Let's read Attention and consciousness (2006), Christof Koch and Naotsugu Tsuchiya

Attention and consciousness: two distinct brain processes (2006), Christof Koch and Naotsugu Tsuchiya. This paper argues that attention and consciousness are different.

This paper in an expanded format is viewable on Scholarpedia.

Attention in this paper always means "selective attention". Think of it as "shining a spotlight" on something, like a face, a melody, a word. It does not mean general arousal and alertness.

We argue that events or objects can be attended to without being consciously perceived. Furthermore, an event or object can be consciously perceived in the near absence of top-down attentional processing.

Function of attention

Attention is useful because we sense more than we can process.

In primates, about one million fibers leave each eye, carrying on the order of $1MB/sec$ of raw information... attention ‘selects’ information of current relevance to the organism, while the non-attended data are neglected.

We select what we attend to based on outside and inside cues. Some things are inherently "eye-catching", "visually salient", and they induce bottom-up selective attention. Visual saliency is so well-understood that there are programs that can calculate it. This is used by visual designers to manipulate viewers' eye motion. You bet the ad designers would want to do that.

Sometimes we have top-down attention, say, when we are looking for Wally (feature-based attention), or staring at a piece of art (object-based attention), or looking at a general location in space (focal attention).

feature-based attention

Object-based attention

Focal attention (only one of them did it)

Bottom-up attention is clearly unconscious. This article only considers top-down attention, and will argue that it's different from consciousness.

Functions of consciousness

The paper listed these as functions of consciousness, without justification, but seems like a good guess. Unconscious people certainly can't do these.

• summarize relevant information
• advise the planning areas of the brain
• detect anomalies and errors
• decision making, 
• language
• inferring the internal state of other animals
• setting long-term goals
• making recursive models 
• rational thought

4 kinds of visual percepts and behaviors

Attention with consciousness

• Working memory
• Detection and discrimination of unexpected and unfamiliar stimuli
  [Inattentional Blindness (Mack and Rock 1998)  demonstrated compellingly that subjects must attend to novel or unexpected stimuli to become conscious of them]
• Full reportability [the subject can talk about what they saw]

Those are quite intuitive.

... these mechanisms must involve a reciprocal relationship between cellular populations in extrastriate visual cortices and neurons in the premotor and prefrontal cortices, mediated by long-range corticocortical feedforward and feedback projections.

Too much jargon. What it's saying is just that, the brain hardware necessary for seeing with attention and consciousness are back-and-forth cables connecting between the visual cortex and the premotor and prefrontal cortexes. There can't be just a one-way communication, they must talk with each other.

Without consciousness without attention

• Formation of afterimages 
• Rapid vision (<120 ms)
• Zombie behaviors

What are "zombie behaviors"? They are behaviors that are complicated, but done "automatically", without thinking.

As anybody who runs mountain trails, climbs, plays soccer or drives home on automatic pilot knows, these sensorimotor skills – dubbed zombie behaviors – require rapid and sophisticated sensory processing. Confirming a long-held belief among trainers, athletes perform better at their highly tuned skill when they are distracted by a skill-irrelevant dual task (e.g. paying attention to tones) than when they pay attention to their exhaustively trained behaviors.

It actually feels great to be a zombie, according to elite athletes who can stay zombie for hours at a time (though they tend to call it "flow").

Attention without consciousness

• Priming
• Adaptation
• Visual search
• Thoughts

Priming is a famous effect, so I won't say more. I just did a Youtube search "priming" and amusingly it's full of motivational speeches that are supposed to prime the viewer to face the day with SUCCESS (also, their thumbnails are all stereotypically strong men... I feel there's some kinda bias there).

Print this out and look at it every time you wake up. Priming!

Koch noted that priming works even for blindsight people, who cannot have any conscious vision. This is further evidence of attention without consciousness.

Consciousness without attention

• Pop-out in search
• Iconic memory
• Gist 
• Animal and gender detection in dual tasks
• Partial reportability

When we pay total attention to the center of a scene, what we see in the peripheral is very blurry, but we still feel, in the consciousness, a full scene. This is consciousness without attention.

Gist:

gist is immune from inattentional blindness: when a photograph covering the entire background was briefly flashed [30 ms] completely unexpectedly onto a screen, subjects could accurately report a summary of what it contained.

Dual task: inattention by design. The subject’s attention is paid to central task, while at the same time a secondary stimulus is flashed in the periphery. 

With focal attention busy at the center, subjects can determine whether a scene contains an animal (or a vehicle) but are unable to distinguish between a red–green and a green–red disk... Likewise, subjects can distinguish between male and female faces in the periphery or even between famous and non-famous faces. However, remarkably, subjects are frustrated by tasks that are computationally much simpler (e.g. discriminating between a rotated ‘L’ and a rotated ‘T’).

So it's perception without attention. Is it consciousness? Yes.

they can be confident of their discrimination choices and ‘see’, albeit often indistinctly, the peripheral stimuli.

I would add another example: when reading, I often have a clear consciousness of something odd has happened, and upon reading again, I find that there was a typo. I was not paying any attention to typos, but the consciousness of typo still happened.

Attention and consciousness can go against each other

When observers try to find two embedded targets within a rapidly flashed stream of images, they often fail to see the second target.

This is the attentional blink:

a series of letters and numbers are flashed on a screen in a rapid sequence. The viewer is asked to look for a specific pair of items, such as the number 2 and 7 and press a button when they spot the target numbers. In many cases, observers fail to see the second target when it occurs soon after the first one.

Counterintuitively... observers can see both the first and the second targets better when they are distracted by a simultaneous auditory dual task or when they are encouraged to think about task-irrelevant events.

That's one way attention (looking for targets) can inhibit consciousness (become aware of targets).

Do these conclusions hold for real life?

YES. They are not just lab curiosities.

A lasting insight into human behavior – eloquently articulated by Friedrich Nietzsche – is that much action bypasses conscious perception and introspection.

Oh wow Nietzsche! 

Actions are never what they appear to us to be! We have expended so much labour on learning that external things are not as they appear to us to be—very well! the case is the same with the inner world!  -- Daybreak, Nietzche

Doubts about whether perception and introspection accurately find the cause for our own actions were expressed before Nietzche:

Newton was able to separate the colors. Which name will the psychologist have who tells us what the causes of our actions are composed of? Most things, when they become noticeable to us, are already too big. -- Georg Christoph Lichtenberg

For more on Nietzsche, see Inner Opacity. Nietzsche on Introspection and Agency (2015), Mattia Riccadi.