Russ pointed out that Uri can simply return the envelope that the experimenter gave him, thus ``guessing" correctly at every experiment.
To remove these doubts, Mr. Tachman suggested to reverse the case where a success is declared, i.e. if the bit in the envelope he gives the experimenter is the opposite of the one the experimenter chose, then he guessed correctly. This satisfied Russ.
Uri Tachman did not claim perfect telepathy, so a relatively large number of experiments should be conducted in order to get a statistically significant result. He therefore suggested a mechanism to save time: the experiments would be executed in pairs, where in each round the experimenter would give Uri two envelopes (left and right) and receive in return two envelopes (corresponding to left and right). The round would be considered a success for Uri only if for both the left and the right envelopes the bit in Uri's corresponding envelope is the opposite of the experimenter's bit.
Uri claimed that since a random guess gives him a 1/4 chance of succeeding in a round, then winning in significantly more than a quarter of the rounds implies that he has demonstrated his psychic powers.
What do you think? Click here to see what Russ thought of it.