Delayed Reinforcement
Trace conditioning is defined by a temporal gap between conditioned-stimulus offset and unconditioned-stimulus onset.
Learning Across a Gap
Learning does not always require a conditioned stimulus to remain present until an unconditioned stimulus begins. In trace conditioning, the conditioned stimulus ends first, a temporal gap follows, and the unconditioned stimulus begins afterward. The central problem is therefore what remains from the earlier stimulus during the gap. Two related explanations are important: a stimulus trace can continue in the nervous system, and stimuli presented during the delay can acquire reinforcing value through association with a primary reinforcer.
The defining feature of trace conditioning is the gap between the end of the conditioned stimulus and the beginning of the unconditioned stimulus.
The Trace-Conditioning Timeline
Trace conditioning is defined by timing, not by the name of the particular stimulus. First, the conditioned stimulus is presented. It then ends, or reaches stimulus offset. A temporal gap follows. Only after that gap does the unconditioned stimulus begin. The conditioned stimulus is therefore no longer physically present when the unconditioned stimulus starts.
Identifying trace conditioning
A conditioned stimulus is presented and then ends. After a delay, an unconditioned stimulus begins. What feature makes this trace conditioning?
Locate the conditioned stimulus: The conditioned stimulus occurs first in the sequence.
Locate stimulus offset: The conditioned stimulus ends before the unconditioned stimulus begins.
Inspect the interval: A temporal gap separates conditioned-stimulus offset from unconditioned-stimulus onset.
Classify the arrangement: Because the conditioned stimulus ends before the unconditioned stimulus begins, the arrangement is trace conditioning.
The defining feature is the temporal gap between conditioned-stimulus offset and unconditioned-stimulus onset.
What Persists After Offset
A stimulus trace is the nervous-system trace that a stimulus leaves after the stimulus itself has ended. The physical conditioned stimulus is absent during the gap, but the trace provides a way for the earlier event to continue influencing learning until the later unconditioned stimulus occurs. Pavlov proposed this continuing trace as a basis for understanding trace conditioning.
Delay-Period Stimuli
A delay can contain stimuli in addition to the trace of the original conditioned stimulus. When a stimulus occurs during the delay and is associated with a later primary reinforcer, that delay-period stimulus can acquire reinforcing value. This acquired value is called secondary reinforcement. In this account, the delay stimulus is not merely a trace of the original conditioned stimulus; it is a stimulus that gains value through its association with the primary reinforcer.
Two possible contributors during one delay
A conditioned stimulus ends, a delay follows, and an unconditioned stimulus then begins. During the delay, another stimulus is presented. How can both the trace and the delay stimulus matter?
Track the original stimulus: After the conditioned stimulus ends, a stimulus trace may preserve its influence in the nervous system.
Track the added delay stimulus: The stimulus presented during the delay is a separate event occurring between conditioned-stimulus offset and unconditioned-stimulus onset.
Track the later reinforcer: The later unconditioned stimulus can provide the primary reinforcer with which the delay stimulus becomes associated.
Separate the mechanisms: The trace accounts for persistence of the original stimulus after offset, while secondary reinforcement accounts for reinforcing value acquired by a stimulus through association with a primary reinforcer.
Stimulus traces and secondary reinforcement can contribute to learning across the same delay, but they describe different sources of influence.
Trace Versus Secondary Reinforcement
| Feature | Stimulus trace | Secondary reinforcement |
|---|---|---|
| What it describes | A continuing nervous-system trace after a stimulus has ended | Reinforcing value acquired by a delay-period stimulus |
| What it originates from | The earlier stimulus | Association with a primary reinforcer |
| Where it matters | Across the gap after conditioned-stimulus offset | When a stimulus occurs during the delay and becomes associated with the later primary reinforcer |
| Relationship to the other account | Distinct from secondary reinforcement | Distinct from the stimulus trace |
The two mechanisms should not be collapsed into one. A stimulus trace explains how the earlier conditioned stimulus can continue to influence learning after its physical presentation has ended. Secondary reinforcement explains how a stimulus occurring during the delay can gain reinforcing value through association with a primary reinforcer. They are distinct accounts, yet both can help explain learning across delays.
Common Reasoning Errors
Treating trace conditioning as if the conditioned stimulus remains present until the unconditioned stimulus begins.
The gap between conditioned-stimulus offset and unconditioned-stimulus onset is the defining feature of trace conditioning.
Fix:
Identify the offset of the conditioned stimulus first, then check whether the unconditioned stimulus begins after a gap.Calling the stimulus trace the original physical stimulus.
A stimulus trace is a continuing nervous-system trace after the stimulus has ended.
Fix:
Describe the original stimulus as ended and the trace as what may preserve its influence.Using stimulus trace and secondary reinforcement as synonyms.
Secondary reinforcement concerns reinforcing value acquired by a delay-period stimulus through association with a primary reinforcer.
Fix:
Ask whether the explanation concerns persistence of the earlier stimulus or acquired value of a stimulus occurring during the delay.Assuming that any delay-period stimulus automatically becomes a secondary reinforcer.
The source describes secondary reinforcement as arising through association with a primary reinforcer.
Fix:
State that a delay-period stimulus can acquire reinforcing value through that association.
Check Your Understanding
A conditioned stimulus ends. There is a temporal gap. The unconditioned stimulus then begins. During the gap, a separate stimulus is presented. Explain which part of the arrangement illustrates trace conditioning, how a stimulus trace could support learning, and how the separate delay stimulus could contribute to secondary reinforcement.
Hints
- Start with the timing of conditioned-stimulus offset and unconditioned-stimulus onset.
- Use stimulus trace for the continuing nervous-system trace of the earlier stimulus.
- Use secondary reinforcement for reinforcing value acquired by the separate delay stimulus through association with the primary reinforcer.
A strong answer should distinguish the persistence of the earlier stimulus from the acquired reinforcing value of a stimulus presented during the delay.
Key Takeaways
- Trace conditioning contains a temporal gap between conditioned-stimulus offset and unconditioned-stimulus onset.
- A stimulus trace is a continuing nervous-system trace that can preserve the influence of a stimulus after that stimulus has ended.
- A stimulus presented during the delay can acquire reinforcing value through association with a primary reinforcer; this is secondary reinforcement.
- Stimulus traces and secondary reinforcement are distinct but complementary explanations for learning across delays.
- To analyze delayed reinforcement, separate what persists from the earlier stimulus from what new delay-period stimuli may acquire through association.
Key Takeaways
- Trace conditioning is identified by the gap between conditioned-stimulus offset and unconditioned-stimulus onset.
- A stimulus trace can support learning after the original stimulus has ended by preserving a nervous-system trace.
- Stimuli occurring during the delay can acquire reinforcing value through association with a primary reinforcer.
- Stimulus traces explain persistence of the earlier stimulus, whereas secondary reinforcement explains acquired value in a delay-period stimulus.