Evolution and Human Behavior 31 (2010) 75–77

Book Review

Neither evolution nor revolution—A review of TheVision RevolutionM. Changizi (Ed.), The Vision Revolution: How the LatestResearch Overturns Everything We Thought We KnewAbout Human Vision. Dallas, TX: BenBella Books; 2009.ISBN: 978-1933771-66-3 (215 pp, US $24.95 hardback)

When we think of what behavior, if any, makes usdistinctly human—of what do we think? One might beinclined to think of our ability to plan ahead or our complexlanguage, religion, and culture. However, if we look at themost phylogenetically recent structure responsible forgenerating behavior, the cerebral cortex, we find that thevast majority of ours is dedicated to the interpretation ofsensory information, the vast majority of which is dedicatedto vision. Oddly, while we have books on the evolution ofdecision-making, language, religion, and culture, few bookson the evolution of visual perception exist. The stated goal ofThe Vision Revolution is to explain the origin of select visualperception mechanisms.

The Vision Revolution byMark Changizi targets a generalaudience and describes four visual mechanisms. The authorlikens each proposed mechanism to a power worthy of asuperhero as ameans to emphasize the importance of the tasksperformed by the proposed mechanism. The book consists offour chapters, each highlighting a different visual element.

Chapter 1 explains Changizi's assertion that color visionevolved primarily or solely in order to detect emotional statesof other humans (and that this also occurred in otherprimates). His hypothesis relies upon an additional assertionthat skin evolved systematic color changes that correspond todifferent emotional states and that these color changes arehighly visible. He suggests that skin tones appear to have nocolor (to members within race) and that skin tones can“dynamically acquire any hue at all” (p. 20). Changizisuggests that his ideas counter most of the commonlyproposed reasons for color vision, one of which is theincreased ability to detect food sources.

Chapter 2 explains Changizi's assertion that human eyelocation, with two forward-facing eyes spaced apart, evolvedprimarily in order to be able to see through leafyenvironments. His hypothesis relies on an additionalassertion that eye location evolution occurred in leafyenvironments with leaves of specific sizes (i.e., no widerthan the interocular distance) and where such clutter was

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costly to not be able to see through. He suggests that his ideascounter most of the commonly proposed hypotheses for eyelocation. One such hypothesis reflects predator–preyrelationships, wherein it is better for prey species to havewider fields of vision granted by eyes on the side of the headand it is better for predator species to have enhanced depthperception granted by two forward-facing eyes.

Chapter 3 explains the hypothesis that perceptualmechanisms interact not with the current environment butwith a prediction of the future state of the environment. Thisreasoning relies on the hypothesis that most, if not all,behavioral mechanisms respond too slowly in order to reactappropriately to a quickly changing world. From this,Changizi proposes his “grand unified theory” (p. 112) ofillusions. He theorizes that all illusions discovered over thehistory of vision science are byproducts of mechanisms thatevolved in order to predict future states of the environment.The author suggests that his theory counters the manyalternate theories for all visual illusions.

Chapter 4 explains Changizi's assertion that humans canread because written letters or characters resemble features ofnature that we have evolved to perceive well. His hypothesisrelies on the frequency of certain visual features in nature,how well humans perceive these features, and the presenceof such features in written languages. He also briefly outlinesan idea of visual software programs and ultimately suggeststhat writing provides long-term programmability for humanbrains, which were “barely programmable calculators” priorto the advent of writing (p. 205).

1. Critique

Lack of citations outside of the one or two of the author'swork per chapter, serious errors in communicating (andpotentially understanding) vision and evolution research,and a great deal of conjecture by the author make it verydifficult to recommend The Vision Revolution.

Although Changizi mentions a small number of otherresearchers in passing, the book has no citations outside ofhis own sparse work. It is difficult, even for an informedreader, to determine if Changizi is writing about his personalbeliefs in a non-peer review format or if the ideas haveempirical support. This is especially problematic, given thatthe author's ideas are often mutually exclusive with current

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research as well as his assertion that his (sparse) research“Overturns Everything We Thought We Knew AboutHuman Vision,” the subtitle of the book.

Changizi's communication, and potentially his under-standing, of both vision science and evolution reinforce animpression of personal conjecture. For example, the author'sdiscussion of color vision lacks several topics essential to thearguments that he makes, such as trichromacy, additiveversus subtractive color mixing, and color constancy.

These gaps in vision research generate important errors.For example, Changizi outlines his idea that sex differences incolorblindness evolved adaptively in order to enhancemothering (p. 33). However, at no point does he communicateany understanding that such sex differences are predomi-nantly a genetic byproduct. It is well known that the genes forlong- and medium-wavelength cones reside predominantlyon the “X” chromosome and that males are more oftencolorblind because having only one copy of the “X” givesthem just one chance to not inherit a flawed or absent copy ofthese genes. It is difficult to see how the circuitous andimplausible genetic rearrangement required in order tosupport the author's adaptive reasoning could take place.

Unfortunately, Changizi also communicates a misunder-standing of evolution and how to test evolutionary hypotheses.For example, he selected computer-generated “commercialpark” images in order to determinewhat kind of visual featureshumans evolved to see. Such images are obviously evolu-tionarily novel and the author leaves ambiguous theevolutionary relevance of any additional images.

This unfamiliarity with evolution surfaces throughout thetext primarily as a sprinkling of evolution on top of theauthor's conclusions. For example, when he states “Thatvisual signs and symbols for both objects and words haveculturally evolved to look object-like is a fundamentalobservation,” (p. 194), or that the Pleistocene epoch'sHeimlich maneuver was rapid upside-down shaking (p.33–34). The author states these ideas as fact without citationor explanation.

Changizi unfortunately appears to endorse Panglossianadaptationism. He states that the default presumption shouldbe that any given trait is adaptive and that to assumeotherwise indicates a lack of being sufficiently clever (p.114). He states that nonadaptive explanations should only beconsidered if they stem from “a really good argument, withevidence” (p. 114) but suggests no such standards for anyadaptive explanation. Indeed, the author practices such anapproach throughout the text, such as his just-so reasoningfor colorblindness sex differences without consideration ofgenetic constraints.

This approach and reasoning of the arguments unfortu-nately produces questionable logic for Changizi's ownarguments. For example, he suggests in Chapter 2 that onereason that predator–prey relationships do not well explainthe location of eyes is because they rely on the existence ofthe trait in an ancestor (how this is a detriment to such anexplanation is left unstated). However, on the same page of

the text, he argues support for his own hypothesis based onhumans having ancestors who loved leaves and leafyenvironments (p. 90).

This type of logic characterizes Changizi's arguments ineach chapter. For example, he bases his assertion in Chapter4 (i.e., that letters resemble the features in the environmentthat we evolved to see) on methods that may support theopposite of his hypothesis. In this chapter, Changizi outlineshow he gathered data from two undergraduates (researchassistants that he trained) who looked for features (that heselected) from images (that he selected) in order to findcertain types of line intersections (that he selected). He thenfound moderate overlap between the frequency of suchintersections and the frequency of parts of a small subset(roughly eight English letters) of some characters (that heselected) in a few languages (that he selected). Despite thishighly subjective process resulting in little supporting data,the author concludes that “letters, and therefore the wordsthey form, look like objects in nature” (p. 188). While it istrue that eyes evolved to see natural features and that writtenlanguage is visible to us (indeed, nothing else is possible),Changizi's data may actually support the opposite of hisconclusion. Given that even highly subjective methods wereonly able to imply moderate correspondence with a minorityof letters suggests that the majority of written languagefeatures characters that stand out from natural scenes.

2. Conclusion

Reading The Vision Revolution gave me the impressionthat a book format was inappropriate for the author's ideas.There was not enough material and the lack of citationsallowed too much uncritical conjecture. The developmentof Changizi's arguments and clarity of his logic could havebenefited from peer review and more demanding editing.Fortunately, he based the four chapters of the book on oneor two papers in each of the scant four chapters and sothese few ideas are readily available in formats that aremore concise.

I had hoped to recommend a book based on many positiveattributes. These might have included reports on innovativeresearch from groundbreaking recent studies or outlining anew paradigm for vision or evolution. To this end, I wouldrecommend to anyone interested in visual mechanisms orfunctional explanations of visual processes The EcologicalApproach to Visual Perception by Gibson (1986) and Visionby Marr (1982).

Although I cannot recommend the current book, doing sogoes strongly against what I had hoped to be able toencourage in potential Evolution and Human Behaviorreaders. Scientists in the evolution of human behavior oftenfocus our investigations on higher-order cognitive and socialmechanisms. Although such work has generated substantialfindings not otherwise predicted or explained, we cannotneglect those areas of research that form the foundation of

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human behavior. In order for us to truly embrace thecomprehensive explanatory power of evolution by naturalselection that we champion, our work must encompass allcomponents of behavior—certainly those of its foundation.This book, if nothing else, demonstrates that thesefoundational areas pose promising regions awaiting integra-tive evolution science.

Russell JacksonE-mail address: rjackson@csusm.edu

References

Gibson, J. J. (1986). The ecological approach to visual perception.Hillsdale, NJ: Lawrence Erlbaum Associates.

Marr, D. (1982). Vision. San Francisco, CA: W. H. Freeman and Company.