Mental verbs act somewhat differently than active verbs. Some of the main differences are:
1) Most mental verbs are not used in progressive tenses.
2) When mental verbs, such as: see, hear, smell are used in the progressive, their meanings may be different from when they’re used in the simple tenses.
3) While mental verbs can be used with –USED TO to talk about past habits, they cannot be used with WOULD to talk about past habits.
4) Mental verbs are usually used with the present perfect rather than the present perfect progressive to talk about states that started in the past and continue to the present.