One of the most common frameworks in the emotions field proposes that
affective experiences are best characterized by two main dimensions:
arousal and
valence. The dimension of valence ranges from highly positive to highly negative, whereas the dimension of arousal ranges from calming or soothing to
exciting or agitating. The majority of studies to date have focused on the arousal dimension of emotion as the critical factor contributing to the emotional enhancement effect on memory. Different explanations have been offered for this effect, according to the different stages of memory formation and reconstruction. Memory has been shown to be better with arousal linked with emotion than without emotion. The use of a
PET scan has allowed scientists to see that pictures with an "emotional-stimulus" have significantly larger amount of activity in the amygdala. However, a growing body of research is dedicated to the emotional valence dimension and its effects on memory. It has been claimed that this is an essential step towards a more complete understanding of emotion effects on memory.
Emotion and encoding From an
information processing perspective,
encoding refers to the process of interpreting incoming stimuli and combining the processed information. At the encoding level the following mechanisms have been suggested as
mediators of emotion effects on memory:
Selectivity of attention Easterbrook's (1959) cue utilization theory predicted that high levels of arousal will lead to
attention narrowing, defined as a decrease in the range of
cues from the stimulus and its environment to which the organism is sensitive. According to this hypothesis, attention will be focused primarily on the arousing details (cues) of the stimulus, so that information central to the source of the emotional arousal will be encoded while peripheral details will not. Accordingly, several studies have demonstrated that the presentation of emotionally-arousing stimuli (compared to neutral stimuli) results in enhanced memory for central details (details central to the appearance or meaning of the emotional stimuli) and impaired memory for peripheral details. Also consistent with this hypothesis are findings of
weapon focus effect, in which witnesses to a crime remember the gun or knife in great detail but not other details such as the perpetrator's clothing or vehicle. In
laboratory replications it was found that participants spend a disproportionate amount of time looking at a weapon in a scene, and this looking time is inversely related to the likelihood that individuals will subsequently identify the perpetrator of the crime. Other researchers have suggested arousal may also increase the duration of attentional focusing on the arousing stimuli, thus delaying the disengagement of attention from it. Ochsner (2000) summarized the different findings and suggested that by influencing attention selectivity and dwell time, arousing stimuli are more distinctively encoded, resulting in more accurate memory of those stimuli. While these previous studies focused on how emotion affects memory for emotionally arousing stimuli, in their arousal-biased competition theory, Mather and Sutherland (2011) argue that how arousal influences memory for non-emotional stimuli depends on the priority of those stimuli at the time of the arousal. Arousal enhances perception and memory of high priority stimuli but impairs perception and memory of low priority stimuli. Priority can be determined by bottom-up salience or by top-down goals.
Prioritized processing Emotional items also appear more likely to be processed when attention is limited, suggesting a facilitated or prioritized processing of emotional information. This effect was demonstrated using the
attentional blink paradigm in which 2 target items are presented in close temporal proximity within a stream of rapidly presented stimuli. The typical finding is that participants often miss the second target item, as if there were a "blink" of attention following the first target's presentation, reducing the likelihood that the second target stimulus is attended. However, when the second target stimulus elicits emotional arousal (a
"taboo" word), participants are less likely to miss the target's presentation, which suggests that under conditions of limited attention, arousing items are more likely to be processed than neutral items. Additional support for the prioritized processing hypothesis was provided by studies investigating the
visual extinction deficit. People suffering from this deficit can perceive a single stimulus in either side visual field if it is presented alone but are unaware of the same stimulus in the visual field opposed to the lesional side, if another stimulus is presented simultaneously on the lesional side. Emotion has been found to modulate the magnitude of the visual extinction deficit, so that items that signal emotional relevance (e.g., spiders) are more likely to be processed in the presence of competing distractors than nonemotional items (e.g., flowers).
Emotion and storage In addition to its effects during the encoding phase, emotional arousal appears to increase the likelihood of
memory consolidation during the retention (
storage) stage of memory (the process of creating a permanent record of the encoded information). A number of studies show that over time, memories for neutral stimuli decrease but memories for arousing stimuli remain the same or improve. Others have discovered that memory enhancements for emotional information tend to be greater after longer delays than after relatively short ones. This delayed effect is consistent with the proposal that emotionally-arousing memories are more likely to be converted into a relatively permanent trace, whereas memories for nonarousing events are more vulnerable to disruption. A few studies have even found that emotionally arousing stimuli enhance memory
only after a delay. The most famous of these was a study by Kleinsmith and Kaplan (1963) the Kleinsmith and Kaplan effects were most likely due to a methodological confound. However, Sharot and Phelps (2004) According to these theories, different
physiological systems, including those involved in the discharge of
hormones believed to affect memory consolidation, become active during, and closely following, the occurrence of arousing events. Another possible explanation for the findings of the emotional arousal delayed effect is post-event processing regarding the cause of the arousal. According to the post stimulus elaboration (PSE) hypothesis, Thus, if a person gives more thought to central details in an arousing event, memory for such information is likely to be enhanced. However, these processes could also disrupt consolidation of memories for peripheral details. Christianson (1992) suggested that the combined action of perceptual, attentional, and elaborative processing, triggered by an emotionally arousing experience, produces memory enhancements of details related to the emotion laden stimulus, at the cost of less elaboration and consolidation of memory for the peripheral details.
Emotion and elaboration The processes involved in this enhancement may be distinct from those mediating the enhanced memory for arousing items. It has been suggested that in contrast to the relatively automatic attentional modulation of memory for arousing information, memory for non-arousing positive or negative stimuli may benefit instead from
conscious encoding strategies, such as elaboration. Since words such as "
sorrow" or "
comfort" may be more likely to be associated with autobiographical experiences or self-
introspection than neutral words such as "shadow", autobiographical elaboration may explain the memory enhancement of non-arousing positive or negative items. Studies have shown that dividing attention at encoding decreases an individual's ability to utilize controlled encoding processes, such as autobiographical or semantic elaboration. Thus, findings that participants' memory for negative non-arousing words suffers with divided attention, and that the memory advantage for negative, non-arousing words can be eliminated when participants encode items while simultaneously performing a secondary task, has supported the elaborative processing hypothesis as the mechanism responsible for memory enhancement for negative non-arousing words.
Emotion and retrieval Retrieval is a process of reconstructing past experiences; this phenomenon of reconstruction is influenced by a number of different variables described below.
Trade-off between details Kensinger argues there are two trade-offs: central/peripheral trade-off of details and a specific/general trade-off. Emotional memories may include increased emotional details often with the trade-off of excluding background information. Research has shown that this trade-off effect cannot be explained exclusively by overt attention (measured by eye-tracking directed to emotional items during encoding) (Steinmetz & Kensinger, 2013).
Contextual effects of emotion on memory Contextual effects occur as a result of the degree of similarity between the encoding context and the retrieval context of an emotional dimension. The main findings are that the current
mood we are in affects what is attended, encoded and ultimately retrieved, as reflected in two similar but subtly different effects: the mood congruence effect and mood-state dependent retrieval. Positive encoding contexts have been connected to activity in the right fusiform gyrus. Negative encoding contexts have been correlated to activity in the right amygdala (Lewis & Critchley, 2003). However, Lewis and Critchley (2003) claim that it is not clear whether involvement of the emotional system in encoding memory differs for positive or negative emotions, or whether moods at recall lead to activity in the corresponding positive or negative neural networks.
Mood congruence effect The
mood congruence effect refers to the tendency of individuals to retrieve information more easily when it has the same emotional content as their current emotional state. For instance, being in a
depressed mood increases the tendency to remember negative events (Drace, 2013). This effect has been demonstrated for
explicit retrieval as well as
implicit retrieval.
Mood-state dependent retrieval Another documented phenomenon is the
mood-state dependent retrieval, a type of
context-dependent memory. The retrieval of information is more effective when the emotional state at the time of retrieval is similar to the emotional state at the time of encoding. Thus, the probability of remembering an event can be enhanced by evoking the emotional state experienced during its initial processing. These two phenomena, the
mood congruity effect, and mood-state dependent retrieval, are similar to the context effects which have been traditionally observed in memory research. It may also relate to the phenomena of
state-dependent memory in
neuropsychopharmacology. When recalling a memory, if someone is recalling an event by themselves or within a group of people, the emotions that they remember may change as well recall of specific details. Individuals recall events with stronger negative emotions than when a group is recalling the same event. Collaborative recall, as it can be referred to, causes strong emotions to fade. Emotional tone changes as well, with a difference of individual or collaborative recall so much that an individual will keep the tone of what was previously felt, but the group will have a more neutral tone. For example, if someone is recalling the negative experience of taking a difficult exam, then they will talk in a negative tone. However, when the group is recalling taking the exam, they will most likely recount it in a positive tone as the negative emotions and tones fade. Detail recount is also something that changed based on the emotion state a person is in when they are remembering an event. If an event is being collaboratively recalled the specific detail count is higher than if an individual is doing it. conducted a study in which participants saw a screen with five colors on it and when presented with the next screen were asked which color was missing. Those who were experiencing negative emotions were more precise than those in the positive and neutral conditions. Aside from emotional state, mental illness like depression relates to people's ability to recall specific details. Those who are depressed tend to overgeneralize their memories and are not able to remember as many specific details of any events as compared to those without depression.
Thematic vs. sudden appearance of emotional stimuli A somewhat different contextual effect stemmed from the recently made distinction between thematical and sudden appearance of an emotionally arousing event, suggesting that the occurrence of memory impairments depends on the way the emotional stimuli are induced. Laney et al. (2003) argued that when arousal is induced thematically (i.e., not through the sudden appearance of a discrete shocking stimulus such as a weapon but rather through involvement in an unfolding event plot and empathy with the victim as his or her plight becomes increasingly apparent), memory enhancements of details central to the emotional stimulus need not come at the expense of memory impairment of peripheral details. Laney et al. (2004) demonstrated this by using an audio narrative to give the presented slides either neutral or emotional meaning, instead of presenting shockingly salient visual stimuli. In one of the experiments, participants in both the neutral and emotional conditions viewed slides of a date scenario of a woman and man at a dinner date. The couple engaged in conversation, then, at the end of the evening, embraced. The event concluded with the man leaving and the woman phoning a friend. The accompanying audio recording informed participants in the neutral condition that the date went reasonably well, while participants in the emotional condition heard that, as the evening wore on, the man displayed some increasingly unpleasant traits of a type that was derogatory to women, and the embrace at the end of the evening was described as an attempt to sexually assault the woman. As expected, the results revealed that details central to the event were remembered more accurately when that event was emotional than when neutral, However, this was not at the expense of memory for peripheral (in this case, spatially peripheral or plot-irrelevant) details, which were also remembered more accurately when the event was emotional. Based on these findings it has been suggested that the dual enhancing and impairing effects on memory are not an inevitable consequence of emotional arousal. == Neurobiological mechanisms of emotional memory enhancement ==