimistic question, "Why not?" "Why can't we teach a person who does not yet talk to talk?" "Why shouldn't we go ahead and try to change the environments of young children so that they will display more creativity?" "Why would we assume that this person with a developmental disability could not learn to do the same things that many of us do?" The optimism of this question, "Why not? Why not try to do it?" had an enormous impact on Don's students and on the entire field. It helped lead to much of the progress that we have made over the past 40 years.
_Second, Don was a colleague and friend. Simply put, he was magnificent. You could go to Don and get his help, willingly and cheerfully given. He had the marvelous ability to help people analyze a problem, and to do it in a way that often led to a useful solution, whether it was a research problem, a problem in logic, or a problem in creating a written description of an abstract concept. He liked problems, and he was very good at helping you solve them. Equally important, Don knew his limitations, and he was careful not to exceed them, particularly at your expense.
_For a long time, Don had a sign on his office door that read "Word Merchant." He displayed that sign with pride and pleasure, though it was a bit misleading. He was not a merchant of words. He did not sell words; he gave them away. And they were marvelous words, put into elegantly constructed sentences, strung together to make clear and important points. He was the best word merchant I have ever seen in our field. And, to any who asked, he gave them away with a smile and an encouraging word or two. And, as good as the words were, just as good were the pauses between the words. In these pauses, Don did something highly unusual for word merchants - he listened. He listened to our problems, he listened to our ideas, and he listened to our aspirations. And, he responded, sometimes with humor, sometimes with logic, sometimes with questions, but always in a way that encouraged us to return with more problems, better ideas, and higher aspirations. How could one ask for a better colleague and friend?
_Lastly, Don was the consummate academician. Don was born to thrive in the halls of academia. Sometimes I imagined that Don came out of the womb clutching a cap and gown in one hand and his PhD hood in the other. He was a relentless seeker of truth; he reveled in the thrust and parry of academic debate; and he delighted in talking with and teaching students. But these were the obvious things. That Don was born to be an academic was also evident in much more idiosyncratic ways. Who else but Don would celebrate his marriage to Elsie Pinkston, not by holding a reception or hosting a party, but by organizing a symposium? And the guests were expected to give formal presentations on topics such as "marriage" and "love" and their possible causal relationship.
_A few short weeks preceding his death, we celebrated Don's career. The celebration was disguised as a professional conference with formal presentations on generalization and rules of evidence, together with discussion and rebuttals. I suspect that Don wanted a celebration of his career in this form for two possible reasons. One was that he was essentially a shy person, and he thought that he could deflect any undue expressions of appreciation and respect on the part of the people he had mentored by this facade of a professional conference. The other reason, equally probable, was that Don never really expected expressions of appreciation and respect, let alone love. But for whatever the reasons that he promoted this disguise of a conference, it didn't work. He got appreciation, respect, and even love. I am very happy he did, and I am very happy we did.