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Pupil Dilation Response

We respond to sudden changes in our environment (loud sound, flash of light) by turning to look at the source of the disturbance: this physical orientation toward the stimulus is accompanied by a many changes within our body. The heart rate and respiration rate slow down, skin conductance decreases, there is a burst of brain activity, and our pupils dilate.

The physical movements to 'orient' towards the sound or light flash, accompanied by the internal physiological changes, are called the Orienting Response (OR), and was first described by Pavlov. The Orienting Response quickly habituates if the stimulus is repeated: this allows us to be continually aware of 'new' changes in our sorroundings.

The pupil dilation response (PDR) is used in one of two ways: as a detection tool - to determine when sound levels rise to detection thresholds, and as a discrimination tool to probe differences between two louder sounds. In the detection task, we monitor the pupil diameter, and simultaneously ask subjects to give us an 'aye' or a 'nay' about whether or not they heard the sound. We can then compare the PDR responses to the voluntary responses by the subjects (usually recorded via a key-press), and can then determine how accurate the PDR is, compared to a more traditional method of assessing human performance.  Is the PDR more sensitive, or is it less sensitive? So far, it seems that the two methods are equally sensitive, but as they say, further investigation is underway.

Interestingly, a similar technique seems to underlie the fictional Voight-Kampff machine, used by Harrison Ford in the Noir Sci-Fi classic, Blade Runner. He uses a machine that tracks 'the contractions of the pupil' to distinguish humans from artificially created beings. Now if we could only apply a lie detector test on people over HDTV (read C-SPAN).....

We are currently gathering more comprehensive data, and if you want to volunteer and help us out, here's how.  You won't get rich in the process, but we do offer some minor compensation (along with the chance to help us learn more about ourselves)...

  • Our Illustrious Leader
  • The Takahashi Laboratory
  • Institute of Neuroscience
  • University of Oregon