NEW ORLEANS, Jan. 23 (UPI) -- Sleep deprivation can leave couples "too tired to say thanks," and lack of gratitude can make partners feel taken for granted, U.S. researchers say.

University of California, Berkeley, psychologist Amie Gordon and lead investigator Berkeley psychologist Serena Chen said the findings shed new light on the emotional interdependence of sleep partners, offering compelling evidence that a bad night's sleep leaves people less attuned to their partner's moods and sensitivities. For many couples, nighttime can turn into a battleground due to loud snoring, sheet-tugging or one partner tapping on a laptop while the other tosses and turns, Gordon said.

"You may have slept like a baby, but if your partner didn't, you'll probably both end up grouchy," Gordon said in a statement.

Gordon noted many people claim to be too busy to sleep, even priding themselves on how few hours of slumber they can get by on. The observation inspired her, in part, to study how a lack of sleep might be affecting love lives.

More than 60 couples ages 18-56 participated in each of Gordon's studies. In one experiment, participants kept a diary of their sleep patterns and how a good or bad night's rest affected their appreciation of their significant other.

In another experiment, the couples were videotaped engaged in problem-solving tasks. Those who had slept badly the night before showed less appreciation for their partner.

Overall, the results showed poor sleepers had a harder time counting their blessings and valuing their partners, Gordon said.

The findings were presented at the annual meeting of the Society for Personality and Social Psychology in New Orleans.