Update TRENDS in Cognitive Sciences Vol.8 No.6 June 2004 247 negativity for long-distance dependencies [25].Usinga normal and pseudo-word sentences of different processing demands: a complex artificial grammar containing different types functionalmagneticresonanceimagingstudy.Neuroimage 15, 1003–1014 11 Ben-Shachar, M. et al. (2003) The neural reality of syntactic of phrase structure similar to natural languages, but (unlike transformations: evidence from fMRI. Psychol. Sci. 14, 433–440 natural languages) not including recursion, it was demon- 12 Kuperberg, G.R. et al. (2000) Common and distinct neural substrates strated that violations elicited an early anterior negativity for pragmatic, semantic, and syntactic processing of spoken sentences: followed by a P600 [26]. These data suggest that the brain an fMRI study. J. Cogn. Neurosci. 12, 321–341 response to violations is determined by the type of structure 13 Meyer, M. et al. (2000) Neurocognition of auditory sentence compre- hension: event-related fMRI reveals sensitivity to syntactic violations used, rather than the artificiality of the language. and task demands. Brain Res. Cogn. Brain Res. 9, 19–33 14 Moro, A. et al. (2001) Syntax and the brain: Disentangling grammar by Conclusion selective anomalies. Neuroimage 13, 110–118 In summary, the research reported by Fitch and Hauser [3] 15 Friederici, A.D. et al. (2003) The role of left inferior frontal and provides intriguing evidence for the notion that the ability to superior temporal cortex in sentence comprehension: localizing processPSGandtherebyhierarchical structuresisuniqueto syntactic and semantic processes. Cereb. Cortex 13, 170–177 humans. This claim receives support from studies in the 16 Newman, S.D. et al. (2003) Differential effects of syntactic and semantic processing on the subregions of Broca’s area. Brain Res. neuroscience of language in humans, which reveal particu- Cogn. Brain Res. 16, 297–307 lar clusters of brain activation dependent on the type of 17 Fiebach, C.J. et al. Distinct neural correlates of legal and illegal word structural information processed. Broca’s area (BA 44/45) is order variations in German: how can fMRI inform cognitive models of most obviously activated during language processing when sentence processing? In The On-Line Study of Sentence Comprehension long-distance dependencies and transformational struc- (Carreiras, M. and Cifton, C., eds), Psychology Press (in press) 18 Musso, M. et al. (2003) Broca’s area and the language instinct. Nat. tures (i.e. hierarchical structures) are processed. Neurosci. 6, 774–781 19 Opitz, B. and Friederici, A.D. (2003) Interactions of the hippocampal References system and the prefrontal cortex in learning language-like rules. 1 Lai, C.S.L. et al. (2001) A forkhead-domain gene is mutated in a severe Neuroimage 19, 1730–1737 speech and language disorder. Nature 413, 519–523 20 Tettamanti, M. et al. (2002) Neural correlates for the acquisition of 2 Enard, W. et al. (2002) Molecular evolution of FOXP2, a gene involved natural language syntax. Neuroimage 17, 700–709 in speech and language. Nature 418, 869–872 21 Fletcher, P. et al. (1999) Learning-related neuronal responsesin prefrontal 3 Fitch, W.T. and Hauser, M.D. (2004) Computational constraints on cortex studied with functional neuroimaging. Cereb. Cortex 9, 168–178 syntactic processing in a nonhuman primate. Science 303, 377–380 22 Seger, C.A. et al. (2000) Neural activity differs between explicit and 4 Hauser, M.D. et al. (2002) The faculty of language: what is it, who has implicit learning of artificial grammar strings: an fMRI study. it, and how did it evolve? Science 298, 1569–1579 Psychobiology 28, 283–292 5 Sanides, F., ed. (1962) Die Architektonik des menschlichen Stirnhirns, 23 Strange, B.A. et al. (2001) Anterior prefontal cortex mediates rule Springer learning in humans. Cereb. Cortex 11, 1040–1046 6 Embick, D. et al. (2000) A syntactic specialization for Broca’s area. 24 Baldwin, K.B. and Kutas, M. (1997) An ERP analysis of implicit Proc. Natl. Acad. Sci. U. S. A. 97, 6150–6154 structured sequence learning. Psychophysiology 34, 74–86 7 Stromswold, K. et al. (1996) Localization of syntactic comprehension by 25 Friederici, A.D. (2002) Towards a neural basis of auditory sentence positron emission tomography. Brain Lang. 52, 452–473 processing. Trends Cogn. Sci. 6, 78–84 8 Caplan, D. (2001) Functional neuroimaging studies of syntactic 26 Friederici, A.D. et al. (2002) Brain signatures of artificial language processing. J. Psycholinguist. Res. 30, 297–320 processing: evidence challenging the ‘critical period’ hypothesis. Proc. 9 Fiebach, C.J. (2001) Working Memory and Syntax During Sentence Natl. Acad. Sci. U. S. A. 99, 529–534 Processing, MPI Series of Cognitive Neuroscience, No. 23, Sa¨chsisches

Digitaldruck Zentrum, Dresden 1364-6613/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. 10 Ro¨der, B. et al. (2002) Brain activation modulated by the comprehension of doi:10.1016/j.tics.2004.04.013

|Book Reviews Is there only one way to become sapiens? How Homo became sapiens: on the evolution of thinking by Peter Ga¨ rdenfors. Oxford University Press 2003. £25.00 (250 pp.) ISBN 0 198 52850 7

Josep Call

Max Planck Institute for Evolutionary Anthropology, Leipzig, Germany

The evolution of cognition is an area that reasoning of Ga¨rdenfors as he revises a draft of his has received much attention in recent manuscript. years. Ga¨rdenfors has written a thought- This book combines insights from animal behavior, provoking and easy-to-read book on the archaeology, psychology, philosophy and neuroscience – evolution of human cognition. The book all in the quest for the understanding of the evolution of is presented as a dialogue between an human thinking. I particularly enjoyed the discussion on imaginary monkey called Egon that is the interplay of sensation, perception and imagination. eager to point out, often with a dose of Ga¨rdenfors provides a vivid account of how cognition sarcasm, potential loopholes in the creates ‘reality’ out of the internal and external inputs. His discussion about the role of simulation and integration Corresponding author: Josep Call ([email protected]). from various sensory inputs was extremely insightful. www.sciencedirect.com 248 Update TRENDS in Cognitive Sciences Vol.8 No.6 June 2004

Similarly, the discussion of the various types of mental Considering cognitive evolution as a function of both representation that constitute the inner world of humans common descent and convergence are important. A focus and other animals was very useful. Ga¨rdenfors’ ability to too narrow will provide only partial answers at best, and dissect the various components of cognition can also be erroneous ones at worst. seen in his treatment of areas such as theory of mind and language. Interpretation of narrow data sets Despite these and other strengths of the book, there was Related to the previous point, an exclusive focus on one thing that kept nagging at me while I read it. Although common descent invariably produces important oversights this book takes a comparative and evolutionary stance to of the data available. For instance, the author states that the problem of human thought, which is a welcome change chimpanzees are the only animals that fashion and use compared with much of the philosophical, psychological tools (p. 77) or that animals cannot keep track of time or and cognitive neuroscience work done today, it still does have episodic memories (p. 71). Quite to the contrary, there not go far enough in my view. The main problem is that are several bird species that also make and use tools [2,3] Ga¨rdenfors’ thesis on the evolution of human thought is and scrub jays have been shown to be able to keep track grounded on the idea of a scale naturae [1] and not a of time and have an episodic-like memory [4]. More Darwinian tree. It sees evolution as a linear progression importantly, an exclusive focus on common descent tends with some species at the top and others below that have to generate oversimplifications of the significance of the reached only certain degrees of cognitive complexity. This data for other species because when distantly related is an idea that has deep roots in Western thinking and that animals do something that not even we or our closest has exerted a powerful influence on the study of animal relatives do, it threatens to turn the scale upside down. For behavior and cognition [1]. instance, if the ability to use sonar to detect objects under One might speculate that the human psyche finds water were considered the pinnacle of cognition, dolphins, ladder-like structures irresistible, perhaps because they not primates, would be at the top of the ranking of complex are a reflection of our own human social systems. This cognition. In those cases it is easy to succumb to the influence is so strong that even though the author temptation to dismiss such evidence as unimportant. recognizes that there are no ‘higher’ and ‘lower’ animals One widespread way of doing just that is to invoke the (p. 13), thus distancing himself from the notion of a scale, notion of instinct. Indeed, instinct, like trial-and-error he still cannot resist this idea throughout the book. My learning, is one of the favorite tools that skeptics use to guess is that Egon would be glad to point out that turn the Darwinian tree into the Aristotelian scale. Such Ga¨rdenfors is no more able to avoid this problem than practice is so widespread that Donald Griffin criticized it in Boysen’s chimpanzees are able to avoid choosing the larger several of his writings [5]. Here, Ga¨rdenfors invokes of two quantities of food – a vivid reminder that all species instinct to dismiss or explain things as varied as chim- including humans are subject to their own biases. This panzee and other animal vocalizations (p. 99), chimpan- ladder-like stance does determine in great measure how zees’ reactions to leopards (p. 76), or hoarding in various the book flows and its scope, which is, in my opinion, too animals (p. 74). It might in the end turn out that some of narrow. Below I discuss three issues in which this is these skills have little flexibility, but the important point is particularly noticeable. that only research can tell. Using the catch-all term ‘instinct’ to explain these skills without proper research is Common descent and convergent evolution not very fruitful. In fact, one of the reasons why the From a comparative perspective, this is an ‘ape-centric’ concept of instinct fell into disuse was the repeated book, as most comparative data presented is based on tendency to invoke it to account for phenomena when no chimpanzee studies. This is perhaps because of the other clear explanation existed. misconception that only our closest relatives, in particular the chimpanzee, can inform us about human cognitive Progressive increment of cognitive capacities evolution. There is no question that focusing on our closest A basic theme of this book is that there are progressive relatives provides us with very valuable information for increments in cognitive capacities that culminate in the solving the puzzle of human cognitive evolution – and it is appearance of free will and language in humans. Although important that Ga¨rdenfors has turned to chimpanzees in the idea of a progressive increment of cognitive abilities this quest. However, this is not the only source. It is makes perfect sense from a scala naturae point of view, it is equally important to look at distantly related species to more problematic when viewed from an evolutionary gain insights about the way cognitive systems evolved viewpoint. Although it can be said that, in general, when faced with particular selective pressures. One can organisms have increased in complexity from unicellular see that hoarding or alarm calling have evolved in various to multicellular organisms and from simple to complex animal taxa independently and have produced similar nervous systems, taking this increase-in-complexity argu- convergent solutions. This creates a situation that some ment at face value can be misleading. There have been might see as paradoxical because two distantly related decreases in complexity throughout evolutionary time. For species facing similar pressures may be closer in their instance, parasites have often lost many of their body cognitive skills than species that are closely related but regulatory functions because they are performed for them have faced different pressures. It is often assumed that by their hosts. Similarly, animals such as moles living closely related species will always be close in their exclusively underground have considerably reduced capa- cognitive mechanisms, but this is not necessarily true. bilities of their visual system. Examples in cognition are www.sciencedirect.com Update TRENDS in Cognitive Sciences Vol.8 No.6 June 2004 249 also available. Dogs present a 20% reduction in brain size expecting that those functions, once they are properly compared with wolves with an equal head size [6]. There is investigated in other species, will be identical to those even some evidence suggesting that dogs may have ‘lost’ found in humans in every detail. some problem-solving abilities in comparison with wolves, Humans are by definition unique, just like any other although they may have gained some communicative species on the planet. Thus, whether other animals think abilities with humans [7]. Note that dogs and wolves like us is not, in my view, a very interesting question. A shared an ancestor relatively recently – approximately better question is how other animals think. It is only when 100 000 years ago [8]. we abandon the idea of a scale with humans at the top and So when it comes to a progressive increment of capaci- begin to learn more about the diversity of cognitive ties one has to be cautious and take into consideration systems in nature that we will begin to better understand selective pressures that have operated on each species over how humans (and some other animals) became sapiens. evolutionary time. For instance, neocortex in mammals has been associated with social intelligence and frontal References cortex is thought to be ‘the seat of higher cognitive 1 Hodos, W. y. Campbell, C.B.G. (1969) Scala naturae: why there is no functions’ (p. 25). However, birds also show social complex- theory in comparative psychology. Psychol. Rev. 76, 337–350 ity and complex cognition without a cortex. This illustrates 2 Hunt, G.R. (1996) Manufacture and use of hook-tools by New that there is more than one path to complex cognition – Caledonian crows. Nature 379, 249–251 3 Chappell, J. and Kacelnik, A. (2002) Tool selectivity in a non-primate, and humans do not have the patent on all of them. the New Caledonian crow (Corvus moneduloides). Anim. Cogn. 5, 71–78 In conclusion, this is a highly stimulating book that, in 4 Clayton, N.S. et al. (2003) Can animals recall the past and plan for the my opinion, could have been even better if the author had future? Nat. Rev. 4, 685–691 taken a broader comparative and evolutionary perspec- 5 Griffin, D.R. (1985) The cognitive dimensions of animal communication. tive. In the end, we are left with the impression that self- In Experimental Behavioral Ecology and Sociobiology (Hoelldobler, B. consciousness, seeking hidden causes, planning for the and Lindauer, M., eds), pp. 471–482, Sinauer 6 Coppinger, R. and Schneider, R. (1995) Evolution of working dogs. In future, time-awareness and free will are uniquely human The Domestic Dog: Its Evolution, Behaviour, and Interactions with skills. However, we should acknowledge that in reality we People (Serpell, J., ed.), pp. 21–47, Cambridge University Press do not know whether this is the case because these topics 7 Miklosi, A. et al. (2003) A simple reason for a big difference: wolves do have not received much comparative research attention not look back at humans, but dogs do. Curr. Biol. 13, 763–766 yet. It is acceptable to presume human uniqueness in these 8 Vila`,C.et al. (1997) Multiple and ancient origins of the domestic dog. cognitive functions as a working hypothesis from which to Science 276, 1687–1689 test other species, but we should be ready to change our theories if and when new evidence proves them inaccurate. 1364-6613/$ - see front matter q 2004 Elsevier Ltd. All rights reserved. More importantly, we should also not fall into the trap of doi:10.1016/j.tics.2004.04.008

Virtually losing your self Transcranial Magnetic Stimulation: A Neurochronometrics of Mind by Vincent Walsh and Alvaro Pascual-Leone, MIT Press, 2003. $55.00/£35.95 (304 pages) ISBN 0 262 23228 6

Julian Paul Keenan

Montclair State University, Department of Psychology, Dickson 225, Upper Montclair, NJ, 07043, USA

Recently, Decety and Sommerville [1] Asperger syndrome [5] lend credence to this argument. concluded that self–other separation is Convincingly, patients with asomatognosia [6], anosogno- modulated in part via neural mechan- sia [7], mirror-sign [8], TOM deficits [9], and generalized isms in parietal and frontal cortices of self-disregulation [10] all have predominately right hemi- the right hemisphere. This conclusion sphere damage. was drawn primarily from neuroimag- To further understand the relationship between self- ing studies, in particular, fMRI investi- awareness and the brain, a number of researchers have gations from their own laboratory as turned to Transcranial Magnetic Stimulation (TMS), a well as others, myself included. Further data from a realatively recent method of investigation. TMS theoreti- variety of sources including other neuroimaging tech- cally allows for the brief disruption of a given brain area. niques such as PET, ERP, and SPECT support the By applying a single pulse of TMS to a particular brain conclusion that right-hemisphere frontal and parietal region in a healthy subject, one is capable of inducing a regions are dominant for self-processing (for a review, ‘virtual lesion’ to the ‘virtual patient’. Therefore, admin- see [2]). Also, behavioral data in normals [3], split-brain istering TMS to a ‘self area’ should result in the disruption patients [4] and research in clinical populations such as ofperformancerelated toself-awareness. That is,if thebrain region(s) associated with the self are temporarily compro- Corresponding author: Julian Paul Keenan ([email protected]). mised (a virtual lesion), one should observe self-deficits www.sciencedirect.com