In the Hulk movies he is portrayed as a dumb monster. They made him look completely mindless. I am concerned about it because within the Marvel Cinematic Universe he barely talks.
All things being equal the character of the Hulk has had several permutations during his very long history where he did have the intellectual capacity of a five year old child. This is canon with the original premise of the Hulk as designed by Stan Lee and Jack Kirby in 1962.
Hulk is the alter ego of Bruce Banner, a socially withdrawn and emotionally reserved physicist who physically transforms into the Hulk under emotional stress and other specific circumstances at will or against it; these involuntary transformations lead to many complications in Banner's life. When transformed, the Hulk often acts as a disassociated separate personality that hates Banner. Over the decades of Hulk stories, the Hulk has been represented with several different personalities based on Hulk and Banner's fractured psyche, ranging from mindless savage to brilliant warrior, and Banner has taken control of the Hulk's form on occasion.
While this may be unsatisfying as a movie-goer, the character of the Hulk is not truly the central element in the Hulk storylines, Dr. Banner is.
This is most strongly seen in the early Hulk television series where the Hulk appears for five or ten minutes near the end of the show either to resolve violently a problem that generally could only be resolved with violence, or to screw up a potential friendship or relationship and cause Dr. Banner to move on.
Hulk Canon includes:
The Grey Hulk - transformed at night and reverted during the day, had some of Banner's intellect. This form would appear again many years later as Mr. Fixit.
The Green Hulk - abuse of the gamma machine which allowed him to control the Hulk's intellect lead to his Hulk persona growing more powerful and uncontrollable, spontaneously changing. His speaking was limited and memory impaired, almost never remembering what he did as the Hulk. In the early seventies, he had a moment of clarity when Jarella used magic to help him have Banner's intellect in Hulk's body.
The Savage Hulk - This is the Hulk most people are familiar with and the Hulk most seen in the first two Hulk movies. This Hulk has limited child-like intelligence, appears mostly when attacked and does everything in his power to escape conflict (after destroying what caused his transformation first).
The Professor - A version of the Hulk with Banner's intellect and the Hulk's abilities. During this time he worked with and eventually lead a group of metahumans called the Pantheon. It was during this time, Banner learned of an alternative future self known as the Maestro. The Professor appears to be the idealized version of the Hulk, all the power and all of the brains of his Banner form.
- Ang Lee's Hulk (2003) - Seemed to reprise the early wandering years of Dr. Banner as his transformations into the Hulk were random and highly destructive. The Hulk was an engine of destruction whose intellectual capacity was more of cunning than true displays of intellect.
Marvel's Cinematic Universe
The Incredible Hulk (2008) - Edward Norton reprises the role of Dr. Banner and the Hulk's role appears only a bit more intelligent than Ang Lee's Hulk. Banner's role is larger and Hulk smashes even more stuff. Unfortunately, smashing military vehicles is fun to watch but not very interesting after a while. Which lead to the development of the Hulk's character in the Marvel Cinematic Universe.
When the Hulk appeared in the Avengers, the Hulk appears to retain much more of the mind of Dr. Banner than either of the two earlier movies. He is still destructive and powerful, but now appears to have both more control and an ability to discern who to harm. This has happened in the comic canon several times. Two examples of the Hulk retaining his intellect and abilities as the Hulk have been as Mr. Fixit and as the Leader of the Pantheon.
It has been shown that the time spent by Dr. Banner in learning to control both his rage and the Hulk transformation allows him now to instantaneously transform and maintain at least some of his intellect while he is the Hulk. Whether that will continue remains to be seen.
In the history of Hulk he went from talking to being a monkey many time. You can see in this topic how this is a open converstion: http://marvel.wikia.com/User_blog:RiderJones/Since_when_could_the_Hulk_talk_right%3F
As one of the people there says:
The Hulk's intelligence and conversational prowess has changed multiple times over the years. It all really depends on who is writing him. You know, artistic license. Other times it's because some other factor relating to his mutation has effected the ol' brainpan. For example, there have been times the Hulk only got less articulate when he got mad, or he was bombarded by more Gamma radiation. There was at least four or five times that the Hulk retained the intelligence and mind of Bruce Banner (notably a pretty long stint in the early 90's when he as the "Professor") and the Grey Hulk has always been pretty smart, but very cruel.
In Avengers, Hulk does speak... "Puny God!" is uttered right after Hulk thrashes Loki soundly. I'd have to rewatch the recent Hulk movie (which leads into to Avengers) to be certain, but I seem to recall that he utters a few words there, as well.
Hulk, as a rage monster, is capable of speech, but has very little to say. The other problem is that if Hulk calms enough to be eloquent, he reverts to Banner...
... the telling comment comes from Banner, tho'; his control over his transformation is that "I'm always angry."
Even in the comics, Hulk generally is monsyllabic when he does speak. He's not, after all, Ben Grimm.
Talking Hulk is cool but RAGE is the word here. How many of us talk when angry? Rage is mostly expressed by violent action! The Hulk is not supposed to 'think out' a solution but to just smash everything. Smash the whole place up until that becomes the solution! I think talking weakens the big green guy's super power. However, speech makes him smart which means he becomes the most powerful superhero ever. Which means he can defeat Superman! Stab him with a green Kryptonite shard not try to beat the life out of him.
To answer the question body rather than the title, he was already established as more than a mindless brute in his first Cinematic Universe appearance, in 2008's The Incredible Hulk:
- 4:50 where uses one of the ripped-off metal sheets as a barrier against the sound waves.
- 6:30 where he protects Betty from the gunfire and crashing helicopter.