Investigating the stream of consciousness

25 May 2016 | Oliver Rashbook-Cooper (University of Oxford)

There are a number of different ways in which we can fruitfully study our streams of consciousness.

We might try to provide a detailed characterisation of how conscious experience seems ‘from the inside’, and closely scrutinise the phenomenology. We might try to uncover the structure of consciousness by focussing upon our temporal acuity, and examining when and how we are subject to temporal illusions. Or we might focus upon investigating the neural mechanisms upon which conscious experience depends.

Sometimes, these different approaches appear to yield contradictory results. In particular, the deliverances of introspection sometimes appear to be at odds with what is revealed both by certain temporal illusions and by research into neural mechanisms. 

When this occurs, what should we do? We can begin by considering two features of how consciousness phenomenologically seems.

It is natural to think of experience as unfolding in step with its objects. Over a ten second interval, for instance, I might watch someone sprint 100 metres. If I watch this event, my experience will unfold over a ten second interval. 

I will hear the pistol fire, see the race begin, and so on, until I see the leader cross the finish line. My experience of the race has two features. 

Firstly, it seems to unfold in step with the race itself, secondly it seems to unfold smoothly — it seems as if I am continuously aware of the race, rather than my awareness of it being fragmented into discrete episodes.

Can this characterisation of how things seem be reconciled with what we learn from other ways of investigating the stream of consciousness? To answer this question we can consider two different cases: the case of the colour phi phenomenon, and the case of discrete neural processing.

The colour phi phenomenon is a case in which the presentation of two static stimuli gives rise to an illusory experience of motion. When two coloured dots that are sufficiently close to one another are illuminated successively in a sufficiently brief window of time, one is left with the impression that there is a single dot moving from one location to the other (examples can be found here and here)

This phenomenon generates a puzzle about whether experience really unfolds in step with its objects. In order for us to experience apparent motion between the two locations, we need to register the occurrence of the second dot. This makes it seem as if the experience of motion can only occur after the second dot has flashed, for without registering the second dot, we wouldn’t experience motion at all. 

So it seems that, in this case, the experience of motion doesn’t unfold in step with its apparent object at all. If this is right, then we have reason to doubt that experience normally unfolds in step with its objects, for if we can be wrong about this in the colour phi case, perhaps we are wrong about it in all cases.

The second kind of case is the case of discrete neural processing. There is reason to think that the neural mechanisms underpinning conscious perception are discrete (see, for example, VanRullen and Koch, 2003). This looks to be in tension with the second feature we noted earlier – that our awareness of things appears to be continuous. As in the case of colour phi, it might be tempting to think that this tells us that our impression of how things seem ‘from the inside’ is mistaken.

However, when we consider how things really strike us phenomenologically, it becomes clear that there is an alternative way to reconcile these apparently contradictory results. We can begin by noting that when we introspect, it isn’t possible for us to focus our attention upon conscious experience without focussing upon a temporally extended portion of experience – there is always a minimal interval upon which we are able to focus.

The claims that experience seems to unfold in step with its objects and seems continuous apply to these temporally extended portions of experience that we are able to focus upon when we introspect. If this is right, then we have a different way of thinking about the colour phi case. 

On this approach, over an interval, we have an experience of apparent motion that unfolds over the time it takes the two dots to flash. The phenomenology is, however, neutral about what occurs over the sub-intervals of this experience.

The claim that this experience unfolds over an extended interval of time isn’t inconsistent with what goes on in the colour phi case. The apparent inconsistency only arises if we think that the claim that experience seems to unfold in step with its object applies to all of the sub-intervals of this experience, no matter how short (for development and discussion of this point, see Hoerl (2013), Phillips (2014), and Rashbrook (2013a)).

Likewise, in the case of discrete neural processing, in order for the case to generate a clash with how experience appears ‘from the inside’, our characterisation of how consciousness seems must apply not only to some temporally extended potions of consciousness, but to all of them, no matter how brief. Again, we might question whether this is really how things seem.

While experience doesn’t seem to be fragmented into discrete episodes, this certainly doesn’t mean that it seems to fill every interval for which we are conscious, no matter how brief (for discussion, see Rashbrook, 2013b). As in the case of the colour phi, perhaps our characterisation of how things seem applies only to temporally extended portions of experience – so the deliverances of introspection are simply neutral about whether conscious experience fills every instant of the interval it occupies.

There is more than one way, then, to reconcile the psychological and the phenomenological strategies of enquiring about conscious experience. Rather than taking non-phenomenological investigation to reveal the phenomenology to be misleading, perhaps we should take it as an invitation to think more carefully about how things seem ‘from the inside’.


Hoerl, Christoph. 2013. ‘A Succession of Feelings, in and of Itself, is Not a Feeling of Succession’. Mind 122:373–417.

Phillips, Ian. 2014. The Temporal Structure of Experience. In Subjective Time: The Philosophy, Psychology, and Neurscience of Temporality, ed. Dan Lloyd and Valtteri Arstila, 139–159. MIT.

Rashbrook, Oliver. 2013a. An Appearance of Succession Requires a Succession of Appearances. Philosophy and Phenomenological Research 87:584–610.

Rashbrook, Oliver. 2013b. The continuity of consciousness. European Journal of Philosophy 21:611–640.

VanRullen, Rufin. and Koch, Christoph. 2003. Is perception discrete or continuous? Trends in Cognitive Sciences 7:207–13.