Why double dissociations don't mean much

The conventional interpretation of double dissociations is that they are almost irrefutable evidence of distinctions in both function and type of mental processes, or of separation of cognition into modules. We present a connectionist model that demonstrates apparent double dissociations within a single-route, single-mechanism network and argue that these apparent dissociations are simply the expected tails of a standard bell curve describing network performance. We conclude that within a connectionist model, the appearance of double dissociations may not be evidence for functional or mechanistic separation, and that similar caveats apply to the interpretation of double dissociations in human cognitive behaviour