Hello. So folks in psychology of learning I thought
I’d make a brief video to talk a little about overshadowing versus blocking In classical
conditioning this is chapter 7 so remember in the phenomenon of overshadowing you start
presenting a compound stimulus that's two stimuli being presented simultaneously before
the unconditioned stimulus right so overshadowing starts with a compound stimulus being presented
two stimuli being presented simultaneously the thing is one of those two stimuli is more
Salient or stronger than the other stimulus and it is that more Salient or stronger stimulus
that is going to become classically conditioned the weaker of the two stimuli will not be
classically conditioned so we explained this or one possible explanation for overshadowing
is the information value explanation for classical conditioning so if the conditioned stimulus
is providing useful information to the organism then classical conditioning will happen you
have one weak stimulus and one strong stimulus both being presented simultaneously before
the unconditioned stimulus but one of those is stronger right and so the stronger stimulus
is providing the argument goes more useful information to the organism and so it is that
stronger stimulus that becomes classically conditioned in overshadowing that is overshadowing
next we have the phenomenon of blocking in blocking In classical conditioning remember
that one stimulus one neutral stimulus by itself is paired with the unconditioned stimulus
first so you pair that neutral stimulus with the unconditioned stimulus for a while then
you add a second neutral stimulus to the first creating a compound stimulus you present both
those stimuli simultaneously now for a while before the unconditioned stimulus then you
test those two what were neutral stimuli individually which one becomes classically conditioned
it is the first neutral stimulus that was paired by itself with the unconditioned stimulus
that becomes conditioned right the one that you add later on does not become conditioned
and remember we got competing explanations for the phenomenon of blocking so once again
you have the information value of the conditioned stimulus or information value explanation
for it the first stimulus was paired with the unconditioned stimulus first so it is
already providing useful information to the organism by the time you add a second stimulus
to that situation that second stimulus provides no new information and so is not conditioned
correct a second possible explanation for the phenomenon of blocking came from Rescorla-Wagner
theory where we said Rescorla-Wagner the amount of learning possible in any learning situation
represented by the Greek letter theory proposes that there is a maximum amount of learning
possible in any learning situation represented by the Greek letter Lambda and so when you
present the first stimulus with the unconditioned stimulus what happens is that first stimulus
uses up all of that Lambda or possible learning that can happen so by the time you add the
second stimulus to the situation in blocking all the learning has been used up and no more
learning can happen so those are two of the explanations for blocking remember there are
four total