Classical Conditioning Variables

The temporal relationship between the conditioned stimulus (CS) and the unconditioned stimulus (US) is crucial.
Random presentations of the CS and US do not lead to conditioning.
Some form of pairing between the CS and US is necessary.

Short Delay Conditioning:
- The CS starts just before the US presentation.
- They usually overlap to some extent.
Long Delay Conditioning:
- There is a longer gap between the onset of the CS and the onset of the US.
- The CS is delayed until the US presentation begins.
Trace Conditioning:
- The CS is presented prior to the US, with a gap between them.
- The offset of the CS occurs before the onset of the US.
- Requires maintaining a memory trace of the CS during the US presentation.
Simultaneous Conditioning:
- The CS and US are presented at the same time.
Backward Conditioning:
- The US is presented before the CS.

Conditioning is most effective when the CS precedes the US.
Short delay, long delay, and trace conditioning arrangements show good evidence of learning.
Simultaneous presentation or backward arrangements rarely show excitatory conditioning.

The interval between the onset of the CS and the onset of the US is the interstimulus interval (ISI).
Conditioning works best when the CS occurs slightly before the US.
Optimal interval varies depending on the type of learning procedure:
- Eye blink conditioning (humans): ~0.5 seconds between tone (CS) and air puff (US).
- Taste aversion learning: 1-2 hours between taste/flavor (CS) and sickness (US).
- Fear conditioning: seconds to minutes interval.
ISIs shorter or longer than the optimal ISI result in poor conditioning.
Delay conditioning is generally better than trace conditioning when the interval is constant.

Conditioning can occur even without a discrete CS.
Repeated US presentations at a constant rate lead to temporal conditioning.
The passage of time since the previous US acts as the CS.
Example: Hunger response influenced by the time of day (e.g., feeling hungry before a regular morning tea break).

Salience refers to the degree to which a neutral stimulus is noticed or attended to, influencing how quickly a conditioned response to it is learned.
The intensity of the stimulus is an aspect of salience.
Example: Mustard has a high salience, while hot dog buns have low salience.
- More likely to develop taste aversion to mustard than hot dog buns after getting sick.
- Learning about less salient stimuli takes longer.

When two conditioned stimuli are presented together, it's known as a compound stimulus (e.g., hot dog with mustard).
If a compound stimulus is followed by a US (e.g., getting sick), the more salient stimulus is learned about, while the less salient stimulus is overshadowed.
Following sickness after eating a hot dog with mustard, a taste aversion to mustard is more likely to develop than to the hot dog bun.

Learning about the salient stimulus overshadows learning about other stimuli present.

The intensity of the US and the size of the resulting unconditioned response affect the amount and rate of learning.
Example: Being bitten by a dog leads to a more profound fear of dogs than only being barked at.
A very traumatic experience can produce a lifelong fear.
Repeated exposures to a less intense US are needed to produce the same level of fear.

Generally, multiple CS-US pairings are needed for learning to emerge.
Taste aversion learning is an exception that can occur with a single trial.
Additional CS-US pairings increase the strength of the learned response.
Example: A child learning to fear a neighbor's house after multiple encounters with an angry dog.

Graphically, learning follows a decelerating curve.
Initial CS-US pairings have the largest impact on behavior.
The slope of the curve is steep at the beginning but flattens with continued pairings.
Approaches a maximal or asymptotic value.
From a survival standpoint, it's crucial to learn quickly about stimuli that predict important biological events.
Failure to learn quickly can result in severe survival disadvantages.

If the CS is presented repeatedly without the US, the conditioned response diminishes and eventually disappears.
This phenomenon is known as extinction.
Example: A phobic response to dogs subsiding after having positive experiences with a docile labradoodle.

Similar to the learning curve, the initial CS alone trials are most effective in changing behavior.
Conditioned responses may continue to occur at a low frequency even after many CS alone trials.
Continued extinction trials can eventually eliminate the conditioned response.

Extinction is often temporary, and the original learning can be restored in various ways.