Department Of Psychology, P220 Biological Sciences Bldg.,
University Of Alberta T6G 2E1 Canada
E-mail: chrisw@ualberta.ca

The concept of negation has been described by those who have grappled with it as "curiously difficult" (Wilden, 1980) and "far from simple and transparent" (Horn, 1989). Negation has been alleged by some to play a fundamental role in the human ability to symbolize. In this paper the role of negation in the evolution and development of symbolization and language is considered in a neurobiological context. The argument has two sections.

In the first section, the problem of negation is defined and described, with emphasis on the well-defined stage at which the human ability to use negation diverges from the analogous abilities of our closest living primate relations.

In the second section, this functional divergence is attributed mainly to differences in cognitive functions whose initial adaptive utility was related to behavioral control. Much evidence suggests that those functions are dependent on the development of a specific region in the human prefrontal neocortex. This is of particular interest in light of the relation that has been proposed between negation and symbolization.

In this abstract, the contents of the two sections are briefly summarized.

It has been independently proposed many times (from Plato to Spencer Brown) that negation is best defined not as enantion (contrary) but as heteron (other): i.e. that negation is a positive assertion of the existence of a relevant difference. If we define a 'relevant difference' as one which requires an active choice, a framework for ranking the increasing complexity of six forms of natural language negation is apparent. The highest and most complex form of negation- propositional negation- is the only negational form which necessarily pre-assumes fully-developed language production and comprehension, and is therefore of the least interest for those interested in the evolution and development of those abilities. The prior five forms appear in human development in a sequence of increasing complexity.

The first three forms of negation are:

i.) Negation as rejection/ emphasis of rejection of external entities

ii.) Negation as a statement of refusal to stop or start action

iii.) Negation as an imperative

All these forms may be dismissed as variations of a simple 'forced choice'- i.e as requiring the negator to choose a desirable alternative over an alternative that is clearly less desirable. These forms of negation all have analogues in many non-human animals.

The fourth form of negation- failure negation, or negation of a self-generated or planned action- is only a small variation on the third form of negation (imperative negation), in which the negating agent rejected the actions of another, and is also closely related to the the first two forms of negation. However, the differences between the third and fourth form necessitate a number of extremely important changes in the way concept of negation is used. This fourth form of negation is the first form of negation that is elicited without external coercion. More importantly, it is the first form that allows its user to reject an entity that he has himself generated. It is therefore the first form of rejection that can (and, in the case of past or future action, must) operate on a non-existent entity. The use of negation as a comment on ones own unsuccessful or prohibited action is therefore an intermediary case between negation as rejection of a salient external object, message, or action, and negation as rejection of an wholly internal proposition.

Although failure negation marks the beginning of the gulf separating humans from other animals, it is not totally absent in non-human animals. For example, De Waal (1982) describes a chimpanzee who tried to 'erase' a fear grin while it was happening. Note that two reasons the chimp was able to negate this particular behavior is because it was long-lasting enough to be negated while it was happening, and because it was a facial behavior, which made it possible to use the hands to negate it. The negation by the hands of an on-going behavior may be contrasted to the failure negation of a human infant, who uses this form of negation after the negated behavior has occurred. The anecdotal nature of the evidence and the slightly different quality of the human infant’s and the chimpanzee’s negation shows the gulf that is appearing between man and his most intelligent primate relative. There is no consistent situation in which self-generated negation of their own actions is seen in non-human primates.

The fifth form of negation – 'scalar negation' – is the first form of negation, which must necessarily be detached: i.e. used against an absent entity. For this reason, it is also the first form of negation that requires a stated predicate. Scalar negation appears very early in normal human children’s language development, and also appears in human children raised without exposure to a formal language model. However, it has no indisputable analogue among other primates.

Since a recognized absence only exists in contrast to a recalled presence, scalar negation is necessarily dependent upon memory. However, an infant does not comment on every absence- only absences which make a difference. Therefore, this form of negation is more specifically dependent on memory that enables what is present to shift attention to a stimulus that is (relevantly) not present. When a child reacts to an absence, he is in effect reversing the significance of the stimuli which are present, because it is only in the context of those present stimuli that any absence can be noticed- what is absent doesn’t look like anything. In reacting to an absence, what was previously ground (irrelevant context, in virtue of not being the relevant absent entity) must now be interpreted as figure (relevant context, in virtue of pointing to the relevant absent entity).

The ability to make such internally-controlled shifts of significance has been well studied. There is strong consensus about the primate neurological substrate that underlies it. It is primarily reliant on two closely interconnected regions, the dorsolateral and orbital prefrontal cortex. The evidence implicating these areas comes from localized electrical stimulation, localized dopamine depletion studies, single cell recording studies, and brain imaging studies (see Diamond, 1988, 1991 & Deacon, 1997 for reviews). All these techniques suggest that the prefrontal cortex plays a specific role in choosing the appropriate behavior from a set of possibilities under conditions which require the subject to modulate his current behavior based on changing contexts, especially when those changes require the overcoming of an innate response tendency. Inasmuch as "Attentional development can be broadly characterized as a systematic increase in the child’s ability to override innate tendencies" (Kinsbourne, 1992, p. 261), these cortical regions may be characterized in general terms as controlling attentional shifting.

The appearance of displaced reference in scalar negation is a symptom rather than a cause of the ‘language insight’. The 'language insight' is the result of an incremental increase in the human infant's ability to make actions contingent upon internal markers. Most animals are limited to differentiating only those dimensions in the world that they are born ‘carrying’ or learned dimensions that have direct biological significance and are marked in the environment. Human beings are unique in our ability to construct and project onto the world an enormous number of abstract (displaced) dimensions of relevance. The 'cognitive clay' that we use to construct those dimensions is negation as heteron: our ability to formulate and follow rules about how to make the either/or distinctions that underlie the use of what is not present to shift attention.

Clearly many of the distinctions we make are made possible by language. The opposite relation holds true for some early forms of negation. Rather than being made possible by language, those forms of negation make language possible, in virtue of their role as necessary precursors to displaced symbolic reference. The fact that these abstract forms of negation have a specific behavioral utility suggests a plausible incremental adaptive pathway that could have spanned the 'adaptive gulf' separating the symbolic power of human language from the poor imitation of those powers that we find in other primates.

Acknowledgments: This paper was written while I was a research associate at the Center for Cognitive Studies at Tufts University. Thanks to Richard Griffin and Elena Nicoladis for valuable comments on earlier drafts.

 Conference site: http://www.infres.enst.fr/confs/evolang/