BOOK REVIEWS

the basic assumptions in what one feels easily be set up in the laboratory, and at times is a crusade to purge the litera­ Crab canon the responses that the crabs use to assess ture of half-truths. Some detailed proofs shells and opponents are clearly visible and alternative derivations are left as F. A. Huntingford and easy to record. These encounters are (well-hinted) exercises for the reader. illustrated by the many exquisite photo­ The approach works well for maser Assessments and Decisions: A Study of graphs in the book. theory, which occupies the first two­ Information Gathering by Hermit Crabs. Elwood and Neil begin by defining thirds of the book. This part is not By R. W. Elwood and S. J. Neil. Chap• and discussing the basic concepts. The always easy going, but the reward for the man and Hall: 1991. Pp. 192. £29.95. term "assessment' is mainly used to de­ hard climb is a broad overview of the scribe situations in which "some aspect subject, from the theoreticians' perspec­ How does natural selection act on be­ of the environment is perceived and the tive. havioural traits? Or more specifically, information [is] used as a factor in deci­ In the last third of the book, Elitzur what are the effects of animals' be­ sion making"; 'decision-making' is used reviews the observed masers and their haviour on their fitness? In recent years to refer to "a process by which behaviou­ use as astronomical tools. This material (some might say not before time), be­ ral change is non-random". The authors will not submit readily to textbook treat­ havioural ecologists have recognized that next describe the behavioural ecology of ment, so here the author's style changes to answer these questions it is often hermit crabs and the biology of their to that of a monograph or review. The necessary to understand the mechanisms study population of P. bernhardus. The coverage is broad and comprehensive, that generate adaptive behavioural re­ scene is then set for the two main but necessarily more superficial than the sponses - in other words, to study what sections of the book in which motiva­ treatment of maser theory. Researchers causes animals to behave as they do. But tional models are developed to explain will want to consult the observational integrating studies of the causes and the crabs' shell-related behaviour. review articles that are cited, where they consequences of behaviour is not at all Elwood and Neil describe how crabs will also get a stronger taste of the easy. In Assessments and Decisions, assess the quality of an unoccupied shell, excitement of current research and the Elwood and Neil address this task, using presenting a single-factor motivational glamour and spectacle of masers. Masers data from an elegant body of ex­ model of the behavioural mechanisms are not only intellectually challenging, perimental research conducted over the involved. They then provide an account they are also fun, and this is one ingre­ past decade or so on decisions made by of the shell fights, explaining in the dient that I missed in this otherwise clear hermit crabs as they seek out and fight context of games theory the role of shell and excellent introduction. The book is over the shells in which they live . value and opponent size in decision­ an essential purchase for workers in the Hermit crabs in general (and in par­ making. The single-factor model for un­ field, and will also interest other astro­ ticular the small species such as Pagurus occupied shells is then expanded into a physicists and researchers In related bernhardus) are well suited for such two-factor graphical model. Here. a areas of physics. 0 studies. Their shell is a precious re­ crab's assessment of the value of the source, the species and size of which can contested shell and of the probable costs R. J. Cohen is at the Nuffield Radio make the difference between life and of continuing a fight determine its choice Astronomy Laboratories, )odrell Bank, death. Encounters between crabs and of responses. The authors scrutinize how Macclesfield, Cheshire SKll 90L, UK. shells, and between crabs and crabs, can well their models explain the crab's be­ haviour and describe experimental tests of the models' predictions. They con­ clude by explaining how their models go beyond others, expressing the hope that this "will result in advances in our appre­ ciation of how animals make assessments and decisions". This is a very good and enjoyable book, and the experiments are described in a clear, concise and accessible way. Elwood and Neil address an important question of general interest to behaviou­ ral ecologists and "those interested in motivational analyses" (the intended au­ dience of the book). Nevertheless. I have mixed views about whether the hope expressed at the end is realistic. Although the experiments described in the book contribute greatly to our understanding of how animals make de­ cisions, I do not feel that the models (in the graphical form in which they are Wartime Interest in radar technology and microwaves led directly to the development presented) add much to a simple verbal In 1951 of the first maser device by Charles H. Townes (middle) and colleagues at statement of the hypotheses they em­ Columbia University But the original idea also seems to have been independently body. This may well be just a personal conceived by Joseph Weber at the University of Maryland, and by Alexander M. quirk. though - it certainly does not Prokhorov (left) and Nikolai G. Basov (right) at the Lebedev Physics Institute in detract much from the book's consider­ Moscow. The field grew rapidly and involved many of the people who later developed able value. 0 the laser. This fascinating and often controversial history Is told In Jeff Hecht's Laser Pioneers, which contains 13 Interviews with the researchers who made the F. A. Huntingford is in the Department of breakthroughs. A revised edition is now published by Academic Press, price $39.95. Zoology, University of Glasgow, Glasgow G128QQ, UK. NATURE· VOL357 . 21 MAY 1992 205 © 1992 Nature Publishing Group