Re: how does the human brain judge time?

   Matt, your question is an interesting one.  I have answered a question 
very much like it in the past but am happy to go over it again.  Our 
understanding of time and how we perceive it is not well understood.  The 
research that has been done can be divided into neurobiological and 
psychological.  The neurobiological studies focus on what areas of the 
brain are involved in "time sense".  The problem with identifying discreet 
brain structures as loci for time sense is that our brains process time at 
several levels.  There seems to be some agreement among investigators that 
events which occur in the range of seconds (and presumably longer) are 
processed separately from events which occur in the range of milliseconds. 
 Further, cognition (i.e. higher brain functions) is involved in the 
second-or-longer timing mechanism whereas it doesn't appear to have any 
affect on the millisecond timing mechanism.  The investigation of the role 
of cognition is the focus of most psychological studies involving time.  
   Most of the neurobiological research has focused on the first timing 
mechanism and two areas of the brain that have been implicated as being 
important in this sense of time are the basal ganglia and the cerebellum.  
The basal ganglia is a kind or receiving house for our sensory input, and 
our perception of time is more often than not based on sensory input.  For 
example, we experience the passage of time because we perceive one stimuli 
followed by another, followed by another, be they visual, auditory, 
tactile, or whatever.  In addition, both the basal ganglia and the 
cerebellum are involved in movement.  Movement is the basic response to 
perceived stimuli, and, if you think about it, has a very precise temporal 
component to it.  For example, if we see an object that we want to grab, we 
do not close our fist before our hand reaches the object.  But there are 
other areas of the brain involved as well.  Some studies have implicated 
the prefrontal right hemisphere and inferior parietal cortices, areas of 
the brain involved in higher-level cognition, as important "time sense" 
regions.  Indeed, experiments using pharmaceuticals such as 
anti-psychotics, psychedelics, and stimulants, which all affect higher 
level cognition, can also affect our sense of time.  Time sense is also 
affected in forms of dementia such as Alzheimer's disease and multi-infarct 
dementia, diseases that demonstrate pathological changes in these same 
cortical structures.  
   The psychological research deals with how we perceive time, and your 
experiment is a type of psychological experiment.  Most people have a 
decent ability to gauge time as it passes with some amount of precision.  
However, this ability depends greatly on other activities that the person 
is involved in, as your experiment will demonstrate.  Again, this is 
probably due to the increase in sensory input.  But activity does not only 
interfere with our sense of time.  Activity, especially activity that 
involves increased concentration will interfere with many of our senses.  
You may have noticed this if you or someone you were with were ever looking 
for a street address in an unknown area.  Invariable the person always asks 
for silence, as if unwanted sounds are disturbing his ability to see an 
address.  In the same way, playing disturbs our sense of time (as well as 
our mother's voice telling us its time for dinner).  Good luck on your 
project.