A student read the sentence, “The reports collected during the survey reveal a change in local habits,” and treated collected as the main verb. She then could not explain why reveal was present. Her tutor asked her to locate the noun before collected and test the hidden relation: the reports were collected. This made collected a past participle modifying reports. The finite verb was reveal, which agreed with the plural subject reports. In a second sentence, “Volunteers collecting the reports work in pairs,” the volunteers performed the collecting, so the present participle collecting modified volunteers while work served as the finite verb. The surface endings differed, but the same check solved both sentences: identify the noun, decide whether it performs or receives the action, and then find the verb that carries tense and agreement. Marking every -ing or -ed form as a main verb would create extra predicates that the sentence does not contain.