Transparency is a fun concept, as applied in the recent philosophical literature on self-knowledge (e.g., here; see also these past posts). I want to extend the transparency metaphor to self-knowledge of personality traits, where philosophers haven't yet taken it (to my knowledge).
First, the established versions:
Transparency 1: Sensory experience. As G.E. Moore and Gilbert Harman have noticed, when you try to attend to your visual experience you (usually? inevitably?) end up attending to external objects instead (or at least in addition). Attend to your experience of the computer screen. In some sense it seems like your attention slips right through the experience itself, lodging upon the screen.
Transparency 2: Attitudes. As Gareth Evans notices, when someone asks you if you think there will be a third world war, you typically answer by thinking about the outside world -- about the likelihood of war -- rather than by turning your attention inward toward your own mental states. More contentiously, thinking about whether you want ice cream also seems to involve, mostly, thinking about the world -- about the advantages and disadvantages of eating ice cream.
In both types of case, you learn about yourself by attending to the outside world. One feature of this metaphor that I especially like is that you can learn about distortions in yourself by noticing features of the world that don't align with your general knowledge. Gazing through a window, if the trees are a weird color, you know the window is tinted; if the trees wiggle around as you shift head position, you know the window is warped. If the lamplights at night radiate spears, you've learned something about distortions in your vision. If your paper is The Best Thing Ever Published, you've learned something about your egocentric bias.
This brings me to:
Transparency 3: Personality. Since I think personality traits and attitudes are basically the same thing, I regard Transparency 3 as a natural extension of Transparency 2. (And since 2 and 1 are also related, maybe we have 1 3/4 kinds of transparency rather than three kinds.) To find out if you're the kind of person who loves children, think about children. To find out if you're an extravert, think about parties. Since your personality colors your view of the world, one way to learn about your personality is to look at a relevant part of the world and notice its color. (You can also consider your past behavior; or directly try a label on for size; or ask friends for their frank opinion of you. Transparency-style reflection on the world isn't the only, or even always a very good, route to self-knowledge.)
This approach might work especially well for the "Big Five" personality trait Agreeableness. "Agreeable" people are those who self-rate, or are rated by others, as being concerned for other people, interested in them, sympathetic, helpful. Several recent studies suggest that people who self-rate as agreeable tend also to be more likely to rate others as agreeable (sympathetic, helpful, etc.), and also to rate other people positively in other ways too, especially if the other person is not very well known. If you're a sweetheart, the world seems to be full mostly of sweethearts and interesting people; if you're a jerk, the world seems to be full of jerks and fools. What I'm proposing to call the transparency approach to self-knowledge of personality simply involves running this observation the other direction: From the fact that the world seems full of uninteresting and disagreeable people, infer that you are a disagreeable person; from the fact that the world seems full of warm, loving, interesting people, infer that you are a relatively sympathetic, concerned person.
Now it would be really interesting if it turned out that these sorts of perceiver effects were actually better predictors of underlying personality as constituted by patterns of real-world behavior than are the typical self-rating scales used in personality psychology -- but it's probably too much to hope that the world would align so neatly with my own theoretical biases. (Hm, what does that last judgment reveal about my personality?)