In an experiment, two groups of people were assigned to complete a memory task with either their eyes open, or their eyes closed. Their performance on the memory task was compared to see which group did remembered more words. Memory performance in this experiment is the: dependent variable income measure cross-sectional study O independent variable Older adults experience better emotional regulation and the "positivity effect," while also experiencing declines in attention and memory abilities. This is an example of how development is multidirectional multicausal embedded in historical context O plastic