Imagine you are watching a dog (let’s say a black poodle called Pepper) running after her favourite tennis ball, the blackness of the fur and the shape of Pepper are bound together in our experience, and so is the yellow colour and circular shape of the ball while it’s flying through the sky. If Pepper barks the sound seems to come from her position and when the ball jumps along the road the sound of its bounce seems to originate from where it hit the road.
It seems obvious that our experiences should be like this. We would be surprised if the black colour of Pepper’s fur lagged behind the shape of Pepper so that it seemed to us as if a black fur-shaped blob tried to keep up with the fast movements of Pepper herself. We would be similarly surprised if we heard the sound of the bouncing ball lag the moment it seemed to bounce off the road.
Illustration by the magnificent @meapmaja
Yet, it is an incredible feat of the brain that makes sure that we do not experience this sequence of events where different features of objects aren’t coherently bound together as they change over time.
We are at all times bombarded with different stimuli features such as colours, textures, depth, sounds, tastes, and many more. These stimuli features occur at different times in the world and some also travel at different speeds (light travels faster than sound). So the signals we have to pick up hit different parts of our body at different times. These signals then have to travel from where we picked them up on the boundary surface of our body to be processed by the brain into the events we experience.
Keeping track of the timing of these different features only gets more complicated from here on.
The brain does not process whole events in a simple input-output fashion. Each moment in the event of looking at Pepper and the ball is not simply processed in whole momentary snapshots that are then experienced in sequence. The mechanisms responsible for sensory processing are temporally and spatially spread across the brain. This means that sensory information is processed in parallel sensory streams that are related to different sensory modalities (vision, hearing, etc.). Each of these channels is then subdivided into multiple parallel channels specialised for processing different sensory features (colours, edges, depth, shape, etc.). Each of these channels again consists of multiple serial processing stages.
All these processes and transmissions of sensory information take time and the amount of time varies significantly across channels. To perceive one moment of an event with all its features unified at a time, all these sensory streams must match up or be coordinated in some way, so that they single out the coherent sequences of events that we experience.
Let us call the problem of explaining how this incredible feat is accomplished ‘the temporal binding problem’. That is the problem of how we temporally bind sensory information that changes over time into the coherent sequences of events that we experience.
An efficient way to frame the ongoing debate about this problem is to frame it as a discussion about what ‘kind of time’ the temporal binding of stimuli is directed towards. We should distinguish between at least three kinds of time.
Firstly, we have subjective time. This describes the time as it is presented to us in experience. Secondly, we have event time. This describes the time at which events take place in the external world. Thirdly, we have brain time. This describes the time at which sensory processes occur in the brain.
Psychologists and philosophers that discuss the temporal binding problem disagree about how these three kinds of times are related. We can distinguish three broad views.
(1) Brain time views claim that the temporal binding of sensory information is directed towards the timing of neural events so that neural events that occur together in brain time are represented as occurring together in subjective time (see Kopinska & Harris). This means that if a sound is processed at the same time as a visual flash, then the fact that these two neural events cooccur determines the fact that we experience the flash and sound as occurring together in subjective time. Temporal experience mirrors the temporal temporal structure of brain processes without regard for when external events actually take place.
(2) Event time views claim that temporal binding is directed towards binding together external stimuli that occur at the same event time so that they are represented as occurring together in subjective time (See Arstila). If a sound occurs at the same time as a visual flash in event-time, then the flash and sound will be experienced as occurring together in subjective time. Temporal experience mirrors the temporal temporal structure of events in the external world without regard for when brain processes take place.
(3) Relative-time views claim that subjective time comes apart from both brain time and event time and is directed toward some third aspect. It might be that we experience two features as a single event only if it makes sense given our expectations and the behaviour we are engaged in that they would happen together (See Dennett & Kinsbourne).
Returning to Pepper and her ball, we might say that it is almost more magnificent that we experience Pepper as a cohesive bundle of dog-features chasing after a cohesive bundle of ball-features. If we disregarded our actual experience, and only looked at the temporal complexity of stimuli and information processing we might think it more likely that we should experience a chaotic blob of fur, black, dog-shapes, and barks chasing another blob of felt, yellow, ball-shapes, and bouncing sounds. Explaining why we experience the first sequence of events and not the latter requires a solution to the temporal binding problem.
Over the next couple of posts, we look at further issues of temporal binding and discuss the kind of explanation each of these views might propose to solve them.
Very interesting, appreciate the sources on different views of the phenomena.
Yes this is interesting.