COGNITIVE TASK SELECTION
Let’s assume we are looking around for a cognitive task to include in a new experiment. We want the task to have a number of well-defined characteristics. Some important features are:
- Results in a fairly wide range of performance (not just success and failure)
- Not be easily susceptible to learning (we may have to repeatedly give it to the same individuals)
- Not be something that some individuals have already learned before we test them
- Not rely on a gimmick that once learned becomes trivially easy
- Have good face validity (we want our individuals to try their best to succeed)
Many researchers decide to include measures of cognitive workload in their studies after they already have a defined task/event/activity that they want to examine. Usually, it is a complex task such as driving in a simulator or reading medical X-rays. Before incorporating a metric such as the Index of Cognitive Activity into their research designs, these researchers wish to test it first on a ‘simple case’ to be sure they understand how it works. It is here that they get into trouble, because they do not select this test case wisely. We often get calls from researchers who have tried to use the simplest of neurological tests. Unfortunately, very simple tasks do not elicit very much cognitive workload. The brain just does not have to work very hard to recognize the letter ‘A’. The result of “simple” task selection is that the researchers are disappointed and conclude that physiological workload measures are not reliable, and they turn to other ways of measuring cognitive workload such as self-report scales. In fact, the Index of Cognitive Activity would probably have worked very well in their complex environments. We discourage researchers from trying to work with much too simple a testbed.
So what types of tasks would be effective? One guideline we can offer from our own research using the ICA is that problem solving usually produces a nice range of both performance outcomes and cognitive workload. Even simple problem solving such as giving the individual verbal arithmetic problems to solve will often be sufficient.
A second guideline is that any activity that involves multi-tasking works well to elicit cognitive workload together with a range of performance outcomes. For instance, one might ask individuals to search a visual display while at the same time recognizing one specific sound in a series of auditory tones. Any complex activity that requires shifting attention from one task to another will usually generate reliable cognitive workload.
We can also mention several types of tasks that probably will not work well:
- Simple ‘look-up’ memory tasks – such as who was President of the United States in 1960; what is the capital of California; how old were you when you first went to a concert
WHY: there is little mental effort involved in these tasks—the individual either knows or doesn’t know the answer. Simple retrieval from long term memory does not typically activate very much in the brain.
- Simple perceptual tasks – such as find the single letter G in an image containing many instances of the letter C.
WHY: these are excellent tests for perception, but they require little thinking. These are simple pattern recognition tests.
- Simple working memory tasks – such as n-back or digit span.
WHY: these are excellent tests of working memory capacity but do not recruit many other brain processes.
Note that all of these caveats involve simple tasks. Such tasks typically are memory tasks of one sort or another and were designed to isolate and study just the memory function needed for the task. Measurable and reliable mental effort most often requires multiple cognitive processes or functions.