Grammatical pattern: it + VERB + somebody + when + CLAUSE

The above example has the same basic meaning as “Each time I forget things, it bothers me.”  It is similar in meaning to the construction “Forgetting things bothers me,” but it is not exactly the same--the clause ”when I forget things” refers to the separate times of forgetting and the reaction it causes each time, not just to forgetting in an abstract sense as something people do.

In this pattern, the word “it” is the grammatical subject of the sentence although it has no real meaning. The action or condition expressed in the when-CLAUSE in these types of sentences is, in fact, what causes the emotion in the verb (i.e., annoyance, fear, worry, confusion, pleasure, etc.)  It is the forgetting that causes the annoyance, in our example. The when-CLAUSE is, therefore, the notional subject of the sentence.  However, the when-CLAUSE in this pattern would not generally be considered acceptable as a grammatical subject by English speakers.  In other words, the sentences below with the when-CLAUSE in the subject position would seem ungrammatical or unnatural to most people.

*When you make that noise irritates me.
*When she talks like that confuses us.
*When he did that shocked everybody.

The above sentences would be considered normal and correct, if they included the word “it” as the subject in them, as in the following sentences.

When you make that noise, it irritates me.
When she talks like that, it confuses us.
When he did that, it shocked everybody.

Note that the pattern under discussion here [it +  VERB  +  somebody  + when + CLAUSE] is the same as that in the above three examples. The when-CLAUSE can be placed either initially or toward the end of the sentence.

Verbs that follow the pattern  [it +  VERB  +  somebody  + when + CLAUSE]

amaze, anger, annoy, bother, bug, concern, confuse, delight, disgust, distress, disturb, embarrass, excite, frighten, frustrate, humiliate, hurt, irk, irritate, perplex, please, puzzle, scare, shock, stun, surprise, terrify, thrill, trouble, unsettle, vex, worry

Additional examples of the pattern  [it +  VERB  +  somebody  + when + CLAUSE]

It excites me when I think about the future.

It frightens him when he loses his balance.

It pleases his mother when he sends her a card on her birthday.

It disgusted me when I saw what was under the sink.