Why Some Embrace Masks and Others Reject Them: An EPPM-Based Mathematical Model

In the context of the COVID‑19 pandemic, this article examines why individuals exhibit divergent behaviors such as wearing masks or refusing them, using the Extended Parallel Processing Model (EPPM) to explain underlying psychological mechanisms.

Extended Parallel Processing Model

The EPPM is a psychological theory that describes how people respond to threats by considering two core factors: perceived threat (severity and susceptibility) and perceived efficacy (response efficacy and self‑efficacy). When both threat and efficacy are high, individuals are most likely to adopt protective measures; high threat with low efficacy leads to fear and inaction; low threat with high efficacy may result in selective compliance.

Mathematical Model

To quantify the EPPM, a simple mathematical model represents perceived threat and perceived efficacy as values between 0 and 1 and defines compliance as a function of these variables. The model distinguishes four scenarios:

High threat + high efficacy → high compliance.

Low threat + low efficacy → low compliance.

High threat + low efficacy → very low compliance due to fear and helplessness.

Applying the model clarifies four behavioral groups:

High threat, high efficacy: strict adherence to measures (mask‑wearing, hand‑washing).

High threat, low efficacy: panic or avoidance, little protective action.

Low threat, high efficacy: selective adoption of measures.

Low threat, low efficacy: minimal or no protective behavior.

Insights

Public‑health communication should focus on increasing confidence in the effectiveness of protective measures while avoiding exaggerated threat messages that could cause fear and disengagement. Tailored strategies for different audience segments—based on their threat and efficacy perceptions—are more effective than one‑size‑fits‑all approaches.

The EPPM framework and its quantitative model can also be applied beyond infectious disease, such as encouraging regular health check‑ups, smoking cessation, weight loss, or disaster preparedness, by adjusting perceived threat and efficacy to promote desired protective behaviors.