There is such a thing as a depth error. Normally a depth error is one that is made by a therapist and is comprised of finding an issue with a client that does not really exist and is in fact most likely more projection (or countertransference) on the part of the therapist. Depth errors occur because a therapist tries to assume too much from a relatively innocuous set of circumstances or a turn of phrase that a client uses.
I personally vacillate something fierce on the depth of humans to begin with. Part of me does think that there has to be much more going on under the surface of our conscious mind than what we are immediately aware of. I do not think that we can say that humans are only stimulus-response animals. To say this would rule out values, convictions, and opinion. These three things, I think frequently live in the unconscious or the preconscious are, unless they are brought up in the environment and are the main topics of conversation. Reaction is one of the best examples of the unconscious. If this didn't exist, then everyone would react the same (or similar) in most situations. When an external stimulus is provided, we "choose" our reaction after searching or files based on our values, convictions, and opinions. Due to the sheer variability in different reactions, it shows that there is more to a person than just their animal instinct.
The other side of the coin is the argument not necessarily against the unconscious, but rather a more shallow conscious. I have to confess that I get frustrated sometimes with how shallow people are; that is, I get frustrated with how similar people can be. Sometimes it seems like there really is a lack of thought with some clients that makes a depth error rather frequent.