What do Will Smith and The Lion King Have in Common? 

The Effects of Emotion on Memory Recall in Males and Females

P.I.: Arsalaan Salehani (salehaniaa@email.wofford.edu)

Faculty Supervisor: David W. Pittman, Ph.D.

 

Introduction

            Although, the effects of emotion on memory have been studied in various studies, the conclusions have been varied.  Within the brain, the limbic system is responsible for emotions (see Image 1).  This system is composed of structures such as the hippocampus, the amygdala, and the hypothalamus.  Importantly, the hippocampus is also involved in learning (Purves, 2008).  This neuroanatomical organization implies a relationship between emotion and memory. Thus, studies have investigated the existence of this relationship and found that the amygdala may also play a role.  It has been suggested that emotion’s effects on memory consolidation are mediated by the amygdala, and lesion studies damaging a specific part of the amygdala have shown a subsequent lack of stimulation in a specific region of the hippocampus (Wang and Fu, 2011).  Therefore, if the amygdala and hippocampus are activated by emotionally charged stimuli, an individual may be able to remember pieces of information more efficiently.

            An extensive literature search did not yield many studies looking at the effects of emotion on memory across gender.  Stereotypically, women are expected to be more emotional, and so one may hypothesize a larger effect of emotion on memory in females rather than males.  An Australian study examined the frequency and intensity of certain emotions across gender.  In addition to other emotions, females more frequently self-reported joy and sadness as well as self-reporting sadness as one of the most intense emotions experienced.  Males more frequently and intensely self-reported pride (Brebner, 2003).  In terms of memory recall ability across gender, a 2010 study found females to outperform males in a recall task.  The investigators hypothesized that being a male was associated with fewer gains in acquiring information and greater losses in retaining information, with possible reasons including differences in brain structure and efficient use of white matter (Krueger and Salthouse, 2010).  Within this context, Sharot and Yonelinas suggest that emotion has a role in slowing the process of forgetting by enhancing memory consolidation.  Specifically, these investigators found that emotion slowed the effects of forgetting associated with studied events but not necessarily the context of those events (Sharot and Yonelinas, 2008).

            There is a widespread belief that emotional or traumatic events are remembered well due to their emotional aspects, sometimes called “flashbulb” memories.  However, the majority of scientific research points in the other direction, namely that emotional stress has adverse effects on memory for details, particularly when dealing with a negative emotional context.  In line with these studies, as described by Bornstein et al., Loftus and Burns conducted an experiment in 1987 to determine the impact of a disturbing film clip on recall and recognition.  Their results show that the emotionally arousing event itself is remembered well, however, memory for peripheral information and details does not benefit from emotion (Bornstein et al., 1998).  In contrast, Wang and Fu found that negative emotion enhanced the consolidation of item memory in females.  In males, this study found no significant effects of either negative or positive emotions on memory (Wang and Fu, 2010).

            As background information for some of the techniques in the current study, the nervous system is divided into two divisions, i.e. somatic and autonomic.  For our purposes, we will be focusing on the autonomic nervous system (ANS), which is further divided into the sympathetic and parasympathetic nervous systems (SNS and PNS, respectively).  The SNS controls the “fight or flight” response by becoming activated in times of stress, for example exposure to emotionally charged stimuli.  One of the effects of SNS activation is increased sweat production.  This, in turn, increases the conductance of the skin, which can be measured quantitatively as the galvanic skin response (GSR).

            In addition to GSR, the current study relies on electroencephalogram (EEG) measurements as indicators of brain activity, specifically through the measurement of the alpha and beta waves of the EEG.  According to an EEG Biopac Student Lab handout, alpha waves predominate in an awake yet relaxed position with the eyes closed.  In contrast, beta waves predominate in a state alert and attentive to external stimuli (Pflanzer et al., 2007).

            The purpose of this experiment was to determine any differences in memory abilities, GSR, and EEG measurements in emotionally charged sad and happy conditions across gender.  It was hypothesized that women would be affected more by the emotionally charged stimuli, as quantified by greater changes in the variability of GSR and EEG measurements as compared to males.  In addition, based upon the previous research in the field, it is expected that the sad emotional condition will yield a greater recall of information as compared to the happy condition, both in males and females. 

Methodology

Subjects: Subjects were 16 undergraduate students at Wofford College, ages ranged from 18-22.  However, due to difficulties with the equipment, final analyses were only conducted on data from 9 subjects, i.e. 6 males and 3 females.

Equipment: Equipment used in this experiment involved the following items:

·        The Biopac GSR System and equipment used to measure the galvanic skin response.

·        The Biopac EEG System and equipment used to measure brain activity (see Image 2).

·        An emotionally charged 2:30 “sad” video of scenes from the Will Smith movie Seven Pounds (see Image 3).

·        An emotionally charged 2:30 “happy” video of “I Just Can’t Wait to be King” from the movie The Lion King (see Image 4).

·        Two randomly generated 15-word lists.

·        An oral quiz on the details from each video clip.

Experimental Protocol:  Subjects were recruited via email and text message on a volunteer basis.  Subjects signed a consent form that addressed the possible hazards and regulations surrounding the experiment, in addition to entering them into a drawing for a $20 Pizza Hut gift card as incentive for participation.  There was a “happy” trial and a “sad” trial that each subject completed while GSR and EEG measurements were being recorded and word lists were being memorized.  EEG measurements were recorded from the prefrontal cortex due to its role in planning complex cognitive behaviors such as memory.  Eight of the subjects were randomly selected to do the “happy” trial first and the “sad” trial second in order to prevent the confounding variable of improved memory after the first trial.  The order of emotionally charged trials was reversed for the other eight subjects.  Baseline GSR and EEG readings were recorded while the subject relaxed for one minute, and the recordings were continued throughout the experimental protocol.  Thereafter, subjects were given one minute to memorize a list of 15 words, which was followed by their watching of either the “sad” or “happy” video clip for approximately 2 minutes and 30 seconds.  Following this interval, subjects were asked to write down as many of the words as they could remember in one minute.  Then, subjects were given one minute to orally answer 15 questions regarding the emotionally charged video.  This protocol, beginning from the baseline recordings, was then repeated for the other emotional condition.  The following data parameters were obtained:  mean average of GSR measurements in each section of the experiment, the standard deviation of the EEG recordings, and the number of words and video-related information successfully recalled.  These GSR measurements, EEG recordings, and recall test results were then analyzed for an interaction between emotion, gender, and memory.  Dependent variables included GSR measurements, EEG measurements, and the number of words and video information items correctly recalled.  The independent variables included the “happy” and “sad” emotional conditions.  A repeated measures analysis of variance (ANOVA) was performed using SPSS software to analyze the GSR, EEG, and recall task data.  P-values less than 0.05 were considered statistically significant, however, results with p-values close to 0.05 have also been included in the results.

Results

EEG

Figure 1: The effects of emotion and task on overall brain activity.

As demonstrated by figure 1, there was an interaction between emotion and task, 4.803(1,7), p=0.065, on overall brain activity.  In the sad condition, the word recall task led to slightly greater variability in overall brain activity, whereas the video information recall task led to less variability compared to baseline.  In comparison, in the happy condition, the word recall task led to less variability in overall brain activity, and the video information recall led to more variability compared to baseline.

Figure 2: The effects of emotion and gender on alpha and beta EEG waves.

As demonstrated by figure 2, there was an interaction between emotion, EEG wave, and sex, 4.008(1,7), p=0.085.  In males, both the sad and happy conditions led to greater variability in the alpha and beta waves of the EEG compared to baseline.  In comparison, females showed a decrease in variability in both the alpha and beta EEG waves for the sad condition compared to baseline.  However, in the happy condition, the alpha wave demonstrated slightly more variability, while the beta wave showed slightly less variability compared to baseline.

Figure 3: The effects of task on alpha and beta EEG waves in left vs. right brain hemispheres.

As demonstrated by figure 3, there was an interaction between task, hemisphere, and EEG wave, 3.685(1,7), p=0.096.  For the video information recall, both hemispheres of the brain demonstrated a greater variability in the alpha and beta EEG waves compared to baseline.  For the word recall task, the right hemisphere also showed this increase in variability of the alpha and beta waves compared to baseline, whereas the left hemisphere demonstrated decreased variability for both the alpha and beta EEG waves compared to baseline.

GSR

 

Figure 4: The effects of task on GSR.

As demonstrated by figure 4, there was a main effect of task, 13.152(1,12), p=0.003, on GSR recordings.  For both word recall and video information recall, GSR recordings demonstrated more variability compared to baseline.

 

Figure 5: The effects of task on GSR in males vs. females.

As demonstrated by figure 5, there was an interaction between sex and task, 3.606(1,12), p=0.082, on GSR recordings. For males, both the word recall task and video information recall task led to an increase in variability in GSR recordings compared to baseline.  For females, the word recall task also showed slightly increased variability in the GSR recordings, however, the video information recall task showed a slight decrease in variability of GSR recordings compared to baseline.

 

Figure 6: The effects of emotion and task on GSR in males vs. females.

As demonstrated by figure 6, there was an interaction between emotion, task, and sex, 3.459(1,12), p=0.088, on GSR recordings.  In males, the word recall and video information recall tasks both led to an increased variability in GSR recordings in both the sad and happy condition compared to baseline.  For females, the sad condition again led to an increase in variability in GSR recordings, however, in the happy condition, only the word recall led to increased variability compared to baseline.  In contrast, the video information recall task for females in the happy condition led to decreased variability of GSR recordings compared to baseline.

 Behavioral

Figure 7: Effects of task on recall.

As demonstrated by figure 7, there was a main effect of task, 26.222(1,14), p<0.001, on the number of items of information successfully recalled.  Subjects recalled more words than information about the video.

 

Figure 8: The effects of emotion and task on recall

As demonstrated by figure 8, there was an interaction between emotion and task, 8.387(1,14), p=0.012, on the number of items of information successfully recalled.  In both the happy and sad conditions, subjects recalled more words than information about the video.

Discussion

            Based on the work of previous studies, it is believed that emotionally charged stimuli improve memory function, and that this is effect is different across gender.  With these studies in mind, the current study was designed to investigate the interaction between gender, emotion, and memory.  It was hypothesized that women would be affected more by the emotionally charged stimuli, as quantified by greater changes in the variability of GSR and EEG measurements as compared to males.  In addition, based upon the previous research in the field, it is expected that the sad emotional condition will yield a greater recall of information as compared to the happy condition, both in males and females.  Based on the results of this study, the first hypothesis was not supported.  Keeping in mind that “1” on the y-axis represents no change from baseline, if we look at figures 2 and 6, we see that male EEG and GSR measurements showed a greater change than female measurements of EEG and GSR in response to the emotional condition.  Now moving our attention to figure 8, we see that the second hypothesis of this experiment was also not supported.  In contrast to several previous studies, the sad emotionally charged stimuli was not shown to definitively increase recall of information.  The number of words successfully recalled in the happy condition was greater than the number recalled in the sad condition.  However, the number of items recalled about the video is slightly higher for the sad condition as compared to the happy condition.  Perhaps this is a manifestation of the idea that the sad event itself is remembered better but not necessarily the details within it.  Other interesting findings include video recall in the happy condition causing the greatest change in overall brain activity (figure 1), the left brain being more activated by video recall than word recall (figure 3), word recall causing a greater activation of the SNS than video recall as quantified by GSR measurements (figure 4), and subjects being able to successfully recall more words than information about the videos (figure 7).  Only data analysis represented by figures 4, 7, and 8 demonstrated statistically significant differences amongst the conditions, however, data represented by the other figures was close to attaining statistical significance.  Future studies with a larger sample size and perhaps more powerful emotionally charged stimuli may lead to more significant results.  In addition, it is possible that the details in the sad versus happy videos were not of equal salience or interest to the subjects, or that subjects had a preference or greater familiarity with Seven Pounds or The Lion King prior to partaking in the experiment.  Thus, subjects could have come into the experiment knowing answers to the video information recall questions.  Continued research regarding the interaction of gender, emotion, and memory could give society vital information about disorders such as depression, and its different effects on males versus females.  In addition, these studies could be extended to the work or school environment to investigate the effects of emotions on performance and concentration in males versus females in emotional situations.

Images

Image 1: The Limbic System (http://www.cafleurebon.com/wp-content/uploads/2011/06/limbic.jpg)

Image 2: Biopac EEG System and equipment used to measure brain activity (http://www.pram.univ-montp1.fr/imagesmateriel/EEG.jpg)

Image 3: Will Smith in Seven Pounds (http://2.bp.blogspot.com/_vWsITEYdSEg/SZqGt3C-sXI/AAAAAAAAAqM/_doFyYT5HOI/s400/Seven+Pounds.jpg)              

Image 4: The Lion King (http://s-tlk.org/news/tlk-new-poster.jpg)

Image 5: Prefrontal cortex (http://www.humansoul.com/Prefrontal%20cortex.jpg)

Bibliography

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Pflanzer R, Uyehara J, McMullen W. 2007. Lesson 3: Electroencephalography I. Biopac Systems, Inc. Biopac Student Lab.

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