The final part, though I might add something about some issues that have arisen in comments. Anyway, here’s the idea to be unpacked:
Introspective and perceptual attention rely in the same way on visual experience, namely the coupling of vision to cognition
Attention based Coupling
Let’s say something about coupling (I borrow the term from Alan Allport). Talk of coupling emphasizes a crucial role of attention. Elsewhere, I have written about the Many-Many Problem, the idea that to perform perception-guided behavior, we need to select some aspect of what we perceive to inform action. This selection for action, I claim, is a form of attention. In general, we can think of fixing beliefs about the external or internal world as often a goal-directed form of behavior.
Note that there is a Many Phenomenal Properties problem. A visual experience will exemplify many phenomenal features. Thus, to think about a specific phenomenal feature rather than others on the basis of introspection, one must select the feature, namely attend to it. We can then, for a given visual experience at a time, draw a space of possible introspective thoughts, each coupled with a specific phenomenal feature of the experience in question. Each potential introspective thought would be grounded in appropriate introspective attention to the phenomenal feature. The actual entertaining of a specific thought results from actually attending to the feature: so we have two modes of attention, the selectivity for cognitive attention, and cognitive attention (the thought) itself. In this way, visual experience is coupled, by introspective attention, to the relevant thought. For the direct theorist, so far, so good.
Let us now turn to visual attention that informs empirical thought. Here, we have the same structure as we saw in introspective thought, a space of experience based possible thoughts where attention functions to couple an input to thought: to think about the world on the basis of vision, we must exhibit selectivity of visible features of the world which informs our thoughts. Attention must again give rise to a coupling from visible features to thoughts about those features.
The upshot: in the space of possibilities for empirical and introspective thought, we have vision playing the same role. Visual experience is the basis of the vision-cognition coupling effected by attention, whether perceptual or introspective. You might call it the input, but that doesn’t sound the right note, so I won’t do so.
Both direct and transparency models of introspective attention can (and should) agree to this shared structure. Direct theorists, of course, will reject object-centered transparency, for they take the input to introspective attention to be a phenomenal feature whereas they take the input to perceptual attention to be the physical feature. The object-centered transparency theorist seems to say that the object of both forms of attention is the physical feature (but what of hallucinations!).
Shift now to the process-centered version of transparency, and focus on the shared structure noted above. Here, there is some empirical purchase on the issue and this is what I want to bring out. The process of visual attention is one of the most intensely studied of psychological phenomena, with much important work being done since the 1960s. While there are many controversies and confusions in this domain, I think attention is one of the better understood psychological capacities. We have lots of data that flesh out a picture of the mechanisms of attention. Thus, if we turn to the vision-cognition coupling, we have some good ideas of the mechanisms that underwrite it, both at the neural and psychological levels.
I don’t want to oversell our understanding of attention, for there is much work yet to be done. But let’s get a sense of the overall shape of vision-cognition coupling. What seems relevant is the selection of contents regarding the attended physical feature, F, such that those contents come to selectively inform cognition. At the level of mechanisms, the idea then is that the brain carries information about F (in whatever technical sense of “information” is of most use to neuroscience) where this information is selected to inform cognitive systems. This selection can be effected by a variety of mechanisms that have been discussed in the empirical literature: biased competition (up- and down-regulating signals when presented with multiple stimuli), receptive field remapping (filtering), gain modulation (amplification of signal), divisive normalization and so forth (I discuss this in a chapter on the neuroscience of attention in my forthcoming book).
Ok, so assume that we can identify this mechanism (or family of mechanisms) of the vision-cognition coupling which then explains how visual information is channeled for cognition. Call the mechanism of attentional selectivity N. N tells us how the relevant visual information about F is channeled so as to inform empirical thoughts about F.
Now: might it not be the same mechanism N that is deployed in introspective attention?
An Empirical Upshot and its (possibly) interesting Significance
I don’t know what the answer to the last empirical question is, but consider the affirmative answer. Then it seems that the transparency theorist has gained something by emphasizing the same-process version of transparency. For on the affirmative answer, the information used by N also underwrites the vision-cognition coupling that leads to introspective thought. That is, attention-based empirical thought and attention-based introspective thought share the same realization in terms of the visual basis that is coupled to thought. The first point then is that this mechanism is in a certain context C sufficient for attention-based empirical. That is, it is the basis for perceptual attention to features in the world that ground our thoughts about those features. The second point: in that same context C save with a shift in goals from fixing empirical thought to fixing introspective thought, N will be sufficient for attention-based introspective thought. Accordingly, the third point, there might be no additional mechanism of attentional selection beyond this shared basis in N. Specifically, there isn’t a form of attention that directly targets phenomenal properties. Rather, the form of attention at issue is one that deploys the mechanisms of vision-cognition coupling as exemplified in the perceptual attention case. We could talk about perceptual attention as the common element, but there are reasons I want to avoid this and simply speak about the same vision-cognition coupling.
The transparency theorist can leverage the empirical possibility we just noted to ask of the direct theorist what the realization of their model would be, a form of attention that targets a phenomenal property directly such that the property is embedded in introspective thought. This is pressing because if attention is something like a selective capacity, then N characterizes (realizes) this functional role. Accordingly, one can’t just talk about attention without some take on the realization, at least in principle. If the only basis for postulating such a distinctive capacity for attention is something like introspection (it’s obvious we can directly attend to consciousness), then I am deeply suspicious (though Dave Chalmers has some cases that might work, I will try to comment on them if time).
The direct model has another route. In the last post, I noted that the direct model can also be motivated by theoretical constraints from other areas of philosophy such as epistemology. In that sense, the direct model of introspective attention treats it as a theoretical postulate. For we seem to need something like introspective attention of the direct sort so that we can satisfy the various conditions that we impose on introspection: (a) its generating a distinctive way of thinking about the mind; (b) its privileged epistemic standing; (c) its distinctive first-personal aspect, and so on. [Josh Weisberg notes some other options in his comment in Part 1].
I don’t have answers to those admittedly weighty considerations. But here’s the crucial point that I want to emphasize. There are powerful epistemological constraints on the one hand that push us to certain views about introspective attention. These constraints have shaped our discussion for some time now [update: please see Brie Gertler’s helpful comment in part 1]. But if there is an open empirical question of the sort I noted above about N, then it is an empirical possibility that introspective attention is in a sense the same process as perceptual attention in that it relies on the vision-cognition coupling that N realizes, the functional role of perceptual attention. If that were true, then we can push in the other direction: might this now change how we should theorize about the epistemological and cognitive assumptions many philosophers have made regarding introspection and phenomenal concepts? For we would need to explain those phenomena without the idea of directly attending to phenomenal properties, that being a distinct process than the vision-action coupling we have noted.
Granting all that, then there is a way in which some of the central issues regarding introspection and consciousness have an empirical component, or at least that in principle, investigation of the underlying mechanisms might b. If I’m right, then while I can’t give a definitive answer whether N underwrites introspective attention, I can say that it behooves us to flesh out the transparency model in its process-based version and to see what its potential philosophical significance is, how it would reframe questions about the properties and structure of introspection and of phenomenal concepts. After all, for all we know, it might be true. This is the theoretically sound approach to a crucial issue both in philosophy and psychology: the nature of introspection and its epistemic status. It is clear, I hope, that reflection on attention plays a crucial role.