See Intentional Design for a discussion of the design stance and the intentional stance. In plain language, people act in an intentional way. For example, a person will consistently pursue some goal by whatever means available. In addition, we are often consciously aware of our intentions. This has led people to suppose that intention is a conscious process, and that if we observe a person acting in an intentional manner, we suppose that he has consciously arrived at that intention, and is now pursuing it.
Yet there is a great deal of puzzling evidence that conflicts with this model of conscious intention. We often perceive people's intentions as being different than the intention that they report, especially when they appear to be acting in a self-interested way. Also, people often struggle to explain why they are doing what they are doing, and may admit the importance of subjective motivations such as emotions and gut feelings.
Intentional Design says that we can regard people as being designed by evolution, so we can also regard their intentional behavior and their conscious awareness of their intentions as being designed to pursue the ultimate intention of survival and successful reproduction. If we are consciously aware of all of our intentional behavior, then we say that we have been designed for intentional transparency. If this is not always so, then there is intentional opacity.
What about the intentional design of humans under the evolutionary design stance? Is the intentional design transparent or opaque? On one hand, most people say they would like to have children someday, or if it's too late, have some regret that they didn't have children. On the other hand, humans spend almost all of their time pursuing intentions that they don't see as related to having children, and there are huge blobs of motivational opacity in the human psyche. Although people say that they do something “because I love her” or “because it's the right thing to do”, when pressed for the reason why they love her or why it's the right thing to do, they stop, and think, and generate some sort of plausible explanation. They have applied themselves to the intention of explaining their action (see The Interpreter Theory).
In short, we think there's a good case that humans are the victims of some perplexingly opaque intentional design. It is a form of Level Confusion to argue that humans are not designed to implement the intention of reproductive success because the humans don't have that intention. In fact, people's intentional motivations are so opaque that we can often predict people's behavior better using the intentional stance (taking reproductive success as their primary intention) than we can if we listen to what they are saying. For example, in mate choice the evolutionary intentional stance is better at predicting people's behavior than they themselves are at predicting their own behavior.
We observe humans as behaving in a certain way that seems adaptive, yet when we ask people about that sort of behavior, they are unaware of it, or deny it. This distortion of self-perception is similar to that in Positive Illusions. In the context of influence by mass media, this distortion has received some attention as the Third-Person Effect, where people expect that others are more influenced by media than they themselves are. See also The Third Person Effect.
How can there be this mismatch between conscious intention and behavior, and why is it this way? First, we must understand that (as the The Interpreter Theory proposes), intentional behavior is not primarily caused by conscious intention.
Although non-intuitive (see The User Interface Analogy), it is clearly possible for intentional (goal oriented) behavior to exist without conscious intention. First of all, non-human animals show intentional behavior, though few suppose that they are conscious in the human sense. Second, humans spend a great deal of their time “running on autopilot”, engaging in complex goal-oriented behaviors (such as driving) without any associated conscious intention.
The key point is that as long as people do behave adaptively it isn't necessary that they be aware of behaving adaptively. It is only necessary that their actual behavior be adaptive. When your dominant motivation is socially unacceptable (self-serving) it can even be adaptive to misunderstand yourself.
But if conscious intention doesn't cause behavior, then why are we conscious at all? The Argumentative Theory proposes that the purpose of consciousness is social coordination. Consciousness is a largely verbal process that exists to explain and justify our own behavior (see The Interpreter Theory) and to persuade others to behave in ways that are beneficial to us (and often to them as well).
Our conscious awareness of our intention may differ from what others might reasonably infer from our behavior. From an evolutionary perspective, it is deeply unsurprising to find that people conform strongly to social influences (see Conformity Bias) and engage in self-serving behavior. It is what we would expect because these behaviors are adaptive.
The evolutionary pressure on consciousness is different because the purpose of consciousness is to generate persuasive socially acceptable arguments. Social conformity and self-interest are not generally considered valid arguments in favor of a position. These behaviors are adaptive (and therefore necessary), but are not a legitimate basis for argument. Since it is not a legitimate basis for argument, it is useless or harmful for the interpreter to generate such an explanation, so we don't.
This mismatch between behavior and conscious intention is then an evolutionary adaptation to individual/group conflict. See also The Evolution and Psychology of Self-deception for the Evolutionary Psychology interpretation of this sort of behavior.