Stone, Rudd, Ragozzino, and Gold (1992) investigated the role that glucose plays in memory. Mice were raised with a 12 hour light-on/light-off cycle, starting at 6:00 AM. During training mice were placed in the lighted half of an experimental box and given foot shock when they moved into the dark half. The mice quickly learned to stay in the lighted half. The day/night cycle was then advanced by 4 hours for all mice, which is known to interfere with memory of the original training. Three days later mice were retested 30 minutes after being injected with 0, 1, 10, 100, 250, or 500 mg/kg of sucrose. The purpose was to see whether sucrose would reduce the disruptive effects of changing the diurnal cycle, and whether different doses would have different effects. Data that have been generated to loosely mimic the results of Stone et al. are given below, where the dependent variable is the latency to enter the dark chamber.
a. Plot these data using both the actual dosage, and the values 1, 2, 3, 4, 5, 6 as the values of X.
b. Run a trend analysis using SPSS Oneway, if available, with the actual dosage as the independent variable.
c. Repeat part b) using the 1, 2, 3, 4, 5, 6 coding as the independent variable.
d. Interpret your results. How might these results have something to say to students who stay up all night studying for an exam?
e. Why might you, or Stone et al., prefer one coding system over another?