Saturday, 25 April 2009

Language & Species (1990), by Derek Bickerton

Derek Bickerton (b.1926) is professor emeritus of linguistics at the University of Hawaii and believes that creole languages provide a powerful insight into both the acquisition of language by infants and the origins of language in humans. A creole is a stable fully-functional language apparently arising from a pidgin, which is a stripped-down lingua franca arising when people sharing no common tongue have to live and/or work together. Examples include merchant seamen in distant ports and, historically, slaves in the West Indies.

Bickerton is the main proponent of the Language Bioprogram Hypothesis (LBH). This theory states that the structural similarity between many creole languages must arise from an innate capacity in the brain.

The following is a summary of Bickerton’s 1990 work Language and Species:

Chapter 1 The Continuity Paradox
Human and animal behaviour separated by one major distinction that not often appreciated – language. Animal communications are holistic and limited, e.g. vervet monkeys have warnings for various types of predators. By contrast, human communications are complex and unlimited. How did one evolve from the other? The theory of evolution states that features do not arise de novo but must be built incrementally upon something already in existence, but how can something infinite arise from something finite? This is known as the Continuity Paradox.

Bickerton resolves this paradox with the bold assertion that language in humans did not arise from the vocalizations of other animals and that its primary function is not in fact communication but representation. Communication is no more than a handy spinoff.

Nouns do not correspond to real objects, only representations of them. If this were not the case we could not have words for things like unicorns and golden mountains, which do not exist in the real world. Our view of the world is always representational and not absolute – what we see is a representation built up by sensory data; through a glass, darkly as St. Paul might have put it.

Chapter 2 Language as Representation: the Atlas
Language can be regarded as a means of mapping reality in a style analogous to both an atlas and an itinerary book. It important to realise that the atlas and the itinerary book are both representations of reality and that therefore they cannot represent with absolute verisimilitude. This limitation also applies to language – it does not directly map the experiential world. Language is a mediated mapping, a mapping that derives from the processing of sensory inputs.

In this chapter, Bickerton considers the atlas-like properties of language and states that a word can have three levels of meaning. Our knowledge of the world, in common with that of other animals, is derived from a series of mapping operations. The first of these – shared with other animals – is from existential objects to neural cells and networks in the brain. The first level of meaning is simple perception of, say, a leopard (non-italicised and not in quotes). We can only perceive a leopard when one is actually present, but we can think about leopards in their absence. This second level of meaning is the concept of something, for example “leopard” – the concept of leopards (in quotes). Some animal such as frogs almost certainly don’t have concepts. Frogs react quickly to snap up passing insects, but this is simply a hard-wired reaction to small rapidly moving objects (it ignores stationary insects and reacts to pellets flicked across their line of vision, but it works more often than not). Humans on the other hand do have concepts: for example an unidentified sound at night will be matched against possible explanations. Vervets probably fall somewhere in between and can equate the smell, sound and sight of a leopard with the same thing. Finally there is leopard (italicised), which refers to the word itself – a label - without any clear meaning being necessarily attached to it.

“Leopard” and leopard are defined in terms of (the perception of a) leopard, but this isn’t necessarily always the case; (the perception of a) burglar can only be expressed in terms of the concept of a “burglar” and the word burglar; we can define “paranoia” and label paranoia, but we cannot perceive paranoia.

Units relating to entities are insufficient to describe the world, because pretty well everything we see is doing something; for example walking, running, swimming, flying, etc. The subject/predicate distinction in language is so fundamental that it tends to be taken for granted, but it corresponds to nothing in nature. You cannot see an animal without perceiving at the same time what it is doing, e.g. a cow grazing. There is no word for cow-grazing, but we would expect there to be if language exactly mirrored reality. One possibility is that this is for reason of economy, because we’d need words for cow-running, cow-mooing, etc. But Bickerton believes that the explanation is that the concept of entities preceded the concept of behaviours. Behaviours are more abstract than entities; a cow cannot be anything other than a cow, but many types of animal can graze or run.

Behaviours are of course not the only things that can be predicated of entities. Properties such as size, colour, temperature, etc may also be attributed to entities. Typically these adjectives are paired, large/small, hot/cold, fast/slow, etc. While we can have words such as fast, faster and fastest, there is no language that represents a continuum of, say, speeds or temperatures.

The level of representation given by the lexicon abstracts away from and interprets the flux of experience. It derives a wide range of entities, together with behaviours and attributes that can be predicated of these entities. These form an inventory of everything that we see; however the lexicon is not unstructured.

Words are hierarchical e.g. animal -> mammal -> dog -> Spaniel. The word “anger” includes a range of words from irritation and annoyance through to rage and fury. Anger in turn falls in the category of emotion. Words can not only be converted to strings of other words, but fall into place within a universal filing system that permits any concept to be retrieved and comprehended.

Words are also constrained by contiguity. For example there is no word for “left leg and left arm”, or “every other Friday” or “red and green”. The referent must be an uninterrupted piece of matter or time or space. This even applies to abstract properties like ownership, location, possession, existence. Some languages, such as English, use one verb (is) for existence, location, ownership (e.g. there IS a book, the pub IS across the road, the book IS yours) and another (have) for possession (I have a book); but no language groups together existence/ownership and location/possession (the equivalent of the pub HAVE across the road). This suggests that contiguity constraints exist even in highly abstract domains. Semantic space may well be an intrinsic property of the brain; the lexicon is carved up into convenient chunks.

Chapter 3 Language as Representation: the Itineraries
While a map can tell you what the terrain is like, an itinerary is required to tell you what journeys may be taken. Similarly there are rules governing a journey through semantic space. Sentences are underlain by three types of structural consistency: predicability, grammaticisation and syntax.

Predicability imposes constraints between entities and predication – e.g. “the story is true” or “the cow is brown” are permissible, but not “the story is brown” or “the cow is true”. Only abstract qualities can be predicated of abstract nouns; and concrete qualities of concrete nouns. What can and cannot be predicated can be drawn up on a tree diagram. A quality at the top of the tree can be predicated of any class below it, but of no class above it. A quality on a side branch can only be predicated of a class on the branch below it.

For example, trees, pigs and men can all be dead; but only pigs and humans can be hungry; and only humans can be honest. All of these things plus thunderstorms can be nearby, but only thunderstorms could have happened yesterday; and so on.

Three observations may be made about the tree. Firstly it has binary branching. There is no obvious reason for this. Why only two? Why not three or more branches at each node? Secondly there is a contiguity constraint – for example anything applying to humans and plants must also apply to animals. Thirdly the tree does not seem to be derived from experience of the world as children as young as three or four used only slightly truncated trees. This does suggest that language as a classification mechanism is constrained by the human-specific conceptual analysis of the natural world.

Grammatical items are structural pieces that hold the meaningful parts of the sentence together – either inflections (-ing, -ed, etc), or words like “of” as in “the handle of the door”, or above, below, on, in, at, by, before, after, while, etc. Some languages to not express all these relations; others express relations not found in English. For example Hopi and Turkish both have inflections that differentiate between information gained through personal experience or obtained second hand. But grammaticization is only used on a few relations – those pertaining to singular/plural, and past/present/future (tense).

No language grammaticizes more than a fraction of the possible relations and while tenses and singular/plural seems to be a universal feature of language there is no language with grammatical constructs for edible/inedible, friendly/hostile, etc, even though these things would be useful. It seems that we are obliged to grammaticize some things, yet other things cannot be grammaticized. While one might dismiss this as a mere convention of languages, conventions can be broken and these never are. We can expand lexicon but not grammar. The latter appears to be a black box; we can neither alter it nor explain it.

Syntax is highly complex, yet we can all master its subtleties. A sentence is constructed of phrases; each phrase is a hierarchical not linear entity. A sentence of 10 words can be re-arranged over 3 million ways, only one of which is correct – yet we can do it effortlessly. Without syntax, complex ideas could not be communicated.

Chapter 4 The Origins of Representational Systems
Language must have evolved as a representational system, not for communications. How did this happen? Our senses give us a species-specific view of reality, only a subset of the data potentially available (e.g. little smell data, unlike dogs). This is the primary representation system, or PRS. All such systems arose from cells that could differentiate between two states, a distinction between sensory cells and motor cells, and motor cells capable of more than one behaviour type in response to a given stimulus. Humans alone have a secondary representation system (SRS) – language.

At lowest level there are organisms like sea anemones that can identify chemical signature of hostile starfish and execute an escape manoeuvre. Next is conditional response such as a crayfish that becomes habituated to being touches and eventually does not waste energy on an escape manoeuvre, or a grub that only moves if light-levels increase above a certain threshold. Ability to evaluate data is more complex in – say – lizard stalking a fly, where there is actual data processing by the brain leading to a choice of behaviours.

Vervet monkeys are genetically-programmed to respond to snakes. Similarly, if you touch something hot you move your hand away without thinking too hard. But such an approach has its limitations. Wildebeest do not always flee when they see a lion. If they did, they’d have less time to feed and they’d either exhaust themselves or starve. So they become alert – indeed they experience fear. But they don’t flee until threat assessment becomes critical. But fear – an emotion – is crucial to making a decision to flee.

Representations are either innate (metabolizing food, growing hair, producing sentences, etc) or learned (writing, sewing, swimming, etc). We are conscious of learned representations, but cannot access innate representations. But all representations lead to category formation – to form a category three things are needed: an object in the external world; patterns of cell activity in observers brain directly or indirectly triggered by the object’s presence; and the observer’s response, both internal and external to these patterns. Categories are species-specific.

For humans, categories are basically concepts, “concept” is simply the name we give a category. In non-human animals, categories might be referred to as proto-concept. Which came first – language or concepts? Probably language originally labelled proto-concepts derived from pre-linguistic experience; this was later expanded to be capable of deriving concepts not present in PRS, e.g. absence, golden mountains, etc. While the SRS can divide the universe exhaustively, PRS must do the same, e.g. for frogs, everything is either a frog, a pond, a large looming object or something else not relevant to frogs.

Pigeons can develop quite sophisticated categories – can be trained to peck certain classes of object, e.g. tree pictures. Such behaviour cannot be entirely innate as they can be trained to respond to objects they could have no knowledge of. But some categories - trees, humans, etc – probably are innate; probably categories of things that are significant to a particular species are innate, but the ability to analyse novel objects as well, by utilizing this processing power subsequently evolved. However provided the referents of particular proto-concepts remained relevant, these would be retained and new ones would be added over evolutionary time.

Categories/proto-concepts such as “tree”, “human” etc may be precursors of nouns. Some monkeys have temporal cortex cells that respond to movement of a primate-like figure – could these be proto-verbs? But these are agent-plus-actions rather than actions – human language does not conflate an entity and its behaviour into single words; subject-predicate distinction is fundamental as seen earlier.

Tiger running, tiger walking, tiger attacking could be broken down into “tiger” + action; however tiger running, dog running, insect running cannot so easily be broken down into X + “running” as the types of “running” differ, as opposed to only one type of tiger. This is why verbs are more abstract than nouns and are harder to represent. However if only a subset of a particular behaviour is considered, it can be restricted to species likely to perform it – for example only primates can “grab with hand”.

Proto-nouns might have represented species interacting with hominids. Proto-verbs might have been actions only hominids could perform. This implies awareness of conspecifics with which the creature interacts – in turn implying a social species. Awareness of self is a cornerstone of language and consciousness.

Chapter 5 The Fossils of Language
Ape language is basically very limited. Does it represent an earlier form of human language? It is comparable to that of a 2-yr old human. Bickerton then considers the possibility that “ontogeny recapitulates phylogeny”. “Genie” was a 13 year old girl imprisoned from birth and not exposed to language. After her rescue, she learned only ape/2 yr old-type language and could not be taught full language. Genie failed to acquire human language but has acquired something else. Language therefore cannot be a unitary system requiring input during critical period or Genie would have not acquired any language at all. Genie acquired proto-language (a robust “mature technology”) but could not go further and acquire full language. The means of acquisition are not the same for both.

Pidgins are proto-languages. Numerous examples known, for example slaves in West Indies, immigrants to Hawaii from 1880-1930, Russian and Scandinavian sailors; their speakers nevertheless have normal linguistic skills.

Thus there are four classes of proto-language speakers: apes, under-2-yr-olds, adults deprived of language and pidgin-speakers. 1. Language has word order constrained by general rules, formal structure; proto-language does not. 2. Language uses null elements in a consistent manner; proto-language does not (not well explained). 3. In language verbs have one, two or three arguments (like subprograms). Sleep 1 “Fred sleeps” Go 2 “Fred goes to bed” Give 3 “Fred gives Bert five pounds”. 4. Proto-language cannot expand phrases – the man to the tall man, tall bald man, tall bald fat man etc, or concatenate phrases – John wants books -> John wants books to study. 5. Proto-languages do not inflect.

Proto-language is not a blanket term for ungrammatical language (e.g. people with aphasia due to damaged Broca’s area). It does appear to be a distinct thing in itself. But how did we get from proto-language to full language?

Chapter 6 The World of Protolanguage
Relative brain size jumps at the Homo habilis-ergaster/erectus boundary. H. habilis is claimed to show enlarged Broca’s and Wernicke’s areas and was right-handed; first signs of lateralization. Proto-language could have begun with H. habilis (Bickerton’s hominid evolution diagrams represent the state of knowledge current in 1990). Tools and language are unlikely to have co-evolved. If H. habilis had proto-language than H. ergaster/erectus possibly had language – in which case why did the Acheulian tool tradition not evolve? It is likely that H. habilis did not have language and H. ergaster/erectus had only proto-language. Possibly this aided them in the use of fire, which seems well-attested. Bickerton rejects the theory of “gesture language”. If this was correct, infants would use sign-language (assuming ontogeny recapitulates phylogeny); language must have been vocal from the beginning. Sufficient cortical control was probably achieved by the time of Australopithecus afarensis – involuntary calling would have been maladaptive to a species that operated on the savannahs of east Africa. Vocal tract developed as the larynx lowered, increasing the risk of choking. Proto-language probably didn’t require the perfected human vocal tract, which would have been maladaptive if it had developed first. However changes to the vocal tract would have been favoured after proto-language developed. Original vocabulary was probably small – phonology may have developed in conjunction with syntax. A pre-phonological stage may exist in pre-syntactic children.

Reliance on sight in primates increased area of brain needed to process data: increased PRS categories -> drove things on in the direction of language. Chimps have few enemies but savannah-dwelling hominids have many. Curiosity about surroundings; recognising and categorizing was adaptive and selected for.

Few animals face the same set of problems as early humans as few are both social and omnivorous, with such varied feeding habits. Social herbivores move in herds, social carnivores hunt in packs and kill much larger animals; humans could not do this 2 million years ago. A band of foraging humans could split into small groups able to use proto-language could get the attention of others and lead them to finds too large for them alone.

There are three types of learning: Experiential learning (e.g. I am trying to escape from a tiger, I jump into a river and swim across and the tiger fails to follow. Next time I am chased by a tiger I’ll head for the river); Observational learning (I see a man escape from a tiger by swimming across a river and conclude this is the thing to do if I’m in the same position); and finally Constructive learning (I note that tigers will go round a body of water rather than swim across it. I conclude that tigers avoid water and if attacked by one this might offer an escape route).

Pretty well all animals are capable of learning from experience, and many can learn by observation such as the blue tits that began pecking their way into milk bottles in the UK in the 1970s. The majority of these birds undoubtedly learned the trick from watching their conspecifics.

But is any animal lacking language capable of constructive learning? For apes, it appears to be possible only in a limited fashion and all the elements involved need to be physically present. Anything involving absent individuals or classes of entity requires a form of representation beyond those available to non-humans.

There is nothing in the fossil record to suggest that H. ergaster/erectus had cognitive capabilities comparable to ours. It therefore seems likely that H. ergaster/erectus lacked syntax, hence had only proto-language and could not think as we do.

Chapter 7 From Protolanguage to Language
Proto-language can evolve to true language without an intermediate. There is no plausible intermediate between the two. A child moves rapidly from proto-language to full language, falling back on the former only when their lexicon does not have the necessary grammatical words. Pidgins develop into creoles – i.e. a true language arises from a proto-language. Creoles tend to have the same grammar regardless of the constituent languages suggesting a biological basis for it. In neither of these proto-to-full language transitions is an intermediate involved.

Modern human behaviour (whenever this did emerge) was probably linked to emergence of true language. Bickerton seems to support early emergence (i.e. AMH were behaviourally modern from Day 1) contra Klein (1999 etc), Mithen (1996), etc. The gap in the fossil record he attributes either to use of perishable materials while H. sapiens remained confined to Africa, or that it took time to develop the artefacts of modern humans despite always having the capacity to do so. This view, quite radical for 1990, is basically the position taken by McBrearty and Brooks (2000).

Cases for an intermediate language are not plausible because the intermediate would be as complex as the full-blown language. Nor could features of a true language be acquired piecemeal as they are all too interlinked. The only way a gradual process could have happened would have been if the structural principles were at hand, but the lexicon was still limited.

Proto-language probably acquired grammatical items – negator, wh-questions; auxiliaries (can, must, etc); time – earlier/later; location particles (often only one meaning on/in/at/to/from); possibly even pronouns.

The verb arguments are of three types (thematic roles) Agent, Patient, Goal – e.g. Bert (agent) gave five pounds (Patient) to Fred (Goal). These roles are not given by nature but are high-level abstractions. They probably originated through millennia of day-to-day hominid routine, with Agent as the most important. These roles were probably not systematically expressed.

These two developments in proto-language could have facilitated the emergence of true language. Verbally expressing emotion may have come next, followed by use of proto-language to model internal states of others. But how did we get to language? Could one mutation have done it? Could one mutation have generated a) syntax, b) skull features and dimensions and c) the larynx positioning?

Author believes possible explanation for a) is visual-processing areas of the brain could have been pressed into service to process syntax and not some central repository such as Broca’s area. This would explain why aphasia affects only grammaticization, not syntax (allegedly) [the role of the FOXP2 gene wasn’t discovered until 1998].

Chapter 8 Mind Consciousness and Knowledge
Einstein’s claims notwithstanding, language is required for thinking. Much goes on beneath the level of conscious thought that the thinker is unaware of. Mind, consciousness and the search for knowledge may all arise from having a language-based SRS with a syntax processor.

Even if the human mind does derive from language, this does not tell us about the precise relationship between language and mind. It was once believed that a full understanding of language would serve as a “window on the mind”, but this implied that language permeated the mind at every level. This in turn implied that the mind was a single problem-solving mechanism, as often been assumed by empiricists.

This view is seemingly at odds with the “modular mind” theory of Jerry Fodor, Howard Gardner, Annette Karmiloff-Smith etc. Despite the success of modularity theories, there is a problem. If modularity emerged after language there would not have been enough time for other modules, each with their own unique mechanism, to have evolved subsequently. [If Steven Mithen is correct, modularity considerably predates the emergence of fully-modern Homo sapiens (Mithen, 1996)].

Conversely if modularity emerged first and remained largely uninfluenced by the development of language it would only work if these were independent of language [which I believe is the accepted view] and language was not a representational system but merely a code for expressing the output [why?]. It would also predict human intellectual capabilities largely pre-existed language, which is clearly not the case [Mithen’s “cognitive fluidity” seems to be the answer here (Mithen, 1996)].

Bickerton’s resolution of this modularity versus window-on-the-mind problem is to suppose that that syntax processing is not an isolated module but a particular type of nervous organization that permeates and interconnects those areas of the brain devoted to higher reasoning processes, concepts and the lexicon, a type of organization that automatically sorts material into binary-branching tree structures. Other modules will then receive and output material that has been pre-processed to conform to syntactic principles [this suggests a mechanism by which Mithen’s “cognitive fluidity” might work, though in fact Mithen is critical of Bickerton’s proto-language and believes utterances of early humans were holistic (Mithen, 2005)].

What is “I”? Am I the whole body or just mind or a homunculus? Human language divides entity from behaviour, so “I am hungry” suggests “I” is divided from being hungry. Is the central directing “homunculus” a product of language – nothing more than an illusion – or is it something more? The latter suggests the human organism is indeed divided in some way, and not necessarily the way language suggests it is. In other words, the brain is modular.

Experiments with left/right hemispheres have suggested that right hemisphere has only PRS, lacks syntax capability but can do inference.

“I” cannot control the entire organism – cannot control bodily functions, which carry on if I’m asleep or unconscious. There is accessible I – linked to language and inaccessible I – not linked to language. This is better than mind-body model. Talking I is a module that forms a part of accessible I, though sometimes other modules grab the microphone. “I forced myself to do x” means “information in the SRS indicated that doing X would bring long term benefit, despite short-term appeal of doing Y”.

Chapter 9 The Nature of the Species
We are living in the fourth age of man [taken to be H. sapiens only]. In the first phase, from 200K years ago to 40K years ago, humans were hunter-gatherers confined to Africa. In the second phase, humans left Africa and “beat the Neanderthals”. The third phase, which began with the coming of agriculture at the end of the last ice age, introduced territorialism and inequality. [In fact early Neolithic societies, such as that at Catal Hoyuk in Anatolia, seem to have been fairly egalitarian, though there is no doubt that sedentism, which made it possible to accumulate possessions for the first time, led to the beginnings of social inequality. The notion that pre-agricultural man was not territorial seems highly dubious to me, considering that chimps are territorial.]

The Fourth Age begun 400 years ago, when inequality between state-level societies emerged.

“Did Syntax Trigger the Human Revolution” (Bickerton, 2007) is a paper submitted as Bickerton’s contribution to a series of papers published after the 2005 Cambridge conference entitled “Rethinking the Human Revolution”, part of the on-going debate about the mode, tempo and timing of the emergence of modern human behaviour.

Bickerton rejects the notion of a “Great Leap forward” 50-30 kya in Europe; the evidence now suggests that features thought to be novel to Europe emerged in Africa earlier. Did characteristically human cognitive capacities (CCHC) emerge gradually over 200-300 ky? It is more plausible that the change occurred with emergence of our own species. Bickerton considers and rejects the notion of studying tool sophistication because of the difficulty of agreeing what constitutes sophistication. There are also the assumptions that gradual increase in tool complexity implies increase in CHCC and that the moment a CHCC emerges it must result in artefact change. It is more plausible that when modern humans evolved, CHCCs emerged with them, but the novel artefacts only appeared later in response to selective pressure or cultural development. However it is equally implausible that these new CHCCs lay dormant for extended periods of time. An in between position seems the most likely.

It is possible to assume that the Acheulian hand-axes required the maker to conceptualise the finished article [the accepted position] but makers could simply copy and possibly modify and improve upon existing axes. Bickerton believes second possibility is more parsimonious, as there are objects intermediate between Oldowan and Acheulian, and between Acheulian and subsequent industries. On this picture, all human (inc. pre-sapiens) artefacts fall into two classes – those that are modifications of earlier artefacts and those that are completely new and would have to be imagined first (e.g. fish hooks, “Venus” figurines, etc).

What is required to create novel artefacts? Not necessarily bigger [or even more encephalised?] brains. Bickerton returns to his thesis of a proto-language developing around 2 mya. It is not, by itself, enough to produce novelties, though it would have increased social and foraging capacities. To sustain the trains of thought needed to produce novelties, something else is required. Bickerton distinguishes between “thought 1” (pre-linguistic thinking), “thought 2” (thinking with proto-language) and “thought 3” (thinking with full language). Only “thought 3” would permit a sustained train of thought.

Thought 1 could permit such thoughts as “that is a lion” (reacting to the sight of a lion) or “I am hungry” (feeling peckish) but not “hungry lions are dangerous” which would require the ability to instantiate the abstract class of “lion” at will rather than in response to actually seeing a lion. Australopithecines and present-day apes were/are probably restricted to thought 1.

Proto-language could have been holistic, like Steven Mithen’s “hmmmm” (Mithen, 2006) or – as per Bickerton’s position – comprise short, unstructured strings of single units (either oral or gestures) roughly corresponding to the individual words of present-day languages. Such a proto-language would have had a term for a lion corresponding to the abstract class “lion”. It would have enabled its possessors to think about things in their absence without triggering the responses (fight, flight, wait, etc) that a pre-linguistic signal might have occasioned.

Bickerton dismisses the long-running debate on the possibility of thought without language. If thought is mental computation, then anything with a brain is capable of thought. The issue is how to think at a level that creates novel behaviours or artefacts. Thinking is not conducted by words or images, as the brain does contain words and images, only neural pathways. Proto-language units enable creation of neural representations that allow thinking without direct reference to external objects to take place. These units could have been used for both language and thought. The former would have required an additional layer of mapping to a phonological representation for utterance and also a relationship between units – words and/or signs.

Language and proto-language both concatenate units of which they are composed, but language does so in a highly-structured manner with embedded phrases and clauses where as proto-language simply assembles words like beads on a string. Complex thought would have been impossible and proto-language speakers would have remained confined to thought 2.

The crucial difference is syntax. Bickerton believes that the same mechanism required to produce full language also enables the brain to marshal the complex trains of thought needed for innovation. Since the functionality is similar it is more parsimonious to assume the existence of just one rather than two distinct mechanisms. Bickerton speculates the need for more complex utterances might have led to the evolution of a syntax system, which served without further modification as an organizer of thought, and that its possessors are capable of thought 3. It is therefore likely that the development of syntax of language was a necessary and possibly sufficient pre-requisite for the emergence of modern human behaviour.

Bickerton D (1990): “Language and Species”, University of Chicago Press, USA.

Bickerton D (2007): “Did Syntax Trigger the Human Revolution?” in Rethinking the human revolution, McDonald Institute Monographs, University of Cambridge.

Fodor J (1983): “The Modularity of Mind”, MIT Press, Cambridge, MA.

Gardiner H (1983): “Frames of Mind”, Basic Books.

Gardiner H (1999): “Intelligence Reframed”, Basic Books.

Karmiloff-Smith A (1992): “Beyond Modularity”, MIT Press, Cambridge, MA.

Klein, R. (1999): “The Human Career” (2nd Edition), University of Chicago Press.

Mithen S (1996): “The Prehistory of the Mind”, Thames & Hudson.

Mithen S (2005): “The Singing Neanderthal”, Weidenfeld & Nicholson.

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