Title: Effects of Arousal level on Memory: A Review of Emotion and Memory Research
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Abstract
This paper examines the relationship between emotion and memory through a review of research literature. Emotions are known to influence memory in a variety of ways. Research suggests that high arousal emotional events are generally better remembered than low arousal or neutral events. The mechanisms behind this effect are complex. Memory is better for central details of high arousal events compared to peripheral details. Emotions also appear to affect memory through physiological arousal and hippocampal-amygdala interactions in the brain. This paper reviews several landmark studies that explored these complex relationships between emotion and memory. The studies demonstrate that while high arousal enhances memory for some details, it can also impair memory for other details due to narrowing of attention. Overall, research shows emotions powerfully modulate memory through both physiological arousal and cognitive pathways in the brain. A better understanding of emotion-memory relationships has implications for eyewitness testimony, trauma recovery, and education.
Keywords: emotion, memory, arousal, amygdala, hippocampus, eyewitness testimony, trauma
Effects of Arousal Level on Memory: A Review of Emotion and Memory Research
It is well established that emotions influence memory in complex ways. Landmark studies by Cahill and McGaugh (1996), Christianson (1992), and others have demonstrated that highly arousing emotional events tend to be better remembered than low arousal or neutral events. The effects of emotion on memory are complex, as emotions appear to both enhance memory for some details while impairing it for others. This paper will review classic and current research to better understand the relationships between emotion, arousal, cognition, and memory. An improved understanding of these relationships has important implications for areas like eyewitness testimony, trauma recovery, and education.
The Yerkes-Dodson law provides a basic theoretical framework for understanding how arousal levels impact performance and memory (Yerkes & Dodson, 1908). According to this law, low or high arousal is less optimal for tasks than moderate arousal. Relating this to memory, moderate emotional arousal is thought to optimize memory encoding because it energizes the brain without overloading it. At very high levels of arousal, the stress response may impair memory encoding. Research on discrete emotions also suggests there are differences in how specific emotions like sadness versus anger versus happiness may affect memory (Kensinger & Schacter, 2008; Shiota & Keltner, 2021).
Memory and Emotions in the Brain
At the neurobiological level, memories are made in the hippocampus and surrounding medial temporal lobe structures. Emotions also greatly impact memory processes. The amygdala plays a key role in processing emotionally arousing experiences (Phelps, 2004). When the amygdala detects an arousing stimuli, it initiates a cascade of physiological arousal responses like increased heart rate and cortisol release. Meanwhile, the amygdala interacts strongly with the hippocampus during memory encoding and consolidation (McGaugh, 2015). Laboratory studies of memory and emotion provide evidence that physiological arousal sparked by the amygdala during emotional experiences strengthens hippocampal memory traces (Cahill & McGaugh, 1996; Christianson & Mjorndal, 1985; Kensinger, 2009).
Central versus Peripheral Memory in Emotion
Research suggests emotional arousal enhances memory mainly for central details of emotional events versus peripheral details. Christianson (1992) had participants view a disturbing film of an actual violent crime and later tested their memory. Participants remembered central details like the victim’s expression, but had impaired memory for peripheral numerical details like times shown. In a real-world example, hospital patients had better memory for central versus peripheral details of their emergency treatment (Laney et al., 2004). Thus while emotions strengthen memory for what’s important, attentional narrowing under stress can impair memory for less important peripheral information (Reisberg & Heuer, 2004; Smeets et al., 2008).
Effects of Emotion on Long Term Memory
The effects of emotions on long-term memory have also been investigated. Studies using word lists have shown that emotionally arousing words are better remembered than neutral words over periods of weeks or more. For example, participants in one study were much better at identifying emotional words versus neutral words when tested a week later (Dolcos et al., 2005). Further work suggests emotional arousal intensifies and “tags” memories to receive preferential consolidation and storage in the brain. Emotionally arousing experiences continue to receive additional processing even after the initial memories have been consolidated, making them less prone to forgetting over time compared to neutral memories (McGaugh, 2015).
Emotions and Remembering Context
While emotions strengthen memory for event details, they can also impair memory for the specific context or source of the memory. For example, participants remember emotional pictures better than neutral ones, but are worse at correctly identifying which list the picture came from (Mather, 2007). Related work found people more confidently recalled emotional versus neutral words, but were less accurate about identifying physical font color details from the original encoding context (Sharot & Phelps, 2004). Thus emotion enhances memory for “what” happened but may impair memory for “when” or “where” it happened due to a narrowing of attention resources during encoding of emotional experiences.
Eyewitness Emotion and Memory Accuracy
Due to their relevance for criminal justice proceedings, studies have also examined how emotion affects eyewitness memory accuracy. In one meta-analysis, eyewitnesses showed better recall for emotional versus neutral details of a crime, however their recall of peripheral details was worse (Christianson, 1992). Critically, eyewitnesses also exhibited higher rates of false memories for misleading post-event information when recalling emotional crimes versus neutral details (Porter & Peace, 2007). In another study, angry eyewitnesses had lower identification accuracy than fearful or neutral eyewitnesses (Devenport et al., 2002). Thus while emotions intensify memory strength, they may also increase suggestibility and impair source monitoring abilities important for accurate eyewitness testimony. This research highlights the complex interactions between emotion, memory, and cognition.
Emotion and Traumatic Memory
Research also has implications for understanding trauma-related memory issues seen in conditions like post-traumatic stress disorder (PTSD). While emotional arousal tags traumatic memories to receive preferential consolidation in the brain, people with PTSD tend to have impaired context-dependent memory surrounding the trauma. As a result, trauma memories are disorganized and lack context, perpetuating unwanted reexperiencing and impaired social functioning (McNally et al., 2021). Overgeneral memory and impaired context-dependent memory seen in PTSD relates to similar impairment of memory for spatial and temporal source memory found in studies of emotional memory. Therapies thus aim to gradually add context to traumatic memories in a safe therapeutic setting to reduce impairment.
Education and Arousing Classroom Curricula
The effects of emotion on memory also hold practical implications for education. Studies find that including emotionally arousing material in curricula enhances long-term retention compared to dry presentations of fact alone. For example, students presented with stories about scientific concepts showed better memory weeks later than those who just read facts (Morris et al., 1977). Research also suggests simply attaching an emotional tag like excitement to learning material, through comedy or suspense for example, can facilitate later memory even if the tag is unrelated to content itself (Bui et al., 2013; Hunter, 2019). Carefully designing curricula to include emotionally engaging elements could optimize student achievement and memory of classroom material over the long term.
Conclusions
Research demonstrates emotions powerfully affect human memory through both physiological arousal and cognitive pathways in the brain. While emotional arousal enhances memory strength and persistence over time for central event details, it can also impair memory for peripheral contextual details and increase suggestibility, through attentional narrowing and interaction between the amygdala and hippocampus. Understanding these complex relationships between emotion and memory has implications for domains like trauma recovery, eyewitness testimony, education and more. Future research should continue exploring the effects of discrete emotions like happiness, sadness and disgust on cognitive processes from encoding to retrieval. Overall, emotions play a crucial role in shaping human memory in both adaptive and sometimes maladaptive ways.
Andrew Stroud