Are you good at multi-tasking? Are you sure?

I was intrigued by a recent paper Cognitive control in media multitaskers in the highly-regarded journal Proceedings of the National Academy of Sciences. The study looked at the information processing styles of self-reported media multitaskers, defined as users of two or more content streams simultaneously, compared with those who do not multitask in this way. (I will skirt over the irony both that I was supposed to be doing something else at the time I spotted the BBC report of the research, and that my son has just switched on the TV as I type this review on my laptop.)

An electronic copy of the paper was posted online in August 2009, ahead of publication in the print journal (doi: 10.1073/pnas.0903620106)

An electronic copy of the paper was posted online in August 2009, ahead of publication in the print journal (doi: 10.1073/pnas.0903620106)

In their research, Ophir et al asked 262 University students to complete an online self-assessment questionnaire regarding both the total number of hours spent using different media (they specified 12 formats including TV, online video use, music, print media, e-mail and text messaging) and how likely they might be to use some of these concurrently alongside a primary task. The authors then generated a numerical Media Multitasking Index (MMI) and ranked the students. Those with a score one or more standard deviations below the mean (light media multitaskers, LMMs) or one or more SDs above the mean (heavy media multitaskers, HMMs) were then invited to participate in a series of cognitive ability tests. In total there were between 30 and 41 students taking the various tests, evenly split between LMMs and HMMs.

Central to the whole study was the issue of working memory, a concept we have discussed previously on JLB. Some of the experiments were designed to look at the students abilities to filter out distractions and remain focused on the main task. In one test, for example, the students were asked to compare the orientation of two red rectangles in consecutive images shown to them 900 milliseconds apart. To investigate the influence of distractions, the image also included 0, 2, 4 or 6 blue rectangles. Each student was asked to do this 200 times in one sitting,  during which there were an equal number of slides in which the position changed and in which it did not (the order in which they saw each of the image pairs was randomised). This test revealed a difference between the LMMs and the HMMs. Contrary to the hopes of self-confessed media multitaskers everywhere, the HMM group seemed to be more easily distracted than the LMM, whose performance was largely unaffected by the presence of blue rectangles.

In a second test, the investigators looked into the ability of participants to hit the correct button “animal” v “nonanimal” when presented with 24 words. Each word was presented one at a time, and all 24 words were used twice in the sequence (ie 48 words total). The variation was then introduced whereby the students were presented with the same words again, but this time with the additional instruction that they should refrain from hitting the button if they heard a stop tone before they responded. The signal was transmitted 225 ms before the mean response time, and was used on 25% of occasions. In this test there was not a significant difference between the two groups.

There was also no significant difference between the HMMs and LMMs in the first part of a third test. Participants were shown a sequence of letter pairs 300 ms apart (the letters were red on a black background, the relevance of this will be reached in a moment). The students were to hit the “no” button on all occasions except when there was a cue “A” followed by a probe “X”, hence this is known as an AX Continuous Performance Task (AX-CPT).

A difference was reported, however, when distractors were introduced into the AX-CPT. Between the cue letter (red on black, remember) and the probe letter (also red on black), the participants were presented with three distractor letters which were white on black. The distractors were never A, X or indeed K or Y both of which were entirely omitted from the study to avoid shape recognition clashes of X v Y/K. The overall time between cue and probe was held constant (4900 ms) relative to original AX-CPT test.

In the AX-CPT test with distractors, the HMM students were found to have the same accuracy as the LMM cohort, but responded more slowly. Alongside the relative responses in the rectangle distraction test, it seems that HMMs are worse than LMMs at filtering out irrelevant environmental stimuli.

Given the inherent need to swap between activities implicit in multi-tasking, the findings from the task-switching test are probably the most illuminating. In this experiment, the students were presented with a cue that said either “letter” or “number” followed by a stimulus that always featured one letter and one number. If the “letter” cue had been shown, the participants were to ignore the number and press the left button for a vowel and the right button for a non-vowel (only 4 consonants (K, N, P, S)  and 4 vowels (A, E, I, U) were ever used to avoid bias to the non-vowel side; O was not included). conversely if the “number” cue was used then it was left button for “odd” and right button for “even” (again, only 4 of each sort of stimuli were shown; the numbers 1 and 0 were omitted. Each student saw 4 sets of 80 cue and stimulus pairs, 40% involved task switching and 60% non-switching. They were given “warm-up” activities either involving switching between numbers and letters or non-switching.  HMMs were slower to respond than LMMs in both non-switch (259 ms) and switch (426 ms) trials. This result is interpreted as showing that HMMs are less effective at suppressing irrelevant tasks.

In the final set of studies, the researchers looked at abilities to ignore distractions within memory. This was investigated by conducting so-called “two-back” and “three-back” tasks in which participants were asked to indicate whether a letter on the screen was a “target”, i.e. the same as the letter 2 or 3 previously (in respective study) or “non-target”, i.e. different. Each student has 3 x 30 goes, in which 10 were targets and 20 non-targets.

In the two/three-back tasks the HMMs again performed less well than the LMMs. Unsurprisingly, both groups were worse in the three-back tests than in the two-back tests and their relative declines between the two were similar. Interestingly, however, HMMs had a greater tendancy to identify false positives, i.e. to report a non-target as target, particularly in association with letters than had come earlier in the sequence and were thus “familiar” but not in the correct relative position. This effect became more apparent as the task progressed, presumably as there were more “familiar” letters that had been and gone.

So, the headline message was that self-reported multitaskers are less adept at multitasking than those who shun multiple media. As someone who will admit to being an HMM, this is a disappointment. We could argue that the tests used in the study were surrogates – the real worldquestion would be “can you get work done appropriately whilst Twitter and E-mail are open on your dashboard and you are listening to your iPod?” not “can you remember if the red rectangles are in the same orientation if there are lots of blue ones there too?” I would also defend my position by acknowledging that my Twitter network is now a major source of information with “bang on the money” relevance for my work. Nevertheless I do know for myself that when I’ve really got to get something written I hide myself away with minimum distractions, the only added media will be background music to block out other noise, and this must be lyric-free to be fit for purpose! So, I will reflect on my work practice and perhaps make accessing of e-mail and Twitter more punctuated and less continuous, but I don’t feel that cutting off these channels entirely would – on balance – be a benefit. As the authors themselves point out, it may be that HMMs are demonstrating “a bias towards exploratory, rather than exploitative, information processing”.

Psychology and cognitive science are not my normal field of study and I therefore hope that I haven’t misrepresented any of the methods or findings of the PNAS paper in the proceeding discussion. I thought this was a truly interesting investigation, and highly topical – it is no longer just adolescents that are habitual multitaskers. Finally, from an educational research point of view, it was curious to note that participants in this research received course credits for their involvement in the study, both for taking the questionnaire in the first place and then for their role in the tasks themselves. I’m not sure we’d get away with that in a UK context.


1 Comment

  1. […] Doing several things at the same time like this is called task-switching.  You aren’t actually doing several things at once, but you have chosen to dilute your focus and switch between several tasks. […]

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