The question of how our how our brains memorize daily experiences has intrigued cognitive psychologists and neuroscientists for decades. Amongst a range of theories attempting to explain how we encode and later recall information, a curious influence over memory encoding has been observed: our emotional state at the time of an event occurring can affect our ability to memorize details of it.
Moreover, emotions are believed to play a role in determining whether we can recall a stored memory at the time we try to revisit it. Coaxing ourselves into the same mood we were experiencing when we witnessed an event, for instance, has been found to often have a positive effect on our chances of recalling specific details relating to it.
It appears that emotionally charged situations can lead us to create longer lasting memories of the event. When we are led to experience feelings of delight, anger or other states of mind, vivid recollections are often more possible than during everyday situations in which we feel little or no emotional attachment to an event.
The findings of a series of studies have implied that emotion plays a role at various specific stages of remembering (encoding) information, consolidating memories and during the recall of experiences at a later date. For instance, cognitive psychologist Donald MacKay and a team of researchers asked participants to take part in an emotional Stroop test, in which they were presented with different words in quick succession. Each word was printed in a different color, and subjects were asked to name the color. They were also later asked to recall the words after the initial test. MacKay found that taboo words, which were intended to elicit an emotional response, were recalled more frequently than words which carried less emotional connotations (MacKay et al, 2004).1
The results of MacKay’s experiment, and others with similar outcomes, suggest that an emotive state at the time we perceive and process an observation can positively affect the encoding of information into the short or even long-term memory.
Although the emotional Stroop test demonstrates this link between emotion and memory, the role of emotion has been long suspected.
In 1977, researchers at Harvard published a paper entitled Flashbulb Memories, in which they noted that people are often able to vividly recollect where they were when an event occurred that was significant to them. They used the example of the assassination of U.S. president John F. Kennedy, but many people will hold similarly detailed memories of what they were doing when they learned of the terrorist attacks of September 11th, 2001 or the death of a famous person such as Elvis Presley or Michael Jackson. Unlike a photographic memory, these “flashbulb memories” tend only to occur only when the event is felt to be of particular significance to a person or when it causes a state of surprise, supporting the idea that a person’s emotional state at the time of an event can influence whether or not it is encoded as a memory (Brown and Kulik, 1977).2
Now, the idea that we would be more likely to remember an event of historical significance than a mundane observation during a commute to work may seem obvious. The assassination of JFK is often considered to have been one of the most significant events in U.S. 20th Century history, even by those who were born after the event and only learnt of it in history classes. However, another study in which participants were asked to complete questionnaires to gauge their recollection of the attempted assassination of Ronald Reagan suggested that the significance of an event tends to be less influential than the emotions experienced at the time of encoding. Pillemer (1984) found that people’s reported emotional state at the time of the assassination attempt helped to influence whether memories would be stored more than whether or not they merely rehearsed - considered or discussed - the memory afterwards.3
Why Would Emotions Influence Memory?
Whilst there appears to be mounting evidence in support of emotions’ role in memory, the question remains of why emotions, over judgements we exercise more control over, affect our encoding of events in this way. What purpose is served by being able to recall a distressing occasion that we would rather forget, better than the facts that we need to learn for an exam?
First, let us remember the evolutionary purpose served by emotional experiences. One theory suggests that our ability to experience distressing emotions, fear and anxiety is an inherited trait which has historically given our ancestors a survival advantage. Öhman and Mineka (2001) claimed that, as emotions tend to operate beyond our conscious control, their intuitive nature gives us an early warning of impending threats or dangers in our external environment (Öhman and Mineka, 2001).4 For example, whilst crossing through the powerful currents of a river, the feeling of fear alerts us to the danger to our lives and helps to ensure that we pay attention to hazards. Negative emotions may also deter us from engaging in such activities in the first place! Similarly, feelings of happiness created by a secure environment, such as a home, warm and free from threats, may encourage us to continue risk-averse, adaptive behavior.
Attention, Emotion and Memory
Whilst the emotional distortion of memory encoding and recall seems to be counter-productive to the maintenance of an accurate view of the outside world, their influence may be better understood in terms of how it affects our attention, and how subject of our focus in turn affects what our memories encode.
Research suggests that our brains are more likely to focus on stimuli of emotional significance. This was demonstrated in a study in which participants were shown a control set of emotionally neutral images with pictures such as those depicting various injuries, eliciting an emotional response. Schupp et al (2007) found that subjects’ attention increased when emotional images were displayed to them, suggesting that our attention is instinctively drawn to emotive subjects.5
As we tend to remember by focussing and elaborating on an observation, this may go some way to helping us to understand why emotions influence memories.
Although emotions can draw our attention to subjects, their influence on our conscious experience of the world does not end here. After switching our attention from one subject to another, a brief phenomenon may occur, known as an attentional blink, during which we are unable to fully focus on the second stimuli.
As a result, we may remember something less well if we have been focussing on something else immediately beforehand. Studies have suggested that there is an emotional component to this attentional blink.
In one experiment, researchers were able to limit participants’ ability to remember neutral information by presenting them with an emotive stimuli very shortly beforehand (Smith et al, 2006).6
Mood Congruence Effect
A person’s focus of attention will inevitably affect what they remember during an experience, but emotions appear to affect memory encoding more profoundly than simply drawing attention to a particular emotive subject over a neutral one.
Your emotional state at the time of an event can help to determine whether or not your observations during it will be stored ready for recall later on.
One study found that the subjects of an experiment were more able to associate with stories whose content matched their moods at the time of them being recounted to them. A happy person, for example, may associate more with characters who are positive and enthusiastic, whilst a sad person may identify with a character who is the subject of persecution. Gordon Bower, who conducted the study, found that this mood congruence effect - an association with stimuli which reflect our current mood - influenced people’s ability to remember information (Bower, 1981).7 The result of this effect is that you may be more able to recall having read a negative report in a newspaper if you were in a low mood, rather than happy, at the time of reading it.
Role of the Amygdalae
The means by which emotions are able help determine which memories are processed is also the subject of ongoing studies.
Whilst the process is still not fully understood, it is believed that the hippocampus and two amygdalae regions in the brain play key roles in processing both memories and emotions, and that interactions between the two may reinforce the link between memory and emotions.
One study which used tomography to monitor the amygdala found increased activity when remembering emotive stimuli, whether they were of a positive or negative nature.
Hamann et al (1999) also proposed that one role of the amygdala is to “modulate” activity in the hippocampus, which is believed to play a role in the formation of new memories (Hamann et al, 1999).8
Rehearsal and Retrieval
Whilst emotions are believed to affect the transformation of events into memories at the point of encoding, our mood whilst trying to recall events at a later date can affect our ability to access those memories.
In a joyous mood, we may be able to better remember past events that brought joy to us. For example, whilst on a beach, you may be able to recall happy memories of a memorable family gathering over a negative event. In contrast but following the same principle, whilst in a low mood, you may recall sad memories more easily. This correlation between our mood at the point of recall and the type of memories we able to recall is known as the mood-state dependent memory.
James Laird of Clark University demonstrated this effect in a series of experiments, in which they were able to artificially induce moods by varying participants’ facial expressions accordingly.
When subjects were asked to perform expressions which would create a fearful expression, for instance, they reported increased feelings of fear. Laird and his fellow researchers found that the induced mood then affected the memories that a participant was able to access - someone experiencing some emotions, such as fear, may be better able to remember other memories of similarly fearful events than when they are in a more emotional neutral state (Laird et al, 1989).9 This research appears to support the idea that memory recall is often mood-state dependent.
Emotions and Forgetting
If emotions help to determine whether or not a memory is consolidated into the long-term memory, it seems equally plausible that the emotions associated with a memory may influence a person’s ability to access it.
Psychoanalyst Sigmund Freud was one of the first people in the field of psychology to investigate the emotional associations linked to memories. Freud felt that memories of particularly traumatic events, or those which would cause distress to a person if dwelled upon them, may be repressed.
Such memories are not entirely forgotten, but the conscious mind is prevented from recalling them in case, according to Freud, they created feelings of guilt or shame. Instead, they remain in the unconscious mind and affect us in ways that we do not realise. In a series of studies, Freud identified repressed feelings and memories as being the source of various phobias, for instance.
Using regression in a state of hypnosis, along with techniques such as free association, Freud believed that these memories could be brought back into the conscious mind so that a person may accept them and resolve issues associated with such repressed memories.
Rose-Tinted Glasses? The Fading Affect Bias
More recently, the effect of emotions on the memories that we forget has been identified in the form of the fading affect bias. This bias leads us to tend to forget memories of negative emotional valence and focus on memories which affect us more positively. Idealised memories of childhood, for instance, may be due to our minds focussing on the positive, rather than negative, events that occurred whilst growing up.
This fading affect bias was demonstrated in a 2009 study which tested the memory recall of hundreds of participants, and found that memories of a positive valence, when recalled to others, are more likely to remain accessible than those of a negative valence (Walker et al, 2009).10
The findings of these experiments support the results of a separate study in which hundreds of nuns were questioned regarding prior life events. Researchers found that the older participants were, the more they tended to recall memories of a positive valence than negative events (Kennedy, Mather and Cartensen, 2004).11 The older we get, it appears, the more we may view the past through ‘rose-tinted glasses’.
Effect of Suppressing Emotions
Can our conscious efforts to change our emotions during an event alter the way in which they affect our memories’ encoding of the experience?
Researchers at Stanford university tested this idea with experiments in which participants were shown varying stimuli such as a video. During the experiments, some participants were asked to suppress their emotions and not allow them to show to others. Afterwards, their ability to recall the stimuli presented to them was measured. Interestingly, people who had attempted to suppress their emotions tended to demonstrate an impaired ability to recall their experience afterwards compared to those who allowed their emotional state to show (Richards and Gross, 2000).12 One explanation for the results of this study is that a conscious focus on, and self-awareness of, one’s emotional state may detract from a person’s observation of their environment, including external stimuli such as the video.
The way in which we allow signs of our emotions to show is not the only factor to affect the link between memory and emotional state. Gender differences, too, seem to influence memory, with males and females handling emotive memories differently.
fMRI scans conducted on people carrying our memory tasks whilst in a negative emotional state have revealed differences in how the brain processes information whilst a particular emotional state is being experienced. The scans revealed that activity may be focussed in the amygdala, as discussed earlier, in females compared to males (Koch et al, 2007).13
Further gender differences between the way memories are handled in males and females in an emotional state have also been found. Sabrina Kuhlmann and her colleagues carried out a study which tested the effect that cortisol, which is often released during stressful experiences, has memory recall. After inducing a state of stress and conducting a memory task, Kuhlmann found that the release of cortisol had a significant effect on male participants’ memories which did not occur to the same extent in females (Kuhlmann et al, 2001).14
The role that emotions play in our ability to encode and recall information may seem an inevitable, uncontrollable aspect of everyday life. However, the way in which emotions distort our perception and recollection of reality has implications beyond the study of psychology.
Take eyewitness testimonies in court cases, for example. Such valuable forms of evidence can play a key role in the legal process and in securing convictions. The reliability of eyewitness testimonies has become a subject of focus in recent years, with the influence of interrogation techniques and other factors being found to sometimes affect witnesses’ recall of events.