Wednesday 23 April 2008

The PHI Experiment

Those of you who have read my book will know that I make great play upon a phenomenon known as the PHI Effect.

In 1910 Czech psychologist Max Wertheimer noted that two lights flashed through small apertures in a darkened room at short intervals would appear to be one light in motion; this perception of movement in a stationary object he termed ‘the PHI phenomenon’ and this in turn became the basis of a whole school of psychology, Gestalt. Together with two assistants, Wolfgang K√∂hler and Kurt Koffka, he began to study the PHI phenomenon in earnest. Although they spent many years looking into the subject it was to become something of an oddity within human perception. That did not mean that the phenomenon did not continue to intrigue and beguile all that encountered it.

In 1977, the philosopher Nelson Goodman asked psychologists Paul Kolers and Michael von Grunau what would happen if, in the PHI phenomenon, the two illuminated spots were of different colours. This was so simple but revolutionary that the two psychologists immediately set up an experiment. They had a good idea of what to expect; either that two flashing spots would replace the single spot, or an illusory spot would change from one colour to another working its way through all the hues between. What actually happened was astounding. Two different coloured spots were illuminated for 150 milliseconds each (with a 50-millisecond interval); the first spot seemed to begin moving and then change colour abruptly in the middle of its illusory passage toward the second location. Goodman wondered:

How are we able to fill in the spot at the intervening place-times along a path running from the first and second flash before the second flash occurs?

For Daniel Dennett the mind somehow holds back the full perception of this experience until it is fully understood. The colour change is experienced by consciousness after the exercise has been completed. Dennett says:

Suppose the first spot is red and the second, displaced, spot is green. Unless there is ‘precognition’ in the brain (an extravagant hypothesis we will postpone indefinitely), the illusory content, red switching to-green-in-midcourse cannot be created until after some identification of the second, green spot occurs in the brain. But if the second spot is already ‘in conscious experience’ would it not be too late to interpose the illusory content between the conscious experience of the red spot and the conscious experience of the green spot? How does the brain accommodate this sleight of hand?

I suggest that this proof that the brain 'buffers', and therefore by implication, 'records' sensory information before it is presented to consciousness. In this way I believe that I show how it can be that at the point of death a full recording of ones life can be re-shown as the 'Panoramic Life Review' as it is termed by NDE researchers.

On-line is a fascinating example of how the PHI phenomenon actually works. Follow this link and check it out:

Let me know what you think.


Hurlyburly said...

I'm comprehending this about 90% Unfortunately i can't seem to open up that link at work but i will do when i get home. If i read it a few more times and research it a bit i'm sure i'll be with you in no time!

Amazing how such a simple suggestion can shed a who new perspective on something.

johar said...

Are the coloured spots being flashed at the same time but we see them one after the other? Not sure I understand? I get that the brain receives info and makes sense of it before it is presented to us consciously so how does this experiment show this to be true?

Karl Le Marcs said...


I knew you were aware of the PHI Effect (PHInomenon? Ha!) but I wonder if you are aware of Magni-PHI (not my gag this time!), it is an enhanced version of Wertheimer's and whilst it does require some prior PHI knowledge, it is well worth looking into.

Here is a link:


ra from ca said...


I am aware through my study of colour that if you stare at any colour and look away or look at grey you will see its complement; e.g. stare at red you will see green, stare at blue you will see orange, stare at violet you will see yellow. Did this experiment take that into account? Rather than precognition or brain buffer it could just be the phenomenon known as "simultaneous contrast"