Quirks and Quarks

Caffeine fail: New study shows it can keep you awake, but can't keep you functional

This study of 276 participants is the first to investigate the effect of caffeine on the ability to follow complex procedures after being deprived of sleep

Scientists found caffeine helped sleep-deprived participants in an attention task, but not in a procedural one

The findings of a new study suggests caffeine can help someone who's sleep-deprived remain alert, but not functional in complex procedural tasks. (John Gress JF / CN / REUTERS)

New research suggests a cup of coffee might help you feel more focused, but if you haven't been getting enough sleep, it won't help you with any kind of procedural task.

In a study published in the Journal of Experimental Psychology: Learning, Memory, & Cognition, scientists found caffeinated sleep-deprived individuals make as many mistakes performing a particular kind of complex task as people who are also sleep deprived but non-caffeinated.

Kimberly Fenn, an associate professor of psychology at Michigan State University, said they had people come into their lab in the evenings to complete two tasks. Half of them went home to sleep, to return in the morning. The other half were kept awake in the lab overnight. 

In the morning, half the test subjects got caffeine and the other half did not. After waiting for the caffeine to absorb, both groups performed both tasks again.

One task was to test for attention, the other to test for their ability to follow detailed instructions to accomplish a complex task — both while being interrupted.

The complex task was meant to simulate real world scenarios where people need to make many decisions in a certain order, like performing surgery, flying an airplane or operating heavy machinery.

Fenn says just because coffee helps you feel more awake, it doesn't mean you're capable of carrying out multistep tasks. (Carlo Allegri / REUTERS)

Fenn told Quirks & Quarks host Bob McDonald that while caffeine helped with the attention task, it did nothing to help those who were sleep-deprived in the more complex procedural task. 

She said it's important people remember caffeine isn't a replacement for a good night's sleep.

You can hear an interview with Kimberly Fenn by clicking the link above.

Produced by Sonya Buyting and Jim Lebans. Written by Sonya Buyting.