Mindfulness meditation is associated with various positive benefits, one of which is improved attention, but it might not be all good. A new study suggests that it may have negative cognitive consequences.
The study included three experiments, in the first two of which undergraduates carried out a 15-minute guided exercise: one group was instructed to focus attention on their breathing without judgment (mindfulness group); the other group was told to think about whatever came to mind (mind-wandering group; the control).
In the first experiment, 153 participants then studied a list of 15 words related to the concept of trash, but not including the word "trash". When then asked to recall as many of the words from the list as they could remember, 39% of the mindfulness group falsely recalled seeing the word "trash" on the list compared to only 20% of the mind-wandering group. There was no difference between the groups in the number of other words falsely recalled.
In the second experiment, 140 participants were compared to themselves, before and after the intervention. They all began by doing six of the same sort of word lists. They were then randomly assigned either the meditation exercise or the mind-wandering. This was then followed by a further six word lists.
Again, mindfulness participants were more likely to falsely recall the critical word than those who engaged in mind wandering. Those in the mind-wandering group showed no difference in performance on the word lists before and after, while those in the meditation group were significantly more likely to falsely remember the critical item. Again, there were no other differences in performance between the groups: they correctly recalled about the same number of words, and they falsely remembered about the same number of other words.
In the third experiment, 215 undergraduates had to determine whether a word had been presented earlier, where the words shown were all part of a strongly associated pair (e.g., foot-shoe). After seeing the 100 words (for 1.5 seconds each), they were then tested. Each word had an equal chance of being one of the words in the presented list, or its associated pair. All students were then given the 15-minute meditation exercise, before going through the process again.
Again, the rate of words correctly identified as seen before was about the same before and after the meditation exercise, but the rate of words falsely identified increased significantly after the exercise.
In all, then, it seems that mindfulness meditation increased participants' susceptibility to false memories, reducing their ability to differentiate items they actually encountered from items they only imagined (because of their strong association to the items encountered).
The researchers speculate that the mechanism that seems to underlie the benefits of mindfulness — judgment-free thoughts and feelings — might also affect people's ability to determine the origin of a given memory (source memory), because they have become less able to distinguish between externally occurring events and internally generated events.
Source memory is one of those memory domains that tend to be affected by aging. However, the benefits of meditation for improving attention — another area particularly affected by age — outweigh this downside. So I'm certainly not suggesting anyone should be put off by this finding!
An interesting question that remains to be answered is whether this negative effect on source memory is short-lived, or whether experienced meditators tend to have poorer source memory.
 . Increased False-Memory Susceptibility After Mindfulness Meditation. Psychological Science [Internet]. 2015 :0956797615593705. Available from: http://pss.sagepub.com/content/early/2015/09/03/0956797615593705