Tino Sehgal's installation, This Objective of That Object , is entered via a small vestibule linking two large, white, echoing rooms at London's Institute of Contemporary Art.
The silence is broken only by a deep, rhythmic breathing that morphs into guttural whispering and then a synchronised, repeated cry from the five "interpreters" (Sehgal's term), all of whom stand looking away from the viewers: "The objective of this work is to become the object of a discussion; the objective of this work is to become the object of a discussion."
Eventually, a viewer comments. In unison the interpreters shout: "A visitor has commented; who will answer?"
"I will," says one, and the comment is discussed, with occasional further comments from the braver visitors.
When a viewer enters, the process resets to the ostinato of the mantra-like slogan. Should no comment result, the interpreters slip silent and immotile to the floor, only to be awakened by the kiss of a comment.
There is no catalogue for this installation by the Berlin-based artist and radical conceptualist, who eschews writing to the extent of having only verbal contracts with galleries. So his intentions are far from clear, and the artspeak in the ICA's programme signifies nothing of an intriguing, fascinating, infuriating, sometimes beautiful, event.
The immediate impression is of profundity - the breathing, the chanting, the choreographed coordination of the interpreters.
Most visitors stay only five or ten minutes. But after an hour, the superficial, pseudo-oracular, pretentiously portentous responses impressed less, and became reminiscent of the platitudes, verbal tricks and Laingian word games of a group of pub bores.
The response to the comment, "Why?" was, "Why ask Why?"; "No, I want to hear your answer to Why?"; "Perhaps I don't have an answer". At times I thought of the computer program Eliza, which emulates a psychotherapist by randomly emitting phrases such as, "How long have you been feeling that?", "Why do you find that interesting?", or "Tell me more".
Sat cross-legged in a far corner of the room - and occasionally mistaken for a part of the installation - the fascination for me was in observing people who had inadvertently stepped into a giant social psychology experiment, finding themselves in a bizarre and unanticipated situation. Without exception, the viewers became silent, and communicated only through gestures, eye-movements and the odd surreptitious smile.
When an interpreter said: "The comment I heard was a sort of half-laugh", the belittling, superior tone inevitably reminded one of a schoolteacher responding to backchat.
The seemingly neutral term "visitor" eventually became a veiled threat, separating these Eumenides, the all-powerful interpreters with their undisclosed rules, from the disoriented, impotent victims, who entered expecting beneficence and enlightenment, and whose defence against the unknowable and unpredictable was silence.
Despite encouragement to violate art gallery conventions - to talk, to interact - in reality, the deterrent of an unknown humiliation prevented them.
The sinister undercurrents were those explored in Stanley Milgram's notorious social psychology experiments of the 1960s. Maybe I should return and comment that for evil to triumph all that is needed is for good men to stay silent?
Chris McManus is professor of psychology and medical education at University College London.