Animal Signals

Preface

Oren Hasson

Pages under the title Animal Signals are aimed mainly at academic animal behaviorists and behavioral ecologists. The "Publications" link gives a full list of my publications. I have also included part of my correspondence with the late John Maynard Smith about animal signals. These are long letters, and I hope they will be of interest to professional behaviorists; their original purpose is explained below.

In my field, I have admired Amotz Zahavi: first, as a young student, for his superb skills as a field ornithologist, and later for his great biological insight, his creativity, and his tenacity in defending his analyses of animal communication. I then came to admire John Maynard Smith for his talent, for the depth, breadth and impact of his scientific contribution, and most of all for his integrity.

I had a few disagreements with both Zahavi and Maynard Smith, though none of them were, in my eyes, truly fundamental. Amotz Zahavi did not accept the notion of amplifiers as signals distinct from handicaps. Although we agreed in many ways on how reliability governs biological signals, he held that amplifiers are handicaps and that there is no need to distinguish the two. Respecting Zahavi greatly for his influence on the way I think about animal communication, and knowing exactly where our disagreement lay (see, e.g., Hasson 1997), I stopped being troubled by it. John Maynard Smith and I, on the other hand, shared the view that signals need not be handicaps in order to be reliable, but we disagreed, for a while at least, on the distinction between amplifiers and indices. I thought we also agreed on the definition of "signals" (Maynard Smith and Harper, 1995), but John and Harper somewhat changed their minds and used a slightly different definition in their book, Animal Signals (2003).

When I met John Maynard Smith on the first day of the Behavioral Ecology Conference in Hawaii, 1995, I introduced myself (we had briefly met a few years earlier, and had corresponded a fair amount), and he said: "Ah, Oren, we need to talk." So that evening we sat in a Thai restaurant: John, his wife Sheila, Patty Gowaty (Patricia Adair Gowaty, a mutual friend and colleague), and myself. After we ordered, John turned to me and asked:

"Well, Oren, you and I understand communication better than anyone else in the world. Where do we conflict?"

Heck, we did?

Patty Gowaty, my dear friend, looked like she was having a stroke. I was both a little embarrassed and a little amused, for several reasons. The first: this is John Maynard Smith. The second: I had no idea we were in conflict.

I knew that John, as an editor of the Journal of Theoretical Biology, had read my 1994 paper "Cheating Signals", which gives a first general outline of my view of animal communication, and I suspected he mostly liked my definitions of communication, signals and cues. I did not yet know of his paper with Harper (Maynard Smith and Harper 1995), published that same year as a reply to my 1994 paper. My next thought was that I was probably the only person in the world who could have heard such a sentence from both John Maynard Smith and Amotz Zahavi, though I did not think Zahavi would ever put it in so many words. And then the arrogant little devil within me whispered: "But what does he mean by 'you and I'? Of course YOU (me) understand communication better than HE does." I kept the little devil quiet. In truth I did not quite know what to say, since I did not yet know exactly what John thought about communication. I only knew enough to believe we had a general agreement to begin with. So we ate shrimp, or whatever it was, instead.

I read Maynard Smith and Harper (1995) only later, and explained our differences in view in Hasson (1997), which presented a general model of animal communication. It too was published in the Journal of Theoretical Biology, again with John Maynard Smith as the handling editor.

Then came the monumental book by Jack Bradbury and Sandy Vehrencamp, "Principles of Animal Communication". By then I had left academic research and had no time for writing papers. But John Maynard Smith drew me back into it, in a way. He and Harper admired Bradbury and Vehrencamp's book but wanted to strengthen its theoretical framework, where they thought it was weak. In May 2000 John sent me a letter asking me to clarify a few issues, as he had asked of a few other people he valued in the field. This began a correspondence of three long letters from each of us: the first in John's own handwriting, then two typed letters. The book, Maynard Smith and Harper's Animal Signals, was published in November 2003. On April 23rd, 2004, Nils Chr. Stenseth and Glenn-Petter Sætre published a review of it in Science. The timing was painful: John had died only a few days earlier, on April 19th, 2004. I knew he had been ill for some time, but I felt that a kind giant had fallen. On the whole, Stenseth and Sætre praised the book, with one major exception: they objected to the authors' choice of using the term "index" for signals that I had defined, in my 1997 paper, as two distinct types, amplifiers and indices. They argued that merging the two was misleading and unwarranted.

I do not wish to reopen this debate by repeating arguments I have already published. But the length of my correspondence with John, until he came to see the distinction, stayed with me. I took it mainly as my own failure to be clear enough, and I was moved by the effort he was willing to make to understand something he thought important. I have decided to use this website, and the fact that my crows may draw some of my colleagues here, to present my side of our correspondence from the summer of 2000. I have not reproduced most of John's letters. They were kind and inquisitive, though the first two also showed his honest frustration as he worked to understand me; that effort can be felt indirectly through my own replies. For his last letter I give a summary of his conclusions, in my own words, with a few of his own phrases kept in quotation; his final decisions on the matter appear in his and Harper's book. My own letters I show exactly as I sent them, and I ask the reader's patience with my English: they were long letters, written in a hurry.

There was an aftermath. In 2006, two years after John's death, David Harper returned to the question in a memorial essay, "Maynard Smith: Amplifying the reasons for signal reliability" (Journal of Theoretical Biology, 2006). He acknowledged that in their 2003 book they had used "index" more broadly than I had in 1997 – broadly enough to absorb what I had kept separate as amplifiers, attenuators and indices – so that their stated aim of bringing "order out of chaos" had, in his words, gone awry; in fairness, he added, their broader usage followed their own 1995 paper and Enquist's "performance-based signal." He credited Stenseth and Sætre for noticing the missing "amplifier," allowed that amplifiers "may well be an important category of signalling components," and discussed their effects along the lines of my 1997 paper, citing our jumping-spider work on Plexippus paykulli as a signal "reliable by design." He did not declare the terminology finally settled, but it was an honest and generous reckoning.

Amotz Zahavi passed away on May 12th, 2017. Despite some disagreements I had with him, mainly with details related to formal representation of ideas, I cannot express in words his infuence on my evolutionary thinking

Correspondence: behavior [at] orenhasson.com