Debating about Animal Signals & Communication

Oren Hasson

Letters to John Maynard Smith: Preface

Pages under the title Animal Signals are aimed mainly at the academic animal behaviorists and behavioral ecologists. The "Hasson's Publications" link provides a selected list of my papers on animal communication. I have also included parts of my correspondence with the late John Maynard Smith about animal signals. These are long letters, I hope they will be of interest to professional behaviorists, and 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, for his creativity and for his tenacity in his conviction in his analyses of animal communication. Then I learned to admire John Maynard Smith for his talent, for the depth, breadth and impact of his scientific contribution, and then mostly for his integrity.


I had a few disagreements with both Zahavi and Maynard Smith, though none of them were, in my eyes, really fundamental. Amotz Zahavi does not like the notion of Amplifiers as signals. Although we agree in many ways on how reliability controls biological signals, he nevertheless believes Amplifiers are Handicaps, and that there is no need to distinguish one from the other. Respecting Zahavi tremendously for his influence on my way of thinking about animal communication, and knowing exactly what is the point of disagreement (e.g., see Hasson 1997), I stopped being troubled by it. Both John Maynard Smith and I, on the other hand, shared the view that signals may not be Handicaps to be reliable, but disagreed, for a while, at least, on the distinction between Amplifiers and Indices. I thought we also agreed on the definition of “signals” (in Maynard Smith and Harper, 1995), but JMS and Harper somewhat changed their mind, 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, but corresponded quite a bit), and he said: “Ah, Oren, we need to talk.” So, on that evening, we sat at a Thai restaurant, John, his wife Sheila, Patty Gowaty (a mutual friend and colleague) and myself. After ordering food, 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, I did not know we did! So I found this statement both a little embarrassing and a little amusing for a number of reasons. At the time, I knew he read my paper, “Cheating Signals”, 1994, which gives a first general outline of my view on animal communication. I suspected he mostly liked my definitions of animal communication, signals and cues. I did not know of his paper with Harper (Maynard Smith and Harper 1995), which was published on that year, and came out as a reply to my paper 1994. Then, the second thought that crossed my mind was that I was probably the only person in the world who could have heard such a statement from both John Maynard Smith and Amotz Zahavi, though I did not think Zahavi will express it in so many words. Then, the arrogant little devil within myself whispered to me: “But, well, what does he mean by ‘you AND I’?” – Of course YOU (me) understand communication better than HE does.” So I kept my little devil silent, but did not really know what to say, as I did not know exactly what he, John, thought of communication. I only knew enough to believe we have a general agreement to begin with. So we ate shrimps, or whatever it was, instead.


I read Maynard Smith and Harper (1995), only later, and explained the differences in view in Hasson (1997), which provided a general model on animal communication. Then came about the monumental book by Jack Bradbury and Sandy Vehrncamp, “Principles of Animal Communication”. At this time I was already banned out of academic research, needed to work, and had no time for writing papers. However, John Maynard Smith dragged me back into the business, in a way. He and Harper liked Bradbury and Vehrencamp book, but wanted to improve its theoretical framework, where they thought it was weak. On May 2000, John sent me a letter, asking me to clarify a few issues, as he did with a few other people he appreciated in this field. This started a correspondence of three long letters by each of us. The first was JMS with his own handwriting, then two typed letters. The book, by Maynard Smith and Harper, Animal Signals, was published on November 2003. On April 23rd, 2004, Nils Chr. Stenseth and Glenn-Petter Sætre published a review of this book, in Science. As it turned out, the timing was unfortunate. John passed away only a few days earlier, on April 19th 2003. I knew he had been ill for some time, but felt that a kind giant had fallen. Overall, Stenseth and Sætre praised JMS and Harper’s book (here), except for one major criticism. They seriously objected the authors’ choice of using the term Indices for signals I defined, in my 1997 paper, as two distinct signal types, Amplifiers and Indices. They claimed that combining these two was misleading and unwarranted.


I do not wish to continue this debate by repeating arguments I have already published in a number of papers. However, my long correspondence with John Maynard Smith, till he understood my distinction, troubled me. If it took JMS so much time and effort to see the difference, then I must have not been clear enough explaining myself. I appreciated JMS for his pain in trying to understand me, and for the effort he was willing to make trying to understand something he thought was important. I have decided to use the opportunity of having this website, and the fact that my crows may attract some of my colleagues, to include here my side of the correspondence with John, during summer 2000. I have not included most parts of JMS’ letters. They were kind, inquisitive, but the first two letters clearly showed frustration. Nevertheless, John’s struggle to understand me may be indirectly inferred from my own letters and my own frustration. However, I have included here most of JMS' last letter in this correspondence, with his conclusion. His final decisions about this issue are found in his and Harper’s book. I show here my letters exactly as they were sent to JMS, and I apologize for errors in my English. These were long letters written in a hurry.



Hasson O 1994. Cheating Signals. Journal of Theoretical Biology, 167: 223-238.

Hasson, O 1997.  Toward a general theory of biological signalling.  Journal of Theoretical Biology 185: 139-156.

Maynard Smith J & DGC Harper 1995. Animal Signals, Models and Terminology. Journal of Theoretical Biology, 177:305-311.

Maynard Smith J & DGC Harper 2003. Animal Signals. Oxford University Press.

Stenseth NC & GP Sætre 2004. Why Animals don't Lie. Science, 304: 519-520.