Gentlemen!

Study of remembered visual images taught us that they are acquired associations of perceptual elements of the central projection field, and that, for these, the form [Ed] of the stimulus is crucial. You would be justified in transposing this principle to central projection fields of any sensory region. Acquisition of such memory images is generally based on a feature of central projection fields—their perceptual elements, that is, those nerve cells connected directly with projection fibres and also interconnected by association fibres, separate for each projection field. We shall speak in future about olfactory, acoustic, tactile and gustatory memory images without going into further detail about their nature. I need not draw attention to the fact that each sensory area presents its own particular problems [1], and that these simplest mental components, the remembered images, can be more complex in form.

Recognition—or primary identification—is produced by virtue of this property of memory images. If, for sake of simplicity, we restrict ourselves to solid objects, which by themselves make up central aspects of sensory perception, the content of consciousness is made up of the sum of such remembered images of these solid objects. Clearly, within this sum, certain fixed groupings can likewise be differentiated, always corresponding with the features of a particular solid object. One and the same solid object usually contributes to several sensory perceptions, always recurring in the same manner. The simultaneity of these several sensory inputs leads to their remembered images remaining in association. In this manner an acquired association of memory images from different senses corresponds with each solid object, and the association is progressively consolidated the more frequently the same solid object is perceived by our senses. Thus we find an anatomical basis for those psychological dimensions that have traditionally been used to describe ‘concepts’ [W]. We are now in a position to differentiate the ‘strength’ [Ed] and ‘extent’ [Ed] of the concept; however we will distinguish essential and non-essential features of solid objects depending on whether they always adhere to the object or are changeable. Of course, the extent of a concept includes its non-essential characteristics, since these always show a degree of constancy depending on the nature of the object. For any item, we can then easily plot a curve with Extent (‘circumference’ [Ed] of the item), entered along the x-axis and ‘Intensity’ [Ed] (or strength) of the concept/item on the y-axis.

We have just seen how secondary identification differs from primary identification, in that when each individual component of a concept is excited, the sum of all the rest, making up the whole concept, can be excited. The anatomical basis for acquiring such related functional groupings of cellular elements is the availability of association fibres between the various projection fields. We shall call these ‘trans-cortical association pathways’ [Ed], in contrast to intra-cortical intrinsic fibres. The content of consciousness, as we now recognize, therefore includes the concept [Ed] of solid objects or, as we will call it, concrete concepts [Ed]. We can also identify the sum of such concepts as consciousness of the outside world [W], for in these concepts we in fact possess a true picture of the outer world.

As you will notice, also included in consciousness of the outside world is the apparatus for ‘simple circuit operations’ [Ed]. This process is the same as that which also serves for secondary identification. From audible speech, from the barking of a dog, or from a certain fragrance I can acknowledge the presence of a man, a dog, or a certain flower. Virtually all circuit operations which relate to concrete features are similar, and therefore, as we have seen, are only isolated examples of secondary identification.

The content of consciousness thus consists not only of memory images, but also secondarily of fully-defined complexes [Ed] of such images firmly linked to one another through association—concrete concepts. The number of concepts depends on the number of solid objects. Perhaps you are astonished that I have so far presented it as though only a few (and always the same) objects would enter our sensory world. You might ask: Do not things in the outer world come into the realm of our senses in almost infinite number and indescribable multiplicity? Fortunately, a specific answer is possible. The number of words gives us a clue to the number of concepts. The number of concepts that a particular individual possesses is shown by the number of words with which he functions. One of the most comprehensive spirits who ever lived, or will ever live, is, undoubtedly, Shakespeare; accordingly, his vocabulary is also uncommonly comprehensive: extending to 15,000 [2]. How much should we subtract from this, if we want to restrict ourselves to solid objects of the outside world! Not everyone is a Shakespeare, but you will be surprised when we soon pass to the other extreme (amongst civilized nations!): The vocabulary of an English seaman does not exceed a few hundred. The number of concrete items is, in fact, not so great, nor is their diversity so significant, as we can easily appreciate, especially when we realize that the number of nerve cells in the cortex is about a Milliarde [W] by Meynert’s count. We can now grasp that indeed the same solid object must impinge on our senses quite often, if such a firm connection is to exist of particular remembered images with what we call ‘concepts’ [W].