Participants in employer-sponsored retirement plans don’t always understand basic concepts of investing, and that’s keeping them from taking the best advantage of their plans -- contributing more and making more frequent contributions -- according to a survey released by the Guardian Insurance and Annuity Company on Thursday.

Most plan participants (92 percent) are satisfied with their 401(k)s, but they lack an understanding of basic investment concepts, which contributes to lower plan engagement and less successful retirement outcomes, says Guardian.

The survey, "The Guardian Small Plan 401(k) RetireWell Study 2.0: What’s Working and Not Working for Small Plan Participants,” polled 2,000 employees who are participating in a 401(k) or have at least $1,000 in one. Small plans for the survey are defined as employers with 25 or fewer employees.

The survey showed that participants lack a general understanding of some basic investment concepts. Two-thirds of participants who have heard of target date or target risk funds say they do not understand the terms. Seventy-seven percent have heard of vesting but fewer than half of that group say they understand the term completely.

“The RetireWell Study magnifies the importance and expectations plan participants place on their defined contribution plans,” says Douglas Dubitsky, vice president of Guardian Retirement Solutions. “However, our research also shows that most individuals are unprepared to make decisions or take action to optimize their 401(k) plans. This is where education and support can make a significant difference in improving retirement outcomes.”