s) and vivid visual images created by the imagination.
This has all sorts of implications for cognitive science. One of the most interesting implications concerns the formation of "false memories," which are now at the forefront of the repressed memory debate. For instance, in a
Researchers have known for some time that producing visual images through imagination can sometimes lead to memory errors, called "reality-monitoring errors" because they fail to distinguish between observed and imagined images. Some of this is likely to be due to retrieval problems, but some also may be due to how visual images, be they imagined or produced by the senses, are encoded. What this study found is that when false memories, or reality-monitoring errors, were produced for words that had been presented without pictures (i.e., when these words were remembered as having been presented with pictures), the brain areas that were active during the study phase (most notably, the precuneus, right parietal, and anterior cingulate regions) overlapped significantly with those active during actual picture presentation. These areas were significantly less active during the presentation of words during the study phase in cases that were subsequently remembered correctly as having been presented without pictures. False memories were produced for study words about four times as often than for words that had not been seen in the study phase.
The lesson, then, is that contrary to Hume, during both in encoding and retrieval, there is often little difference between visual images created by the senses and those created by the imagination, even the images created of objects when reading the words that refer to them (which Hume specifically claims is impossible or at least uncommon). The difference is small enough as to make it difficult to distinguish between sensory and imagined images in memory. What, exactly, this means for the repressed memory debate will require further research, but it clearly demonstrates that there is a neural basis for false memories produced by repeatedly imagining images, for instance through repeated suggestions or rumination. Since we've yet to come up with anything like a neural, or even an algorithmic or representational basis for memory repression of dissociation, this sort of advancement in memory research certainly doesn't bode well for the champions of repressed memory theories and recovered memory therapies.