Knowing Peter Killeen

Abstract

I completed a PhD thesis early in 1988. This thesis was about the discrimination of brief empty time intervals. In this thesis, findings were explained in terms of the properties of an internal clock (pacemaker-accumulator system), with the help of some cognitive interpretations. There was no reference to Peter R. Killeen's work in this thesis. Circulation of knowledge was not as easy as it is nowadays! And when you begin to review the existing literature on time perception in the mid 80s, you already have a century of publications on the subject to catch up on, starting with a review by Fraisse (1984) and the edited book by Gibbon and Allan (1984).

During the summer of 1989, having to prepare a first grant proposal for a Canadian agency, I had to refresh and upgrade my knowledge about time perception. My search led me to Killeen and Weiss (1987), a remarkable and comprehensive article, and I was almost tempted to quit the field because the standard of excellence was suddenly set too high! Obviously, I didn't quit but had to work for a while with the impression that I would never be able to contribute, even modestly, to this research field. That 1987 article was such a fine theoretical integration of the main pieces of information in the field of temporal discrimination, providing an integrative view that would indeed apply to any neural counting mechanism. For those needing additional explanations, after Killeen and Weiss, about the models that could be derived from a pacemaker-accumulator system, it was possible to refer to the appendix of another Psychological Review article (Killeen & Fetterman, 1988) where a timing theory, based on animal behaviors (rate of reinforcement), could also be applied to duration discrimination and other tasks or phenomena. And for those who had not yet realized that errors in temporal tasks may not only be caused by the properties of the pacemaker but also by the fallibility of the counter, an even more comprehensive description of its role, also published in Psychological Review, was soon to follow (Killeen & Taylor, 2000).

So far, so good. I prepared the grant proposal and talked with a colleague on the English side of the department that was also preparing a grant proposal for the same agency. We discussed, and, although we were not at all in the same research field (his training was on eating-related behavior of … pigeons maybe), I noted that among the few references in our proposals, we referred to a likely common author, but his references were from the 70s.1 Could there be more than one Killeen in experimental psychology? Maybe a common name; after all, there is more than one person who crossed the Atlantic from Ireland. But several P. R. Killeen in experimental psychology? No! Thinking back on it, it makes sense that this was the same person, given the content of Killeen and Fetterman and given convergence of the animal and human timing literature that followed the 1983 meeting of the New York Academy of Sciences (Gibbon & Allan, 1984).

How could one person be so influential in different fields of psychology? I was already impressed by this Killeen, but there was still much to discover about his work and about the man.

In late 1990, I received an invitation to attend a meeting on different research avenues in the large domain of time, action, and cognition. The invitation was sent to only a small group of time-related researchers and would be held in Saint-Malo, France, in October 1991 to honor Paul Fraisse who turned 80 that year (Macar et al., 1992). So far, so good. But then came the short list of attendees, which included young researchers like Miall, Boltz, Droit-Volet, and Ivry and seasoned ones like Michon, Richelle, Block, Zakay, Allan, and … the Psychological Review machine.

I met Peter Killeen for the first time at that meeting. Knowing that he and a few other foremost researchers would be there, was quite intimidating. The only consolation I had was that the meeting, being in France, curiously made me feel as if I had a home-ice advantage! I would not say I was “counting the minutes” (the title of Peter's talk) before, but I certainly was looking forward to attending his talk, which integrated a part of the literature I was familiar with (notably the work of researchers from a Canadian University, Allan and Kristofferson). It was a nice occasion to hear additional explanations about the extension of Weber's law (Killeen & Weiss, 1987) and the need to also take into account accuracy (the validity of a measure) in addition to precision (variability). I finally had the opportunity to chat with Peter, notably during the visit to Mont Saint-Michel, and I gradually discovered that there was a genuine gentleman hiding behind this die-hard behaviorist!

After Saint-Malo, I kept an eye on the work of some people that attended the meeting, including Peter's, who, with Gregor Fetterman, was continuously feeding the pacemaker-counter system with new data and analyses (Fetterman & Killeen, 1990, 1992, 1995, to name only a few). These empirical contributions should have been enough to keep a man busy and feed a CV for half a decade … but Peter was also providing theoretical contributions (see, for example, Killeen, 1992), which included a BBS paper (Killeen, 1994) that, alone, would normally require 5 years of full-time academic work! And that decade of scientific contribution was flavored with some book chapters, including the most interesting “Time's causes” (Killeen et al., 1997), organizing an understanding of timing and time perception based on Aristotle's four causes (material, formal, efficient, and final) and introducing a pseudologistic model for analyzing psychometric functions.

Because Peter Killeen writes faster than I could read English (and Greek, should I say, given the content of his work) and given that there were also other colleagues from Saint-Malo feeding the field, I had to give up following it all, but I always looked for occasions to meet him again. A colleague and I organized Fechner Day 1998 (the annual meeting of the International Society for Psychophysics) in Québec and decided to invite Peter to give the keynote address to open the meeting. In his “Fechner's magic” (Killeen, 1998), the keynote speaker analyzed Miller's magical limit and then integrated the work of several psychophysicists such as S. S. Stevens and Bob Teghtsonian.

I also invited Peter to participate in a symposium on time perception in 2000. This symposium was part of the joint meeting of the Canadian Society for Brain, Behaviour, and Cognitive Science and the Experimental Psychology Society (UK) held at the University of Cambridge. The symposium was scheduled early in the morning. I cannot report the content of Peter's talk. I simply missed it because I didn't wake up on time due to jet lag. But I can tell that later during the meeting, Peter the gentleman found the right words to stop me feeling guilty about missing the symposium and to make it possible to enjoy the rest of the meeting and go punting, with him and his wife Mary, on River Cam.

I then stayed in touch with Peter and, shortly after, for reasons I no longer remember, I gave him a hand in adding to the family tree of International Society for Psychophysics members that he was building. In the Spring of 2003 during a sabbatical leave, I had the privilege to visit Arizona State University, and Peter kindly hosted me for a month in an apartment beside his house. During this stay, I learned by observation why it was possible for him to be so productive in the last three decades of the 20th century. I understood that his discipline, his working habits, would eventually lead to the Psychological Science paper (Killeen, 2005; his response to the replicability crisis) and other Psychological Review papers (Killeen, 2009; Killeen et al., 2018), reading and writing early in the morning for a couple of hours before beginning the working day! I also noticed that on the living room table, there were no magazines about D'Backs or Cards lying around but books on the life and thought of Newton or Galileo, on the history of science, or some other light reading like that, which we all do to relax! During the stay, I remained unable to convince him to join me at a Cactus league preseason game or an NHL game, even after promising that I would explain to him the rules!

In September 2007, Peter chose to spend a few weeks in Québec, at Université Laval, and we took the opportunity to work on a few projects. This collaboration led to the publication of a few articles on the effect of space on temporal judgments (Roussel et al., 2009) and on the effect of counting when tracking long time intervals (Grondin & Killeen, 2009a, 2009b). This could well have been the last time where our academic paths would cross. But that was not the case. The Psychological Review machine would strike back!

At some moment in 2019, Peter apparently became quite unsatisfied with all the violations of Weber's law—the sacred scalar property—in the field of time perception. And probably because data showing these violations often came from my lab, he knocked at my door to propose to collaborate on a project for finding a solution to this problem. Naïve, I said yes. Yet, I was warned … I had observed the pace of the machine in 2003. I already had a happy life filled with work, joy, and projects, but I was suddenly entrained by a senior citizen in the festival of nonstop exchanges of manuscript versions.

Confinement in March 2020? Just an occasion to work even more, even faster. No time for conspiracy theory, rocking chair, or paralyzing anxiety. This exchange continued and eventually gave birth to a new theory where, in the end, it was not necessary to accommodate or predict Weber's law! But Peter's new theory consumes data. Throughout this kind of 25-hour-a-day pace of exchanging manuscript versions, I tried some “keep it simple Peter, how about AIC, think Occam, etc.”; all beautiful things I may indeed have learned from him. There were never enough data to drive the point home until the miracle occurred. Peter was satisfied, and the coauthor was exhausted!

By the end of the process, Peter had developed a new theory of perception, based on the degradation of the memory trace left by a signal, a theory that, in the paper, was applied to duration estimation. Time estimation no longer required a clock but simply the reading of the strength of the stimuli marking a time interval (Killeen & Grondin, 2022). This was sufficient to process a large amount of data that posed problems for pacemaker-counter models.

Would you believe that parallel to this breathless marathon that led to another Psychological Review paper, Peter Killeen was preparing other articles? Including one in Psychological Review (Killeen, 2023)!

A man passionate about science and an emblematic figure in behavioral research and time perception, Peter Killeen identified important questions and addressed them. He made no concessions regarding the need for psychology to be guided by science and quantitative tools. He was a thinker in the service of his discipline and, for me, a mentor and role model. Merci Peter.

Simon Grondin is the sole author of this article.

The author declares not conflict of interest.

No human or animal subjects were used to produce this article.

Data sharing is not applicable to this article, as no data sets were generated or analyzed during the current study.