In Honor of Henry S. Pennypacker, 1937–2023

Hank Pennypacker had an inestimable influence on the development of the science of behavior; the establishment and promotion of behavior analysis as a cohesive field and profession; the foundations, health, and vigor of the behavior analysis program at the University of Florida; and the achievements of the many students and colleagues whose lives and careers he inspired, including my own. I had the great good fortune to be part of Hank's research and development team while a graduate student during the early to mid-1980's, as the analyses and syntheses that would give rise to MammaCare were unfolding. This period arguably merits a closer look in our honoring of Hank, for it represents a genuine microcosm of his legacy as a scholar, a teacher, and as a person.

Hank often emphasized the power of one's initial experimental question in shaping a program of study. For this particular program, the origin story lay in the observation that a majority of breast tumors were being found first by women themselves rather than through screening technologies such as mammograms or ultrasound. Sadly, by the time the tumors were identified, they were often large and, if cancerous, advanced. Hank's question thus emerged: If fingers could become proficient with the complex discriminations required to read Braille, shouldn't it be possible to help women learn to detect small masses, at a point when treatment was much more effective? For the next 50+ years, Hank accepted the challenge this question entailed. To begin to address it, he turned first to his roots in classic experimental psychology. (Hank's PhD work involved highly controlled laboratory investigations of classical conditioning in monkeys, and he was known to describe himself as a “converted Hullian.”). Here, a series of careful psychophysical studies detailed that the tiniest of ball bearings embedded between silicon pancakes could be reliably reported when fingers were placed directly over the target (e.g., Adams et al., 1976), clearly demonstrating the proof of concept.

Of course, ball bearings are not breast tumors, and the need for a more realistic simulation of breast tissues resulted in an ongoing collaboration with materials scientists to develop a medium appropriate for discrimination testing and training. Hank frequently argued for the importance of working together with other disciplines when attacking big problems, and here was an initial case in point for the breast-examination project. With his legendary insistence on absolute units, critical dimensions of real breast tumors and normal nodularity were measured and approximated in silicone in an iterative process that resulted in increasingly sophisticated breast models containing lumps of varying size, firmness, and depth of placement (e.g., Madden et al., 1978). When skeptics (usually physicians) commented that the silicone models didn't feel exactly like the real thing, Hank liked to quip that an outstanding feature of the flight simulators relied on to train pilots was that they never left the ground! (Among his many skills and interests, Hank was also a licensed pilot.) It was only necessary that the models capture characteristics central to the target discrimination between normal nodularity in breast tissue and tumors—and that they did. Indeed, the models provided for a more complete understanding of the psychophysics of the task; tumor detection proved to be a function of multiple dimensions (i.e., size, firmness, depth within the breast tissue, e.g., Bloom et al., 1982). In doing so, they also provided a platform for identifying the contributions of skilled behavior to tumor detection.

By this point in the research story, Hank had turned attention to a definitive behavioral task analysis. How exactly should the fingers be held and moved to ensure contact with and detection of breast masses? A series of experimental analyses was conducted to isolate each component of breast-examination skill and test which of its variants would yield the greatest number of lump detections in the silicone models and/or the most thorough coverage of the breast tissue. By way of examples, we learned that the flats of the middle three fingers, held together, were the most sensitive and that moving the fingers in small circles with varying degrees of pressure at each location examined were the optimal palpation techniques for finding the simulated masses (e.g., Stephenson et al., 1979). Similarly, a systematic linear pattern of search was superior to alternatives in thoroughness of covering the entire breast area (Saunders et al., 1986). Our confidence in identifying these critical skill components was made possible by Hank's steadfast focus on measurement, which necessarily took some creative turns given the subject matter. To illustrate, exam thoroughness was evaluated by projecting a numbered grid across a supine woman's upper torso via a slide projector on a stand. The projection was then adjusted such that each square of the grid was exactly 1 in, and the number of palpations made in each square during a woman's self-examination was recorded. Areas that went unexamined were captured perfectly, and the resulting record allowed for precise feedback. Observers were calibrated frequently. A central tenet for Hank was that behavior analysts are equipped to take on the most important of social problems because we know how to define, measure, and train behavior, which takes us to the next phase of MammaCare development.

Hank was a teacher, to his very heart—a shaper of behavior par excellence. He had an infectious excitement about the very process of behavior change. This quality has been widely heralded with respect to his classroom teaching, his mentoring, and his influence on Precision Teaching, but it was also the foundation of the breast self-examination teaching system that became MammaCare. As individual skill components were identified in laboratory studies, they were synthesized and incorporated into a targeted, individualized training program for sensitive and thorough examination proficiency. The training package ultimately involved sequential and ongoing practice of each skill component by the learner, first on silicone models and then on herself, with instructions, modeling, prompting, and immediate feedback at each step from lump detection in the silicone models and from a qualified trainer. The training package was developed iteratively and evaluated continuously in terms of culminating final rates of lump detection and thorough self-exams. Even early versions of the training were effective in increasing lump detections (Hall et al., 1980), and the package continued to improve with additional study (e.g., Pennypacker et al., 1982; Pennypacker & Iwata, 1990).

In case it's not obvious by now, Hank was always a big-picture systems-level thinker, as he made evident repeatedly throughout his career. Why write a few papers on measurement and research approaches when you can coauthor a definitive treatment for the field (Johnston et al., 2020)? Why design a few college courses when you can establish an enduring and influential university-level personalized system of programmed instruction? And why be content with improving skills in study participants when you can create a life-saving technology that is available worldwide? The next chapters of the MammaCare story take exactly the latter bent. Armed with a proven teaching system, the question became how best to get it into the hands of women and those who provided for their care while maintaining its quality. Hank was convinced that the private sector could be leveraged to aid in the process of dissemination (e.g., Pennypacker, 1986) and that behavior analysts, in general, took too little advantage of this possibility. Working toward that end became the strategy. Steps included founding a corporation; offering public stock; establishing free-standing and hospital- or medical practice-based training centers with credentialed instructors who had completed a week-long practicum at MammaCare headquarters in Gainesville, Florida; and transferring the teaching program to video-based and then computer-based presentations with automatic feedback that first underwent iterative testing until training outcomes matched those of one-on-one personal training. Today, MammaCare affiliates are located in medical and research centers across the United States, Europe, and the Middle East, and instructor certification programs are ongoing, as are sales of the training package kits. At the same time, research and development has continued to expand the teaching program for instruction of clinical breast exam skills conducted by medical students, residents, nurses, and physicians (e.g., Pilgrim et al., 1993), where its effectiveness continues to be demonstrated to this day.

This brief history of MammaCare has been recounted here because I believe it to be revealing of Hank's legacy—in terms of both its particular accomplishments and in the broader illustration it provides of his manner of leadership within behavior analysis. Hank led by doing, by showing how. And he showed us much. The model he set and the lessons he taught were powerful. They influenced the field as well as the lives of his students and colleagues, and they are as important today as ever—perhaps even more so. Hank entertained no distinction between basic and applied behavior analysis, in spirit or style or conceptual foundations, and his many successes followed from that position. Hank was never afraid to learn by trying—to emit behavior for shaping—and he expected no less of his students and colleagues. If things didn't go quite as planned, Hank's implied counsel was to “rub some dirt on it” and try a better approach. Working with Hank was always an adventure, full of shared wisdoms and witticisms, opportunities, encouragements, and challenges to take the next step. He provided a lasting reminder that we should take our work seriously but not ourselves and that enjoying what we did and who we did it with was paramount. Hank had a wide-ranging intellect and set of interests, a keen curiosity about people and the world, and a mischievous sense of humor. He loved music and travel, a shared laugh or good story and, especially, his wife and family. His was a life well-lived, and our lives are better as well for having had time with him.

Hank was also deeply concerned with the strategies that might ensure our survival as a field. He helped us to appreciate a shared responsibility for service to behavior analysis, and he lived that responsibility in prominent leadership positions until the day of his untimely death. May we all take lessons from Hank's legacy and each do what we can to honor those lessons with our actions. He would wish it no other way.