In their experiment, they played a series of high and low tones while asking subjects to do a simple probabilistic classification task.
In the dual task (DT) case, subjects were also asked to count the number of high pitched tones.
However, subjects were significantly better at identifying cue-associations (a test of declarative knowledge) when trained under ST rather than DT conditions.
A study conducted by Csabi, Benedk, Janacesk, Katona and Nemeth[4] looked at the impairment of declarative and nondeclarative learning when a child is sleep-deprived.
Nondeclarative learning was measured by having children perform an Alternating Serial Reaction Time (ASRT) task.
The study showed that nondeclarative learning was preserved and not affected when sleep-deprived children took the ASRT task.
Research focusing on children has also looked at different ways of utilizing declarative learning when it comes to memorizing tasks.
Backhaus, Hoeckesfeld, Born, Hohagen, and Junghanns [5] conducted a study to see if sleeping after a task enhances declarative learning in children.
In a study conducted by Espin et al.[6] stress, hormones and menstrual cycle phases in women, were tested for their effect on declarative learning in young adults.
The study showed that if women were not exposed to the TSST task before the RAVLT there was an increase of declarative learning and recall when compared to the men.
However, when the participants were exposed to the TSST task before the RAVLT then declarative learning and recall were equal for both men and women.
For the Explicit task participants were told they had to reproduce letter strings according to a set of rules, which they had to determine and would be tested on later.
This shows that adults are using declarative learning when undergoing explicit tasks, such as memorizing formulas for a statistics class.