**Background.**
Recent research investigated the impact of the current cognitive state, especially of cognitive effort and depletion, on the strength of a chosen password. However, that research was open to alternative explanations that fear or stress of participants could have affected the result.
**Aim.**
We investigate the effect of incidental fear and stress on the measured strength of a chosen password.
**Method.**
We conducted two experiments with within-subject designs measuring the Zxcvbn log10 number of guesses as strength of chosen passwords as dependent variable. In both experiments, participants were signed up to a site holding their personal data and, for the second run a day later, asked under a security incident pretext to change their password.
1. **Fear.** $N_F = 34$ participants were exposed to standardized fear and happiness stimulus videos in random order. The Zxcvbn password
strength was compared across groups and the correlation with
reported fear and happiness evaluated.
2. **Stress.** $N_S = 50$ participants were either exposed to a battery of standard stress tasks or left in a control condition in random
order.
In addition, we evaluated the interaction between the stress
condition and cognitive effort as measured with the NASA Talk Load
Index (TLX).
**Results.**
While our fear and stress manipulations were highly successful with large effect sizes, we did not observe a statistically significant difference in mean Zxcvbn password strengths on fear(Hedges' $g_{av} = -0.11$, 95\% CI $[-0.45, 0.23]$) or stress (and control group, Hedges' $g_{av} = 0.01$, 95\% CI $[-0.31, 0.33]$). However, we found a statistically significant cross-over interaction of stress and TLX mental demand.
**Conclusions.**
While having observed negligible effect size estimates for incidental fear or stress, we offer evidence towards the interaction between stress and cognitive effort that vouches for further investigation. Our estimation of investigated effects and our network meta analysis including previously investigated effects offer insights in how cognitive effort, fear and stress all influence the user's password choice.
**Acknowledgement.**
This work was supported by the ERC Starting Grant Confidentiality-Preserving Security Assurance (CASCAde, GA no 716980).
