300 million years of pre-crastination

I meant to write this post last night but then something came up. I had some time set aside this morning, too, but email chewed that up. We all procrastinate, even if only occasionally.

In actual fact, I didn’t procrastinate writing this post at all: I thought I was going to work on it tonight, but it turns out I have an hour in between commitments at a student conference and so I am working on it sooner than I thought. I am pre-crastinating.

Pre-crastination is “the tendency to begin or to finish tasks as soon as possible,” as explained by Ed Wasserman and Stephen Brzykcy in an article that just appeared in the Psychonomic Bulletin & Review. The article reports an experiment investigating whether pigeons—like humans in an earlier study—also exhibit a tendency to pre-crastinate.

Why were Wasserman and Brzykcy interested in pigeons? As Ed explained it, “the evolutionary lines leading to humans and pigeons diverged some 300 million years ago! What might behavioral commonalities mean given such discrepant lineage? Clearly, the mechanisms of reward and choice are very old indeed.”

To test those 300-million years old mechanisms, Wasserman and Brzykcy put their subjects into a conditioning chamber in front of—what else—a touch screen. The pigeons could obtain food by learning to peck the touch screen three times: a first peck into a square in the center of the screen, a third and final peck onto a star symbol that randomly appeared on the left or right side of the screen and that was immediately followed by food reward, and a second intervening peck that measured the behavior of interest.

On those critical second pecks, pigeons were given a choice between two locations on the screen: The center position that was the target for the first peck, and the side position that would later contain the star (and hence trigger a reward) for the third peck. The choice of position was of no consequence to the pigeon’s future reward, and hence there was no economic incentive for the pigeon to peck one way or the other.

Which of those two squares would the pigeons choose?

Wasserman and Brzykcy reasoned that three possible outcomes might be observed: The pigeons might persist with the center location from the first peck (procrastination); they might randomly peck one or the other location (indifference); or they might switch from the center to the side location in anticipation of the final, rewarded step (pre-crastination).

The results overwhelmingly pointed to the final possibility: Within a short time (in pigeon terms) all subjects pre-crastinated nearly 100% of the time. Far from being random, when making the second (choice) peck, the pigeons anticipated where the final peck to the star would be rewarded, eagerly switching to that position even though doing so was of no consequence to their economic welfare.

Why did the pigeons pre-crastinate?

When human participants were asked in a related study why they pre-crastinated, they frequently expressed the desire to finish the assigned tasks as quickly as possible. It appears that pre-crastination satisfies our urge to move closer to a goal by completing some subgoal sooner than necessary. Doing so may reduce the load on our “prospective” memories; that is, memory to perform a planned action at the appropriate time in the future.

Wasserman and Brzykcy argue that there is plenty of evidence to suggest that even pigeons are capable of prospective memory. It follows that they, too, may have been eager to lighten the load on their memory by switching the position of their pecks sooner rather than later.

This possibility appears quite attractive: Under a procrastination (or random) scenario, the pigeon must remember to switch the location for its final peck for a longer time than if the pigeon pre-crastinates and switches immediately after its first mandatory peck in the center.

Other interpretations of pre-crastination stress familiar concepts from the realm of associative learning: conditioned reinforcement arising from the early choice response being more promptly followed by the food-paired star stimulus, and sign-tracking arising from the attraction of organisms to stimuli and locations that reliably signal reward.

Regardless of which interpretation ultimately proves best, Wasserman and Brzykcy suggest that it is “…precisely because pre-crastination does not appear to support the economic interests of the individual organism that makes it such an interesting and challenging behavioral phenomenon for psychological science.”

Pre-crastination may thus represent a behavioural disposition that we share with pigeons and that may be even older than 300 million years.

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