Background
Positive Psychological Interventions (PPIs) are designed to promote wellbeing by targeting positive variables (e.g., gratitude). These interventions range from completing gratitude letters to completing five novel acts of kindness in one day (Lyubomirsky & Layous, 2013). Researchers have argued that PPIs have cognitive mechanisms; specifically, the gratitude letter may produce attentional deployment and cognitive reappraisal (Gross, 1998). We first tested this hypothesis in a pilot study using a 2 (pre-test vs. post-test) by 2 (control vs. gratitude letter) design. The intervention produced no effects in two of three cognitive tasks. However, the participants who completed the gratitude letter recognized negative words faster on a lexical decision task after the intervention than before (ηp2 = .076, p < .001); control participants did not demonstrate this change, p = .207.
Hypotheses/Research Questions
In the main study, we used a fully between-subjects design to investigate the cognitive effects of the gratitude letter.
Sample Characteristics and Sample Size
Participants (n = 150) were undergraduates (Mage = 19.24, SD = 1.89) who predominantly identified as male (46%) and White/European (56.7%).
Design
All participants completed a 15-minute writing task, either composing a gratitude letter or writing about their morning routine. Then, participants completed three cognitive tasks (emotional Stroop task, affective lexical decision task, and affective lexical memory task) in random order.
Results
Contrary to predictions, participants in the gratitude condition did not perform differently than those in the control conditions on any of the tasks, ps > .161.
Scientific Contribution
Although the literature suggests that PPIs affect emotion regulation processes, evidence is lacking regarding their impact on semantic information processing and memory. While our results do not suggest that all PPIs fail to impact semantic information processing and memory, the gratitude letter intervention is unlikely to affect these cognitive processes.