Expectancies add to the perceptual process and enable us to breach the 7 bit limit on decoding.
Hence, expectancies short circuit that 7 bit limit of information we have to deal with in the short term memory process.
If you glance into my classroom from the hallway for less than a half of a second, you could write a ten page essay on what you saw.
You could describe how the people were arranged; what they were wearing, what they were doing, how the room was designed and what it is used for; what the person in the front of the room was doing…etc. etc. etc.
You can do all this because your expectancies (your experience) add to the process of reconstructing the percept.
Of course, just as something is gained, something is lost. Our expectances can be so powerful as to re-construct a percept and give us an experience that is not really there—that does not exist in reality.
There will be some examples on the following pages that will demonstrate this.