Wednesday, October 9, 2013


Did you catch that article in the Economist on critical flicker-fusion frequency and the perception of time?
Well, it was a good one.

You know, CFF is sorta the processor speed our brains have when dealing with visual stimuli.  Our rate is different than most animals, and scientists have been sussing on how that relates to our perception of time...

Or rather if having a high CFF would make it seem that the world around you was moving in slow motion.

I may be extrapolating that the slow-mo effect would then change the perception of time, though I presume most animals are less interested in the concept of time than humans.  Perhaps layering my own perspective on top of how another species perceives the world around them, to attempt to understand how the varied input factors would change one's base interaction with the space around them.

Which is pretty fascinating.

Here is a link to the full paper, if you want to read more than the magazine clipping below.  I, for one, prefer to read the source materials that generate these bite sized news bits.

(I have included this picture of a golden mantled ground squirrel for those who hate reading science stuff.)

For people, the average CFF is 60 hertz (ie, 60 times a second). This is why the refresh-rate on a television screen is usually set at that value. Dogs have a CFF of 80Hz, which is probably why they do not seem to like watching television. To a dog a TV programme looks like a series of rapidly changing stills. 
Having the highest possible CFF would carry biological advantages, because it would allow faster reaction to threats and opportunities. Flies, which have a CFF of 250Hz, are notoriously difficult to swat. A rolled up newspaper that seems to a human to be moving rapidly appears to them to be travelling through treacle. 
Mr Healy reasoned that the main constraints on an animal’s CFF are its size and its metabolic rate. Being small means signals have less far to travel in the brain. A high metabolic rate means more energy is available to process them. A literature search, however, showed that no one had previously looked into the question. 
Fortunately for Mr Healy, this search also showed that plenty of people had looked at CFF in lots of species for other reasons. Similarly, many other people had looked at the metabolic rates of many of the same species. And size data for species are ubiquitous. All he had to do, therefore, was correlate and repurpose these results. Which he did. 
To simplify matters he looked only at vertebrates—34 species of them. At the bottom end of the scale was the European eel, with a CFF of 14Hz. It was closely followed by the leatherback turtle, at 15Hz. Tuataras clocked in at 46Hz. Hammerhead sharks tied with humans, at 60Hz, and yellowfin tuna tied with dogs at 80Hz. The top spot was occupied by the golden-mantled ground squirrel, at 120Hz. And when Mr Healy plotted his accumulated CFF data against both size and metabolic rate (which are not, it must be admitted, independent variables, as small animals tend to have higher metabolic rates than large ones), he found exactly the correlations he had predicted.
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