Rescorla: Probability of Shock / Fear Conditioning

Question 1

CS-US Frequency vs CS-US Contingency

Answer 1

Contingency – notion suggests that conditioning only occurs when probabilities differ

When probability of US is higher during CS than at other times, excitatory condition occurs

When the probability is lower, inhibitory conditioning results

When probability of shock in the presence and absence of the CS is the same there is little or no suppression

Fixed probability of shock in the absence of CS increasing the probability of shock in its presence produced increasing suppression

Attention could be responsible for the less conditioning when US presented at higher probability in absence of CS

Question 2

Results

Answer 2

Independent of the overall probability of shock, there was little or no suppression if shock came with equal probability in the presence of absence of CS

With a fixed probability of shock during CS, increasing the probability in the absence of CS attenuated suppression

With a fixed probability of shock in the absence of CS, increasing the probability of shock in the presence of CS enhanced suppression

The notion that it is the number of simultaneous occurrence of the CS and the US that is important in condition

The total # of suppression not entirely accounted for in terms of either the total number of US events or the number of USs during CS

Disruptive effects upon condition of shocks occurring in the absence of CS:
Presenting US exclusively in the absence of CS led CS to be a conditioned inhibitor of the CR

Question 3

2 acquisition processes

Answer 3

1. Development of Pavlovian conditioned excitation as a result of CS and US occurring together
2. The development of Pavlovian conditioned inhibition as a result of the USs occurring in the absence of CS