Canli et al. (2000)

Aim

• To find whether emotive images will be better remembered than pictures with little emotion.
• To find whether the amygdala is sensitive to different levels of emotional intensity to external stimuli, and whether the level of emotional intensity enhances the memory of that stimuli.

Background
There are 2 types of medical scans:

1. Functional scans show activity levels in different areas of the brain.
2. Structural scans take detailed pictures of the brain structure.

The study used an fMRI (functional Magnetic Resonance Imaging) which detects blood flow in the brain to show how the brain works during different tasks.
The amygdala is located in the brain's temporal lobe. It is responsible for the processing of emotion and storing of memory.

• Le Bar and Phelps (1998) suggested that emotional arousal aids the process of memory consolidation.
• Canli et al. (1999) found that strong amygdala activation resulted in improved memorisation of the causing stimuli. He wanted to replicate the study with repeated measures design rather than independent to make sure that the initial results were not due to chance.

Research Method, Design and Variables
A laboratory experiment was conducted.
The repeated measures design was implemented as participants were unexpectedly asked to repeat the procedure after 3 weeks.

Independent variable: level of arousal of each picture shown.
i) Not emotionally intense at all: Levels 1 & 2
ii) Extremely emotionally intense: Levels 3 & 4.

Dependent variable:

• The fMRI measure of amygdala activation. For each of the 96 scenes, 11 frames were captured.
• The memory of the scene after 3 weeks.

Sample
10 right-handed healthy female volunteers. Females were chosen as they would be more likely to report emotional experiences and show physiological reactions to the stimuli. The self-selecting sampling technique was used.

Procedure
Participants gave informed consent and were aware of the nature of the study. Individuals operating the fMRI scanner were trained and competent in the safety arrangements of the medical scan.

Participants viewed 96 scenes presented to them while in the fMRI scanner. All 96 scenes were from the 'International Affective Picture System' stimuli set. For the scenes used the valence ratings ranged from 1.17 (highly negative) to 5.44 (neutral). The order of scenes was randomised (to help overcome order effects). Each picture was presented for 2.88 seconds and there was an interval of 12.96 seconds where they viewed a fixation cross. During this, participants had to indicate their emotional arousal by pressing a button with their right hand. They had to choose from 4 buttons on a scale of 0 (not emotionally intense at all) - 3 (extremely emotionally intense).

To measure activity in the brain, fMRI data were collected by a 1.5 Tesla fMRI scanner, which is used to measure blood-oxygen-level-dependent contrast. Contrast imaging observes the different areas of the brain which are found active at any given time.

3 weeks after, participants were tested in an unexpected recognition test. They viewed the 96 scenes and 48 foils (newly added). Foils were selected to match previous scenes' valence ratings. Participants were asked to judge whether they had remembered it, felt it was familiar, or forgotten it.

Results

• The correlation between participants' intensity rating and valence was -0.66.
  The correlation between participants' intensity rating and arousal was 0.68.
  Therefore, participants' ratings of emotional intensity reflected well the valence and arousal characteristics of the stimuli.
• Amygdala activation was significantly correlated with higher ratings of individually experienced emotional intensity.
• The follow-up memory task indicated that memory performance was better for scenes rated as highly emotionally intense than for scenes rated as less emotionally intense.
• The degree of left amygdala activation predicted whether the stimuli would be forgotten, appear familiar, or would be remembered.

Conclusion

1. Canli found an association between individual experiences of emotional intensity for stimuli with amygdala activation and memory. The more emotionally intense an image is, the more likely it will be remembered.
   This provides evidence to explain why people remember emotionally intense experiences well.
2. The amygdala is sensitive to individuals' experienced emotional intensity of visual stimuli. The activity in the left amygdala during encoding is predictive of subsequent memory.

Strengths and Weaknesses

• As it was a lab experiment, there were standardised procedures: participants rated the same scenes; the time each scene and interval was presented was the same. Hence, there is internal validity, and there are fewer chances of confounding variables affecting the study.
• Quantitative data relating to amygdala activation and statistical analyses such as correlational analysis were collected. Therefore, the data is reliable (objective analysis) and easy to compare.
• The task isn't ecologically valid however, participants did not respond to demand characteristics, which increases validity.
• fMRI measures biological responses which is an objective finding as the researcher does not have to interpret any results. However, we do not know much about the locations of specific behaviours in the brain.
• The sample only consisted of right-handed females therefore, this introduces participant variables that could distort results and reduce validity. Thus, we can not really generalise results to males and left-handed individuals as they may respond differently.

Nature vs. Nurture
Machines such as fMRI have been used to measure biological responses. The biological processes underlying emotions are a product of the brain and hormones. OR (in other words) The biological processes causing emotions are a product of the brain and hormones. However, there are differences between individuals' emotional responses. Differences can be due to hormone levels or experiences.

Individual and Situational Explanations
Our tendency to cry at sad films indicates that situational factors matter in our expression of emotions. Although individual factors are present here too - not everyone cries at the same film.