does bridging drop impedance

a little back ground on my question, i made a bet with a salesman at my job that bridging a two channel amplafier into one channel would cause the amplafier to *see* half the ohm's actually connected to it (ie. 4 ohm load = 2 ohm load) any how this was told to me many many years ago when i was just starting to install and thru out the years when mentioned none ever opposed to that theory.  untill now, a salesman at my job disagrees with it and in turn says it makes no difference if an amp is bridged or not that the amp *sees* waht ever ohm's the speakers are at (ie 4 ohm's = 4 ohm's).    the reason i ask here is because when trying to make my point it became painfully obious to me that my knowledge on the theory was here say. so knowing that there are plenty of guys on these forums that konw amplafier internal workings far better than myself i decided to post my newby question.    does bridging cause the amplafier to *see* a lower ohm load than that of the speaker.  

ps. i really hope im right on this one,  coz it's gonna hurt to have to buy this mustard salesman lunch 

thanks for the technical answer bro,  it's waht i was looking for.   just to make sure im understanding it right,  the amplafier does work twice as hard when bridged but it does not actually see less ohm's so when i was told the amplafier sees a greater load it was right but the ohm's thing was not?   again thanks much for the reply.   

ferretvw is correct.  No matter what someone may do or not do to an amplifier it will not change the impedance of the speaker.  4-ohms is 4-ohms.

haemphyst is correct.  Placing a load across two bridged amplifier channels will cause each channel to operate at the same level as the equivalent of 1/2 the total load.

davngr, the amplifier does not "see" anything.  It is an electrical device.  Bridging a 2-channel amplifier with 4-ohms total is the same as loading each amplifier channel with 2-ohms.  I think you and your pal should buy each other lunch.