Odor lateralization test is insensitive to small degrees of intranasal trigeminal activation

Adding a small amount of a trigeminal compound to a selective olfactory odor does not significantly improve lateralization performance. Trigeminal lateralization likely follows an "accumulative" pattern rather than an "all or none" rule. With only 20 trials, the task may lack sensitivity to detect low levels of trigeminal irritation in selective olfactory odors, though it does not rule out trigeminal activation. The odor lateralization task can screen for odors with prominent trigeminal compounds by comparing group-level performance with that of purely olfactory odors. Future studies should use more ideal stimuli (e.g., PEA for olfactory, CO2 for trigeminal) to test the replicability of the results.