How can I get the title attribute from get_the_post_thumbnail()?

post_excerpt is actually the caption attribute. Here is the correct answer:

$title = get_post(get_post_thumbnail_id())->post_title; //The Title
$caption = get_post(get_post_thumbnail_id())->post_excerpt; //The Caption
$description = get_post(get_post_thumbnail_id())->post_content; // The Description