Employees may be shying away from buying voluntary benefits that they don’t understand.

Researchers at a unit of MetLife Inc., New York, have explored employee attitudes in a survey of 1,204 full-time employees, ages 21 and older, who are working full-time for companies offering benefits.

Although 22% of the employees surveyed said they were happy during their most recent open enrollment period, 49% of the employees said they felt confused or frustrated.

About 37% of the participants said they are confused by annuities, and 31% said they are confused by legal services plans.

Another 25% said they feel confused by descriptions of critical illness insurance.

The researchers found that 79% of the employees said they like Web-based calculators and decision support tools, but only 10% of the employees said their employers offer such tools.

When asked about benefits that employers should add, 56% of the participants named dental insurance, 47% asked for vision insurance and 32% asked for prescription drug plans.