Not all time is created equal

Using your most productive time for the most important tasks

3-minute read

Welcome to another edition of Study of The Month: a monthly blog dedicated to thought-provoking research.   

One of the most powerful insights from our Productivity workshop at LifeLabs Learning is that not all time is created equal. Since our attention and energy levels are variable, we should use our most productive time for our most important tasks. But how do we know when we’re most productive -- especially when it comes to our cognition? 

This is a question that social psychologist Galen V. Bodenhausen posed in his 1990 study, “Stereotypes as Judgmental Heuristics: Evidence of Circadian Variations in Discrimination.” Specifically, Bodenhausen wanted to know if time of day impacted our ability to reason.  

To test this out, Bodenhausen had participants--who self-identified as either a “morning” or “evening person”--answer a tricky question at either 9AM or 8PM. The hypothesis was that a morning person will be less prone to judgmental error in the morning rather than evening, while an evening person would be the reverse.  


Do you think time of day mattered?

Animated GIF


Before unveiling the results, let’s look at the task participants were asked to solve. 

The Linda Problem

Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in anti-war demonstrations.

Which is more probable?

  • Linda is a bank teller.
  • Linda is a bank teller and is active in the feminist movement.

Intuition leads most people to select option 2.  But they are wrong (Tversky & Kahneman, 1981).  

Bank tellers who are also active in the feminist movement are a subcategory of bank tellers, and subcategories by definition are smaller than the whole they are a part of. Therefore, the probability that Linda is a bank teller is greater than the probability she is a bank teller and a feminist.  


In the Bodenhausen study, the vast majority of participants got the probability problem wrong, but it turned out that time of day mattered.  

  • 94% of participants with "morning personalities" committed the error during an evening experimental session, while only 71% did so in the morning. 
  • Conversely, participants with "evening personalities" were more likely to commit this fallacy during a morning experimental session (92%) than during the evening (70%).

table of morning and evening session study answers


Since not all time is created equal, we benefit from:     

  • Identifying when our cognitive resources are at their peak.  
  • Protecting that time (e.g., reducing interruptions). 
  • Using our prime time for our most important tasks.   

As always, we want to hear from you.  

What’s one way you have applied these insights or can apply them in the future?