The Exographic Revolution : Neuropsychological Sequelae Chapter 7 The Exographic Revolution : Neuropsychological Sequelae

example, writing, or driving; (2) conditioned emotional responses, for example, a state of anxiety triggered by the sight of a rival; (3) perceptual learning, for example, learning how to distinguish various subtypes of a certain class, say, flowers or faces; (4) semantic memo­ ries, which tend to be abstract generalities encoded in language; and (5) episodic memories of personal experiences, which are highly specific, detailed and vivid. These five categories have been established for some time in experimental research, and, although there are still controversies about their neuro-chemical foundation, these are very likely to stand as functionally distinct subsystems from a cognitive standpoint. Neuropsychological studies of memory disorders, or amnesias, have shown that these different memory systems can break down independently of one another; for example, it is common to lose episodic, but not semantic memory, in amnesia (Tulving 1985). There is also evidence from brain-imaging research and clinical case studies that these types of memory depend on anatomically distinct brain networks. In addition, they have different storage and retrieval characteristics; for example, new skills are learned gradually through repetition and practice, whereas vivid episodic memories are usually acquired in a single trial. Some of these memory systems — most notably semantic memories — are special to humans, while others are shared with many other species (Tulving 1985). At a minimum, we must conclude that there are several kinds of engrams, which are learned and stored in various neural subsystems. Memory records stored outside the nervous system (for example, clay tablets, papyri, printed books, government archives or electronic data banks) can be called ‘exograms’ (Donald 1991; 1998). Exograms take many forms (Table 7.1). From present archaeological evidence, simple exograms were invented by biologically modern humans in the late Upper Palaeolithic. They took the form of significant objects that had been pierced, carved or painted. Over a very long period of time, and after Objects, manufactured or not, are ubiquitous in human cultural life and play an important role in our mental lives. Biologically modern humans have always been surrounded by meaningful objects, which can point, remind, entrench, signify and sustain the patterns of social custom and thought. They, and material culture in the wider sense, frame the ideas and routines that drive everyday life. They can be said to have cognitive ‘lives’ inasmuch as they enter into mind, solidify and channel shared experience and define the social order. But, to a degree, objects can also signify things to apes, monkeys, dogs, bears and cats. Objects remind them of past events, point toward certain patterns of action, entrench habits and define routines. Put into traditional terminology, objects are transformed into conditioned stimuli through association, and, in this behaviouristic guise, their cognitive role does not stand out as uniquely human. However, there is a way in which certain manufactured objects serve the human species in a unique, and evolutionarily novel, manner. I am referring to a class of manufactured objects that are sometimes called ‘symbolic technologies’. These are specifically designed to represent, communicate and store knowledge. Such objects introduce a completely new element into human cognition: external, that is, nonbiological, memory storage (as in an encyclopaedia, for example). Non-biological memory media enable us to record and display complex ideas in highly accessible formats that are easy to revise and refine. The introduction of radically new memory media into the cognitive system of the human species has transformed the way human beings carry out their cognitive business, both individually and collectively.