Instructions on what is good to memorize and what is not help fix memories better than emotions: a study clarifies what consolidates memory.
“The following words are important, you must remember them“: Indications like this are very effective at fixing memories – they do it even better than negative emotions or a good night’s sleep. A study published in Frontiers in Behavioral Neuroscience suggests that we have more control over our memories than we thought. And that clear instructions on what is best to remember consolidate memory more than any other element considered so far.
Better than stress and sleep?
It has long been known that memories associated with mildly negative emotions, such as mild stress or contained fear, can become more indelible in the memory, even if prolonged exposure to intense negative emotions has the opposite effect (mental fog, learning difficulties and distortion of memories).
Another factor that positively affects memory is a good night’s sleep. But also try to remember something deliberately can have a favorable effect in consolidating memories. Which of these strategies, voluntary or otherwise, helps the most?
To remember, to forget
A group of scientists from Merrimack College, in Massachusetts, subjected two groups of participants to memorization tasks, 45 interviewed online and 53 met in the laboratory. Half of each group was given a hundred words to remember in the morning and had to remember them in the evening; the other half received the list in the evening and slept on it, taking the recall tests the following morning. The participants’ brain activity during sleep was measured with electroencephalography (EEG).
Half of the words on the list had negative emotional connotations, the other half, neutral. Furthermore, each word had a corresponding note with instructions indicating whether the term was to be remembered or forgotten.
Instructions vs emotions
Participants generally remembered better the words they had been explicitly asked to memorize: the instructions favored the consolidation of memories better than emotions. However, emotions also played a, let’s say, “enhancing” role: words that were accompanied by the label “to remember” and had negative connotations were more likely to be remembered.
As suggested by previous studies, however, words with emotional connotations were also more likely to generate false memories: they were more likely to be mistakenly placed in the group of those that absolutely must be memorized.
According to scientists, when we label something as worth remembering, the hippocampus (a brain structure crucial for memory) gives it priority, suppressing other irrelevant information.
Reducing interference improves recall during recall.
And sleep?
Against all expectations, whether or not the participants had slept had no effect on their ability to memorize the words. Or rather, it was not generally the sleep itself, but rather the brain activity that occurred during sleep, that influenced the ability to remember.
For example, higher levels of sleep spindles (a type of brain wave that resembles a series of spikes in the encephalogram) during REM sleep have been associated with better recall of negatively connoted words. Moreover, “sleep spindles are widely implicated in the transfer of information from the temporary memory of the hippocampus to more stable representations in the neocortex”, explains Laura Kurdziel, lead author of the study.
On the contrary, another type of sleep, slow wave sleep, was negatively correlated with the ability to remember. It may be – but it will need to be verified in new studies – that sleep selectively consolidates some types of memories and not all, for example those that are accompanied by emotional experiences.
