ABSTRACT
In common parlance, “remembering” something consists of associating an idea or thought with a sensory cue. For example, someone may mention the name of a celebrity, and we immediately recall a TV series or newspaper article about the celebrity. Or, we may be shown a picture of a place we have visited and the image recalls memories of people we met and experiences we enjoyed at the time. The sense of smell (olfaction) can also elicit memories and is known to be especially effective in this way
It is difficult to describe and formalize these very high-level examples and so we shall consider a more mundane instance that, nevertheless, contains all the aspects of those above. Consider the image shown on the left of Figure 7.1. This is supposed to represent a binarized version of the letter “T” where open and filled circular symbols represent 0s and 1s respectively (Sect. 4.6.1). The pattern in the centre of the figure is the same “T” but with the bottom half replaced by noisepixels have been assigned a value 1 with probability 0.5. We might imagine that the upper half of the letter is provided as a cue and the bottom half has to be recalled from memory. The pattern on the right hand side is obtained from the original “T” by adding 20 per cent noise-each pixel is inverted with probability 0.2. In this case we suppose that the whole memory is available but in an imperfectly recalled form, so that the task is to “remember” the original letter in its uncorrupted state. This might be likened to our having a “hazy” or inaccurate memory of some scene, name or sequence of events in which the whole may be pieced together after some effort of recall.
