1. Cognitive Processes PSY 334
Chapter 6 – Human Memory: Encoding and Storage
May 7, 2003

2. Activation Activation – how available information is to memory:
Probability of access – how likely you are to remember something.
Rate of access – how fast something can be remembered.
From moment to moment, items differ in their degree of activation in memory.

3. Factors Affecting Activation
How recently we have used the memory:
Loftus – manipulated amount of delay
1.53 sec first time, then 1.21, 1.28, and 1.33 with 3 items intervening.
How much we have practiced the memory – how frequently it is used.
Anderson’s study (sailor is in the park)

4. Spreading Activation
Activation spreads along the paths of a propositional network:
Dog – c Gambler – c
Bone – m bone – m
1.41 sec 1.53 sec
Associative priming – involuntary spread of activation to associated items in memory.

5. Associative Priming
Meyer & Schvaneveldt – spreading activation affects how fast words are read.
Subjects judged whether pairs of related & unrelated items were words.
Ratcliff & McKoon – priming influences word recognition.
Subjects identified words from sentences faster with priming.

6. Practice and Strength
Amount of spreading activation depends on the strength of a memory.
Memory strength increases with practice.
Greater memory strength increases the likelihood of recall.

7. Power Function
Each time we use a memory trace, it gradually becomes a little stronger.
Power law of learning:
T = 1.40 P-0.24
T is recognition time, P is days of practice.
Linear when plotted on log-log scale.

8. Long Term Potentiation (LTP)
Neural changes may occur with practice:
Long-term potentiation (LTP) in hippocampus.
Repeated electrical stimulation of neurons leads to increased sensitivity.
LTP changes are a power function.