Logan:  Basic Principles of Learning

                         SELECTIVE ATTENTION

          An organism perceives only some of the stimuli in the 
         environment at any moment and furthermore, learning is
         largely restricted to stimuli that are perceived by the 
         organism as being important.

     Like so many other concepts in Psychology, we are all personally 
familiar with attention.  You have most probably been advised to give a 
teacher your "undivided attention," and have also probably had your 
attention distracted from an important assignment by an unusual or 
unexpected event.  It is not surprising that one of the factors that 
determines the attention-getting value (salience, perspicuity) of
a stimulus is its intensity.  The importance of attention for learning 
is that there may be little or no learning about stimulus events that 
are not noticed.
     
     Pavlov reported a relevant phenomenon in the context of classical
conditioning.  He used as an antecedent stimulus a compound of two 
stimuli such as a tone and a light with one being more intense than the 
other.  After pairing this compound S with food US to dogs, he tested 
with each of the stimuli presented separately.  Only the more intense 
of them elicited conditioned salivation, indicating that it had 
completely OVERSHADOWED the less intense element of the compound.  One
interpretation of overshadowing is that the organism normally only 
attends to one stimulus at a time; the more salient one commands the 
organism's attention and the weaker stimulus simply is not noticed.  
Pavlov also reported a related phenomenon called BLOCKING.  If one of 
two equally intense stimuli is first used as a CS alone, and then is 
combined with the second stimulus, all the while the US being given on 
every trial, the added stimulus fails to develop an association with the 
US.  The original S, having already been conditioned, apparently commands
the organism's attention so that the added stimulus is not really
noticed.  Blocking is like overshadowing except that the stimulus has
acquired its attention-getting value.

     We use the term SELECTIVE ATTENTION when the differential control 
of behavior among the available stimuli cannot readily be attributed to
differences in salience.  In addition to blocking, an experimental design
demonstrating selective attention is to present one stimulus (say, a
light) on every trial with 50% partial reinforcement.  This would be
perfectly adequate to produce conditioning were it the only stimulus
being used.  When, however, it is combined with other stimuli (say, two
tones) that are more informative about the occurrence of the US, the
organism apparently learns to pay attention only to the informative stimulus.

     Selective attention is not the same as receptor-orienting acts.  
The latter, as the name implies, means directing one's sensory receptors 
in such a way as to maximize a source of stimulation, such as when you 
look at some particular object in the environment.  Receptor-orienting 
acts are peripheral, involving overt turning of the head and eyes, 
touching an object, putting it to one's tongue, sniffing, and so forth.
Selective attention, in contrast, is presumed to be a more central, 
cognitive process.  Many psychologists of a behavioristic persuasion 
have shunned the notion of selective attention because it seems to imply 
a homunculus inside the mind scanning all of the sensory stimulation and
deciding what to attend to at any moment.  This image is something like 
the television director who sits before a number of TV monitors that show
the action from different angles and decides to put first this one and
then that one on the air.  The problem is that such an image begs the
important question of what rules govern the homunculus in deciding which
stimuli to bring into focus.
     
     Another reason for caution in applying the Principle of Selective 
Attention is that there is some evidence that learning may proceed quite
effectively without our being consciously aware (and hence paying 
attention) to the controlling events.  For example, classical
conditioning  has been reported with stimuli that are subliminal (below
the threshold intensity required for the person to be able to report
their occurrence).  Nevertheless, it is clear that the number and variety
of stimulus energies continually bombarding our senses greatly exceeds
the number to which we can attend at any moment in time.  The
quantitative limitation of our consciousness is sometimes referred to as
the CHANNEL CAPACITY, and the presumption is that the irrelevant,
redundant, and relatively insignificant information being received by our
senses is somehow filtered out, or at least attenuated (reduced) such
that the most important information becomes the focus of attention.  The
notion is that an organism only perceives a small part of the stimulation
that is received, that the amount that can be perceived at any instant is
limited, and that the organism can, at least to some extent, voluntarily
control what is perceived.  Attention may be commanded involuntarily by
intense and unusual events, but the organism can selectively attend to
less salient features of the environment.

     There is little question that people can selectively attend to 
particular aspects of the total stimulus environment.  If you press the
fingernail of one index finger into the palm of the other hand, you will 
most likely notice the minor pain as your fingernail digs into your palm.
However, without changing anything "outside," you can redirect your
attention to the pressure that you palm is applying against your finger
since those stimuli, while less perspicuous are equally present.  
Furthermore, selective attention is learnable.  You can, for example,
improve the skill with which you can attend to stimuli in your peripheral
vision; speed reading courses entail learning to take in a wider
perception of printed words.  Similarly, the study of art and music
appreciation involve learning to attend not only to the principal theme
of the work, but to less salient but no less interesting features of it.
One very important aspect of training in selective attention is learning
torecognize when attention is drifting toward a naturally more compelling
stimuli.  We have all missed parts of a lecture because our thoughts
wandered into appealing daydreams without our immediately realizing it.
The speaker's words continue to strike our ears, but getting the message
requires selective attention.

TERMS: Receptor-orienting act, selective attention, blocking,
overshadowing, compound stimulus