Temporal forms of Classical Conditioning

Thus far, we have learned that in Classical Conditioning, the Neutral Stimulus always precedes the Unconditioned Stimulus, i.e., the bell rings first and then the food is presented. You might wonder if this is the only way conditioning can occur. After all, the bell is supposed to signal the arrival of the food, so it must precede it, how else will the association be effective? Well, not exactly. That’s where Backward Conditioning comes into the picture! While the NS preceding the US is the functional definition of Forward Conditioning, it is not the only type of Classical Conditioning. Let's explore these different types via our Burger King example.

It is a warm Saturday evening. You have just returned from the movies with your friends, Ross, Ted, and Sheldon, and you realize it's too late to go home and cook. You stroll down the street and find your happy place; Burger King! However, none of you are ready to part ways just yet. Looks like you’ll be dining in. After placing your order, the cashier informs you that their establishment is implementing three new ways to notify customers when their food is ready. He asks for your friends’ and your consent to try these, a request to which you all agree. He hands you three buzzers and instructs you to “wait for the buzz”. Since there were four of you but only three different methods, Ross is unfortunately left out. But you’re a great friend and you didn't want Ross to feel left out. So you cheerfully ask for a fourth, play buzzer. I hope all my friends will be as nice and considerate as you.

After about 10 minutes, the first buzzer goes off, alerting you that your food is ready. The food is brought to your table and after serving you, the buzzer is turned off. This is known as Delay Conditioning, a form of Forward Conditioning where the NS (the buzzing sound) not only precedes the US (the food) but also overlaps with it (the buzzer is turned off right after the food is served). If you recall Ivan Pavlov’s experiment with the dog, this is the kind of conditioning he described.

A few minutes later, the second buzzer chimes before being promptly silenced by the server. Ted is informed that his food will be out in 3 minutes and precisely 3 minutes later, the food is served. This is called Trace Conditioning, the second form of Forward Conditioning wherein the NS (the buzzer) is presented initially, followed by a short and fixed trace interval (the 3-minute wait) before the US is delivered. The primary goal of the trace interval is to serve as a memory retriever; the interval alerts you to the imminent arrival of your food.

The third buzzer sounds soon after, alerting Sheldon that his food is ready, but this time, the food arrives exactly as the buzzer goes off. This is Simultaneous Conditioning, a form of Classical Conditioning where the NS and the CS are presented simultaneously. In this method, the NS does not signal the arrival of the US as they are presented together; learning occurs as a product of associating the NS with the US as they are being presented together.

Finally, Ross gets his food. After having his sandwich served, the server wishes you all well and leaves the table. Suddenly, the server is reminded that he got Ross’s order wrong. He forgot to add the moist-maker to the sandwich! Fortunately for Ross, the fourth buzzer immediately sounds, alerting him to not eat his sandwich. The server comes over to apologise for the error, takes the sandwich away at once and replaces it with the correct order. This is known as Backward Conditioning, where the NS (buzzing sound) is presented after the US (the food). In this scenario, Ross is being treated with Inhibitory Conditioning; the NS (buzzer) signals the absence/unavailability of the US (food being taken away).

As everyone prepares to leave, the server arrives to ask for feedback on the methods employed. He wanted to know which method caused you to have the most anticipation and excitement for your food. Before anyone could answer, Ross chimed in and said that he certainly felt the least excited. This is precisely what you would expect from Backward Conditioning. Due to the US preceding the NS, the NS is unable to signal its arrival, which leads to the weakest form of associative learning. In fact, Backward Conditioning is more effective as a method of Inhibitory Conditioning. For Ross, it signalled the conclusion/absence of the US (his food was taken away), a form of Inhibitory Conditioning. Sure, backward conditioning can be used to signal the arrival of a US, but as the US precedes the NS, weaker associations are formed.

After Ross had shared his thoughts, the rest of the group offered their input. You mentioned that you perhaps felt the most excited about the food, which would be the likeliest outcome. In Delay Conditioning, the NS not only signals the arrival of the US but also leads into it due to the overlap of the NS, resulting in the strongest form of associative learning. Ted follows after, telling the server that he too was excited but was hoping that the wait time after the buzzer would have been slightly shorter, perhaps 1 minute would be terrific. Ted’s concern is valid as a longer Trace Interval can lead to a weaker association between the NS and US. Lastly, Sheldon mentioned that he felt little anticipation as the food was served simultaneously as the buzzer sounded. As the NS in Simultaneous Conditioning is presented simultaneously with the US, it does not predict the arrival of the US. In this case, it might be harder to learn that the NS signals the arrival of the US, leading to a weaker form of conditioning. 

Before leaving, Ross asked the server what he did to his sandwich to which the server sheepishly replied, “I had to throw it away…” At this, you and your friends had to drag Ross away before he had another meltdown over a sandwich!

References:

Domjan, M. P. (2018). Principles of learning and behavior. Cengage Learning.