[b]i've experienced this
scenario several times that when i yawn, then next person/people close to me at that particular time will start yawning simultaneously and vice versa, i have always wondered and i have done my researcher but still not satisfied

below are the few explanation i could gather and thought i should share

Most people, when they see
someone else yawn, quickly feel
the urge to yawn as well.
Between 40 and 60% of people
automatically find yawning
contagious and yawn
themselves. The standard
answers from scientists as to
why people find yawning
contagious used to be that,
although it was clearly a real
phenomena, there was no
obvious reason for it. Research
conducted in 2005 by Finnish
scientists, however, may point
to certain parts of the brain as
being responsible.
When a person witnesses
someone else yawning, he or
she has a mostly unconscious
urge to do the same. People
may become conscious of the
urge, but scientists suggest the
beginning of the yearn to yawn
is unconscious. This means that
the signal must bypass the
mirror neuron system, which is
a process that would make this
response a conscious and
imitative act. Scientists have
often, in the past, suggested
that the mirror neuron system
causes yawning.
Instead, researchers found that
seeing someone else yawn
seems to render the
periamygdala sections of the
brain inactive. This is a tiny part
of the brain on either side of
the head that helps interpret
things like facial expressions. If
it was working, the conscious
response to yawning might be,
“Oh, he’s tired.” By temporarily
blocking such a reading,
however, the response cannot
at first be a conscious
perception.
This does not explain
specifically why people find
yawing contagious, but it does
suggest that there are brain
sections responsible for a
person’s perception of a yawn.
In addition, the response does
not begin with the mirror
neuron system but instead
bypasses it.
Other explanations include the
idea that yawning may have
evolved in early man as a way to
signal or set up sleep schedules.
A contagious yawn meant that
perhaps more than one person
was tired and people should
sleep accordingly. Since
tiredness might indicate a less
energetic response to danger,
yawning would mean people
should find shelter and get out
of danger. Those who yawned
and paid attention to it may
have been selected into the
species because they got
proper sleep and were more
alert to danger.[/b]