An ongoing trend in technology policy has been to advocate participation. However, the author claims that lay citizens’ participation typically materializes in the form of a laboratory experiment at present. That is, lay participation as currently organized by professional participation experts under controlled conditions rarely is linked to public controversies, to the pursuit of political participation or to individual concerns. Derived from qualitative research on two citizen conferences, the author shows empirically that in practice, this laboratory participation leads to paradoxical (...) effects: successfully carrying out the experiment results in a systematic disappointment of the hope for gains in rationality typically attached to lay participation. Finally, the author relates this result to sociological debates about new modes of knowledge production. Under such a perspective, the author sees a paradoxical development: while society at large is becoming a laboratory in which knowledge is produced, participation practice is retreating from society into the lab. (shrink)