A cascade failure occurred when a "learning" program was corrupted, either by repeated application to a task it was ill suited to perform or by external influence such as damage to the hardware used to implement it. In a neural net system, in particular a positronic brain, in which most or all sub-programs interact, this could lead to corruption of surrounding algorithms and routines as they attempted to use data generated by the faulty application to perform a task of their own. This may compound the damage to the original sub-program, as neural nets tend to be referential in nature.