Excerpts from Suppes, Patrick, Bing Han, Julie Epelboim, and Zhong-Lin Lu. "Invariance of brain-wave representations of simple visual images and their names." Publications of the National Academy of Sciences, Psychology, 96. 25 (December 7, 1999): 14658-14663. Full text (external; subscription required).

The controversy about how the brain or the mind represents abstract ideas such as the general concept of a color or a circle, square, or triangle is older than psychology as an independent scientific discipline. Early in the 18th century, Bishop Berkeley (1710) famously criticized John Locke's theory of abstract ideas (1690). David Hume (1739, 17) later summarized succinctly Berkeley's argument. "A great philosopher [Berkeley] has disputed the receiv'd opinion in this particular, and has asserted, that all general ideas are nothing but particular ones, annexed to a certain term, which gives them a more extensive signification, and makes them recall upon occasion other individuals, which are similar to them." Berkeley's views are well supported by our results. After visual display of a patch of red or of a circle, the image is represented in the cortex by the brain wave of the word red or circle within a few hundred ms of the display and somewhat quicker than is the representation in the cortex of the spoken word red or circle. To the skeptical response that we do not really know it is the word red or circle that is being represented in the cortex, as opposed to the particular visual image, we respond that everything we have learned thus far about the one-dimensional temporal representation of words, presented either auditorily or visually, supports our inference, the spatial unidimensionality of the temporal representation used for recognition, above all. Perhaps just as important, the filtered brain waves representing the spoken color or shape words conform closely to the brain waves of the many other words whose brain waves we have identified in our earlier work.

There is much evidence that the memory of purely visual images decays quickly, almost always less than 200 ms ... [S]hort-term auditory memory lasts 2-5 sec ..., so it is most efficient to represent simple visual images in memory by the auditory representation of their names or simple descriptions. The brain-wave experiments reported here support in an unusually direct way that this is indeed what [happens, as] Berkeley and Hume conjectured long ago, but for different reasons than the brevity of visual memory.

References

1.  Berkeley, George (1710). Principles of Human Knowledge. Dublin: Jeremy Pepyat.
2.  Locke, John (1690). An Essay Concerning Human Understanding. London: Thomas Basset.
3.  Hume, David (1739). A Treatise on Human Nature. London: John Noon.

Contact:

Center for the Study of Language and Information
Ventura Hall, Stanford University, Stanford, CA 94305-4115.
E-mail: suppes@ockham.stanford.edu

Discussion
by Francis Steen

It is unclear that this study even addresses the referenced controversy between Locke and Berkeley, much less settles it. Berkeley suggested (in Hume's words) that "general ideas are nothing but particular ones, annexed to a certain term, which gives them a more extensive signification." This is not a topic addressed by the present study. Rather, what it addresses is that images, known to decay rapidly, can be and are usefully represented in the mind through words or word-like representations. The result is interesting but not what it is billed as.