304 ◾ Biological Computation
9. How will increasing the activation threshold τ and the training
period impact the frequency of false alarms?
10. Why is it important for the match counter to decay over time?
11. Ideally, the immune system should not react at all in any situation
that does not pose a real risk. If that is impossible, one would want
the severity of the reaction to be proportional to the probability that
the situation poses a real risk. Suggest ways to achieve this in an arti-
cial immune system.
12. Discuss the possible disadvantages of the co-stimulation method used
by LISYS.
13. LISYS also uses another mechanism (not described in the text) that
allows each computer on the network to have a dierent sensitivity ...