A very simple approach is if you have a team of subject matter experts and you want to get an unbiased estimate from them, instead of asking them for the estimate vocally during a meeting, ask them to write it on a piece of paper and give it to you.
Once you receive all the estimates you can share the results with the team but DON'T let them know who provided what estimate.
You could then either start a fresh round of estimation now that team members are aware of alternate options OR have an open discussion on the low and high estimates and then give the team a chance to re-estimate.
"Imagine if every Thursday your shoes exploded if you tied them the usual way. This happens to us all the time with computers, and nobody thinks of complaining."