11.1 Can we reduce intrusions of traumatic memories?

One of the hallmarks of post-traumatic stress disorder is that memories of the traumatic event “intrude” on everyday life, popping up when they are not wanted. When you remember a previous event, the memory is said to be “active”. According to reconsolidation theory, active memories can also be changed. For example, when you tell a story from memory, telling the story might change your memory such that you would tell it differently next time. Reconsolidation theory suggests that one way to reduce intrusions of traumatic memories is to “activate” them and then change them so they are less likely to intrude on everyday life.

One way to modify intrusive memories was studied by James et al. (2015). They thought that playing a video game, namely Tetris, while a memory was active would help make that memory less traumatic. They had participants first view a traumatic film (including scenes of real car accidents). Over the next week, participants recorded how often a memory of the traumatic film intruded on their everyday life. During that week, participants came back into the lab and were randomly assigned to one of four treatment conditions:

• Reactivation-plus-Tetris: In this group, participants were shown still images from the traumatic film to “reactivate” memories for the film. They then played Tetris for 12 minutes.
• Reactivation only: In this group, participants were shown still images from the traumatic film to “reactivate” memories for the film, but then sat silently for 12 minutes and did not play Tetris.
• Tetris only: In this group, participants were not shown any images from the film but simply played Tetris for 12 minutes.
• No task (control): In this group, participants simply sat quietly for 12 minutes.

According to reconsolidation theory, people in the reactivation-plus-Tetris condition should experience fewer intrusive memories because playing Tetris should change those memories to be less disruptive. This is not predicted to happen in any other group. In the control and Tetris-only conditions, the original traumatic memories are not being reactivated, so they should not be affected. In the reactivation-only condition, although memories are being reactivated, they are not being altered. Of course, this is just what the theory says should happen. Let’s see what actually transpired.

tetris_data %>%
    mutate(effect = ___ - ___)

tetris_data %>%
    mutate(effect = ___ - ___) %>%
    ggplot(aes(x = ___, y = ___)) +
    geom_boxplot()

obs_f <- tetris_data %>%
    mutate(effect = ___ - ___) %>%
    specify(___ ~ ___) %>%
    calculate(stat = "F")

obs_f

null_dist <- tetris_data %>%
    mutate(effect = ___ - ___) %>%
    specify(___ ~ ___) %>%
    hypothesize(null = "___") %>%
    generate(reps = 1000, type = "___") %>%
    calculate(stat = "F")

null_dist %>%
    visualize() +
    shade_p_value(obs_stat = obs_f, direction = "greater")

null_dist %>%
    visualize(method = "both") +
    shade_p_value(obs_stat = obs_f, direction = "greater")

tetris_data_effect <- tetris_data %>%
    mutate(effect = ___ - ___)

lm(___ ~ ___, data = tetris_data_effect) %>%
    anova()

with(
    tetris_data %>%
        mutate(effect = ___ - ___),
    pairwise.t.test(x = ___, g = ___, p.adjust.method = "bonferroni")
)

11.2 Wrap-up

Analysis of Variance, is used to address questions about whether multiple independent groups differ from one another on average. The F statistic is used to summarize how much variability there is between groups versus the amount of variability within groups. We used random permutation to simulate the kinds of data that would occur if the null hypothesis were true. We used simulation as well as a mathematical model to determine whether the observed F statistic is large enough to reject the null hypothesis.