“About 80 students were invited to participate in an experiment and were told they would be given some money after a series of tests. A researcher was hired and made the students dislike him by being rude to them. The students took the tests and were all awarded the promised money. They were then divided into three groups. . . . “
* source; from our local textbook
While I understand ‘be told’ and ‘hear’ are frequently interchangeable in many contexts, but in this one above I feel the replacement with ‘heard’ would be a little awkward, since ‘were told’ implies ‘a direct conversation between you and someone’ and ‘heard’ does ‘an indirect becoming to know something, like you saw it on TV, or read it in the newspaper, etc.’
I would appreciate it, if I have your valuable opinions on this matter.