Why does “I was happy to do my homework” work, but “I was tired to do my homework” doesn’t?

I’m teaching ESL, and I came across a question from one of my students that I don’t know how to answer. Using the form “{subject} {verb} {adjective} {infinitive phrase}” we’ve been going over sentences such as “I was happy to help you.” (More specifically, “I helped you. I was happy. -> I was happy to help you.”)

One of my students then suggested “I was tired to do my homework.”

Now, as a native English speaker, I know that this is wrong. I’m even college educated and actually trained in ESL (which included grammar classes)… and yet, I have no idea WHY this is wrong. It SEEMS to fit the form our textbook was teaching (“I did my homework. I was tired.” -> “I was tired to do my homework.”) and yet I know it’s wrong.

What’s the difference? Why doesn’t this work?

Answer

Let’s change the main verb to “see”. All the following adjectives accept an infinite

  1. I was happy to see her

  2. I was sorry to see her

  3. I was surprised to see her

  4. I was disappointed to see her

5a . I was sad to see her (go)

5b. I was saddened to see her

‘I was saddened to see their lack of commitment.’

  1. I was mad to see her

Incidentally, mad in British English usually means “crazy”, so the speaker could be complaining:
“I must have been mad to see her, whatever was I thinking?”

  1. I was impatient to see her

  2. I was anxious to see her

BUT NOT

  1. I was bored TO SEE her
    • I was bored of seeing her
    • I got bored seeing her

Similarly, it is equally ungrammatical to say: “I was bored to do my homework”
Google Books has innumerable results for bored to death, and bored to tears but none for was bored to do and only 4 instances for was bored to see And yet, bored is also a feeling or an emotion. A handy list of adjectives ending in -ed and -ing which may help the OP in his ESL lessons

  1. I was tired TO SEE her
    • I was tired of seeing her
    • I got tired seeing her

In sentence number 10, the speaker probably wanted to say they were too tired to meet someone, “too” often carries a negative meaning.

I was too tired to do my homework

As a result, I didn’t do my homework.

However, using tired alone (without the adverb too) works as the reason for doing or not doing something.

  • He was tired to go to bed
  • He was tired, so he went to bed
  • We were tired to stop for a rest
  • We were tired, so we stopped for a rest
  • She was tired to see him
  • She was tired, so she didn’t see him
  • I was tired to do my homework
  • I was tired, so I didn’t do my homework

The same is true for the following synonyms of tired: weary, exhausted, sleepy, drained, burnt-out / burned-out.


REVISED
I found an interesting older question on EL&U which mentions the usage of infinitives after adjectives. It doesn’t specifically answer the OP’s question but I consider it useful nevertheless.

To infinitive used after adjective.

The following is a short excerpt from @Araucaria’s answer.

Adjectives which take infinitival phrases as complement fall into three camps.

  1. Some adjectives determine our interpretation of the subject of the infinitival clause.
  2. Some adjectives determine our interpretation of the object of the infinitival clause.
  3. Some adjectives don’t determine our interpretation of either the subject or the object of the infinitival clause.

Group 3

Some adjectives don’t fall into groups 1 or 2. We can’t use them as predicate adjectives when they have an infinitival clause as complement. That is to say we can’t use such adjective phrases as Predicative Complements. One of these adjectives is the word possible:

  • *A Rubik’s cube is possible to be done.
  • *Pineapples are possible to grow here.
  • *Whales are possible to swim.

These sentences are ungrammatical. They are odd because they seem to be verging on the grammatical, but just don’t seem to quite work properly.

Addendum

Many users have repeatedly pointed out (see comments) that the adjective annoyed is used with the to-infinitive. The following pattern, ANNOYED AT + GERUND as in: I was annoyed at doing my homework, sounds far better to my ears; however, after searching a bit, I did find a few examples in the Oxford Learners’ Dictionaries of annoyed + to-infinitive (to my consternation ☺).

Attribution
Source : Link , Question Author : Richard Winters , Answer Author : Community

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