nature neuroscience • volume 3 no 5 • may 2000 427

Some animals live in sensory worlds thatare unimaginable to us. Bats and dolphins,which operate on fast-forward, constructcomplex neural images of the environ-ments through which they hurtle by infor-mation encoded in the reflections ofultrasonic ‘sound bites.’ Electric fish probetheir surroundings with brief electricalpulses and sense nearby objects by themicrosecond shifts in timing and micro-volt changes in amplitude these objectscause in their self-generated electric fields.Some electric fish ‘digitize’ information atfrequencies exceeding a kilohertz with sub-microsecond jitter. These are feats thatpush the envelope of ion channel behav-ior and neural processing.

Bees forage on cloudy days by detect-ing complex patterns of polarized lightin the sky. This is done with a small dor-sal patch of retina comprising a few hun-dred specialized ommatidia. The exactpositioning of a single ultraviolet-sensi-tive photoreceptor within each omma-tidium, and the variation of its positionwithin the ommatidia across the dorsalpatch, allows a bee to perceive thebrightest signal when it is lined up withand flying towards the unobservable sun.This is a simple but elegant solution bystrategic positioning of an array ofdetectors, a so-called ‘computationalanatomical’ solution.

It is awe-inspiring to consider howanimals accomplish these feats; it is noless so to trace the paths of discoveryleading from our cloistered anthro-pocentrism to the realization that manyanimals operate in a realm unknowableto us. Sensory Exotica: A World BeyondHuman Experience attempts to peer intothese private worlds and inspire us inboth ways.

classical; this is not a volume for thoseinterested in the cutting edge. Rather, theauthor dwells on the history of discov-ery, the nature of scientific investigationand the sociology of science in thesefields. He describes how these unusualsenses were first discovered and applaudsthe simple but clever behavioral experi-ments used to glimpse into an animal’smind and comprehend what we cannotdirectly perceive. He illustrates for eachunusual sensory system the movementfrom initial skeptical dismissal by fellowscientists to final acceptance by theweight of internally consistent, repro-ducible evidence. In many ways, thesociohistorical aspects of doing scienceare as much the main message of thisbook as the sensory biology of thesewonderful animals.

I found this book to be an enjoyableread, although it has its share of minorannoyances. The author occasionallywalks a fine line between enhancing thescience and distracting the reader withanecdotes and asides. The tone of thebook is chatty in places, and the quali-ty of some of the figures is pixilated andamateurish. There are the occasionalfactual errors (at least in electrorecep-tion, my area of expertise). These errors,however, would likely only bother anexpert and do not detract from the mainpoints.

As a neurobiologist, I found SensoryExotica a regrettable choice for a titlebecause it reinforces the notion of theseanimals as unusual, albeit intriguing.Luckily, in a final epilogue, the authorreunites these separate islands into thelarger Gondwanaland of neurobiologyto show how they are the exceptions thatprove the rule. He correctly emphasizesthat although these animals may havefancy transducers and high-end neuralprocessors not possessed by less-blessedanimals, in a fundamental sense they areno different from anybody else. Ratherthan being oddball, their sensory sys-tems are showcases of the exquisitedevelopment of the normal. Such senso-ry systems are not only understandablein terms of common neurobiologicalprinciples, but they illuminate them.

The world at large envisions scientistsas detectives. Burdened by grant writingand other daily chores, we often forgetthat vision. This book will rekindle thatnotion, hopefully even in the jaded pro-fessional. I recommend this book highlyto its intended audience as well as to thepracticing scientist eager to read a well-paced and relaxing book.

Exceptions that prove the ruleSensory Exotica: A World Beyond HumanExperience

by Howard HughesMIT Press, 1999. $26.95hardcover, pp 344ISBN 0-262-08279-9

Reviewed by Harold H. Zakon

This book, which grew out of anundergraduate course taught by theauthor, is not a textbook but a popularscience book. It is at the level of a com-panion book for an introductory college-level course in sensory biology orperceptual psychology, or for the inter-ested non-scientist. It is generally wellcrafted, clearly written and engaging. Thebook includes sections on echolocationby bats and dolphins, electroreception byelectric fish, magnetoreception in a vari-ety of animals, ultraviolet light and polar-ized light reception in bees and ants, andpheromone reception in mammals andinsects. Included in this last section is anoverview of the evidence for the sensitiv-ity of our own olfactory vomeronasalorgans to putative human pheromones.This section is intriguing because itemphasizes the surprising fact that weourselves possess sensory capacities thatare beyond our direct perception.

Although this book is aimed at anon-technical audience, the author doesnot shrink from explaining some fairlytechnical points. His explanations ofmathematical or physical principlessuch as Fourier analysis, vector addition,the electromagnetic spectrum andpolarization of light are lucid and vivid.His descriptions of complex biologicalphenomena such as Doppler shift com-pensation in bats, the jamming avoid-ance response of electric fish, or therelationship between photopigment ori-entation, photoreceptor organizationand polarized light perception arecogent and approachable. Moreover, hedoes this without getting bogged downin detail or lessening the reader’s senseof wonder for the abilities of these ani-mals and the mechanics of their sensorysystems.

With a few exceptions, such as adescription of recent experiments iden-tifying a plausible magnetoreceptor,most of the work cited in this book is

book review

Harold Zakon is in the Section of Neurobiology& Institute for Neuroscience, University ofTexas, Austin, Texas 78712, USA.e-mail: h.zakon@mail.utexas.edu

© 2000 Nature America Inc. • http://neurosci.nature.com©

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