They also believe that the network knows more about them than they do about themselves. This is an extension of the sense of paranoia felt by many people in the 1970s, believing themselves to be powerless in the face of political and economic forces over which they had no control. Perception is a recurrent theme in the novel. In particular, Brunner is concerned with perceptual patterns and how they can both help and mislead. Nick projects patterns of behaviour to assume his personas, but Kate has "natural wisdom" which means that she ignores surface patterns to perceive the truth beneath. When they arrive in Precipice, the couple have to abandon their normal "urban pattern" to see the ways in which the town's unique design merges public and private space, along with natural and artificial structures. The theme of patterns in perception runs through the entire novel. Future shock arises when reality and change disrupt patterns. People respond by falling into strong patterns within human nature, particularly tribalism. Others try to convince themselves that all change is good, adopting the "plug-in" lifestyle where they feel able to relocate to another city and insert themselves into a new social niche with a minimum of inconvenience. Their mobility is, however, a reflection of the failure of the lifestyle to satisfy them, resulting in more moves. In this world of confusion are also companies specialising in psychological intervention. One such is Anti-Trauma Inc. which is hired to "normalise" children in a process akin to deprogramming, the (often violent) attempt to force people to renounce their association with groups perceived as cults. Anti-Trauma does significant harm to its charges, although as so often happens in Brunner's interconnected society, it also spends much money and time covering up its failures. The worm Brunner's concept of the computer worm was inspired by analogy with the tapeworm, a digestive parasite. A biological tapeworm consists of a head attached to a long train of reproductive segments, each of which can produce more worms when detached. Brunner's "data-net tapeworm" consists of a head followed by other segments, each being some kind of code which has effects on databases and other systems. Several are unleashed in the book. Besides the two Hearing Aid tapeworms, and Nick's ultimate tapeworm, there is a "denunciation tapeworm" created as revenge by a representative of Anti-Trauma Inc. whom Nick insults and curses. At the time, Nick