I’m afraid that the English textbook where you encountered those definitions got it all wrong about the present participle and past participle. Those definitions arise from a total—and I must say shocking—misunderstanding of what participles are, so it’s really no surprise that you found them confusing.
And, of course, you are absolutely right in not thinking that “nouns can cause adjectives.” This is a strange, even bizarre thing for that textbook author to say. Adjectives are not caused by nouns; by definition, adjectives are a part of speech that serves as modifiers of nouns to denote a quality of the thing named, to indicate its quantity or extent, or to specify a thing as distinct from something else.
That said, let me now proceed to clarify what a participle is to begin with.
Recall that the participle is one of the three English verbals, the other two being the infinitive and the gerund. These three are verb forms that function not as verbs but as other parts of speech. The infinitive and the gerund both function as nouns (whether as subjects, doers of the action, or objects in a sentence), but the participle generally can only function as an adjective.
The basic form of the participle is, of course, a verb that ends either in “-ing” or “-ed.” A participle that ends in “-ing” is a present participle, while a participle that typically ends in “-ed” is a past participle. Certain irregular verbs, though, form past participles that end in “-en” (as in “fallen”), “-d” (“shaved”), “-t” (“dealt”), or “-n” (“seen”).
So what does the present participle do? It expresses present action in relation to the time expressed by the operative verb of a sentence. For instance, in the example provided by the textbook author that you cited, “The crying baby in the airport caught the passengers’ attention,” the present participle “crying” functions as an adjective modifying the noun “baby.” It’s meant to convey the idea that the baby’s “crying” action took place at the same time as its having caught the passengers’ attention.
(Simply as a drill, the present participle is also at work in the following sentences: “The expanding balloon burst into flames.” “The nervous Senate witness ended up crying.” “Bantering, the two friends went home.” “He liquidated the company with his partners not knowing.”)
Now, what does the past participle do? In contrast to the present participle, the past participle expresses completed action in relation to the time expressed by the operative verb of a sentence. Take, for instance, this other example provided by that textbook: “The disappointed passengers went back home because of the airline’s flight cancellation.” Here, the past participle “disappointed” functions as an adjective modifying the noun “passengers.” It’s meant to convey the idea that the disappointment of the passengers over the airline’s flight cancellation had already taken place before their action of leaving the airport for home.
(Also as a drill, the past participle is at work in the following sentences: “They converted the demolished apartment into a warehouse.” “The fallen log was chopped into firewood.” “A comet is a rarely seen sight.”)
Regarding this incorrect example of present participle usage provided by that textbook, “The cried baby in the airport caught the passengers' attention,” it’s wrong not because the noun “baby” is or is not the one causing the adjective, but simply because what’s called for in this particular situation is the present participle “crying.”
In the same token, this incorrect example of past participle usage provided by that textbook author, “The disappointing passengers went back home because of the airline’s flight cancellation,” is wrong not because the noun “passengers” is or is not the one causing the adjective, but simply because what’s called for in this particular situation is the past participle “disappointed.”
Let me reiterate at this point that as you had correctly surmised, that textbook’s two rules for using the past participle or the present participle are absolutely false and absurd. And you are also correct in saying that their usage depends on the sense of the sentence. Indeed, from a semantic standpoint, it could very well be said that in the examples given, the past participle “disappointed” in “disappointed passengers” refer to their state of being, while the present participle “disappointing” in “disappointing passengers” refer to their behavior. From a grammatical standpoint, however, it’s more precise and instructive to say that the present participle applies when a present action is expressed in relation to the time expressed by the operative verb of a sentence, and that the past participle applies when a past action is expressed in relation to the time expressed by the operative verb of a sentence.
I trust that this discussion has adequately clarified that textbook’s alarmingly wrong instruction about the usage of the present participle and past participle.
