Learning --- Aquisition
Memory --- storage and retrieval of information
Associative learning
is based on the relationship of one stimulus to another
Examples:
Classical conditioning (Pavlov)
bell ring --- food --- salivation
Operant conditioning (Thorndike)
trial-and-error learning
lever pressing (out of curiosity) ---> food.
Non-associative learning
Habituation --- decrease in behavior reflex response to repeated harmless stimulus
Imitation learning
Stages of memory
Iconic --- e.g. visual afterimages (1 sec)
Short-term working memory
small capacity (7 items plus/minus 1)
What is the possible mechanism?
Long-term memory
large capacity (some estimates 109 bits, relatively permanent).
| Physical basis of memory is in synaptic modification which alters the mapping of inputs to outputs. |
| The strength of the modification is determined by how often input and output activity occurs together, and by the strengths of the input and output activities. |
Hebb ("Organization of behavior", 1949) --- "When an axon of cell A is near enough to excite a cell B and repeatedly or persistently takes part in firing it, some growth process or metabolic change takes place in one or both cells, such that A's efficiency as one of the cells firing B, is increased"
A simple model
DWij = a figj
| Storage: Let {fn,gn} be a set of input/output activity pairs. |
Wn = Wn-1+gnfnT
| Recall: g = Wf |
| Perfect Recall, if {fn} are orthonormal, the
system shows perfect recall.
g = Wnfm = gm |
An example (training of association B->I, I->T, T->P, Mathematica code here)
| Interference effect. As the number of instances increases, the quality of recall decreases. |
| The recall is rather robust against noise. |
| Input needs not be complete to get correct output |