This is a digital, self-guided SSI that teaches adults about tolerating and embracing uncertainty in their life. The SSI is based on five elements: 1. An introduction the concept of neuroplasticity; 2. Testimonials from peers describing beliefs that people's thoughts, feelings, and behaviors are malleable, given the brain's capacity for change; 3. Strategies (from cognitive-behavioral therapy) for applying these principles to participants' lives; 4. Further vignettes by peers describing times when they tolerated or embraced uncertainty; 5. An exercise wherein participants provide advice to fictional peers, using newly-gleaned information about uncertainty,

This is a digital, self-guided SSI that teaches adults about the benefits of maintaining a healthy lifestyle (e.g., proper sleep, diet, exercise), emphasizing recommendations by various bodies (e.g., American Medical Association). It is structurally similar to the uncertainty-focused SSI but is designed to mimic what people would receive in their annual physical with a primary care physician. The goals of this intervention is to encourage participants to identify aspects of a healthy lifestyle, and steps they could take towards a healthier lifestyle. This SSI is designed to control for nonspecific aspects of intervention, including engagement in a computer program, reading and writing exercises, and vignettes from peers.

Digitally/computer administered 30-minute self-guided intervention for adults ages 25-60

The BHS-482 is a four-item self-report scale that will be used to assess hopelessness before and after the experimental intervention (scale assesses hopelessness "right now, in this moment") to determine whether the intervention was effective in eliciting change in a clinically meaningful construct. It has good psychometric properties. Participants will complete the Beck Hopelessness Scale (BHS-4) before and after the intervention as a manipulation check that the single session intervention (SSI) "worked" in the event that the other primary outcomes exhibit resistance to change.

Computational modeling will be used to extract two parameters indicative of behavioral ambiguity aversion (AA) from a risk and ambiguity task completed once before and once after the intervention. This results in two variables per participant: one which indicates categorical AA (i.e., their tendency to choose the unambiguous choice regardless of the amount of ambiguity present) and one which indicates continuous AA (i.e., how the amount of ambiguity influences people's choice).

From EEG data collected during the risk and ambiguity task, event-related potentials (ERPs)-time-locked electroencephalogram signals with millisecond resolution-will be extracted to yield one variable per participant indicating mean brain activity to ambiguous choices. Pilot data and small prior studies have consistently found an attenuated P300-like component (albeit later than usual, around 350-500ms) to ambiguous relative to unambiguous choices similar to those on this task.