The research I did this summer was a fulfilling experience. I greatly enjoyed working with all members of the Cognitive Psychophysiology Lab. While my study did not come up with anything to say about the use of CNV as a subjective measure of the time duration of a stimuli, I must accept that this is the nature of real research. Sometimes all that research tells us is that further research is needed. This seems to be the case for me. I am in the process of setting up a class slot for indepenter research in psychology with Professor Kieffaber this Fall. I will probably continue to pursue the waveform of interest in my summer study, but will also work on analyzing other ERPs and will get to work with other ongoing studies as well.I greatly appreciate the Charles Center allowing me funding for this foray into undergraduate research!
Discussion of Results
Contrary to expectation, data analysis showed no statistically significant differences between the CNVs generated by stimuli Short Correct and Short Incorrect trials, and by Long Correct and Long Incorrect trials. So the CNV didn’t seem to be a subjective measure. However, from the lack of differences across all trial types, it cannot be said with confidence that the CNV as we have defined it can be used as any kind of measure of duration, subjective or objective.
There does appear to be a difference between the waveforms of the young and old adults, but not in the CNV, the P3 component is probably the culprit, as it is far more pronounced in the younger adults.
One problem with this analysis is the possibility that the reference used by participants may not be the short and long stimuli, but rather the “mean of all the durations experienced”. (Wearden, 2003) Basically, the cut off for what the participant decides is short or long is based on a mean duration that they calculate. This strategy was not expected by the researchers and could account for some of the unexpected results. This possibility will be addressed in further analysis on the data collected in this study.
Another thing of note is the unexpectedly low average accuracy of both groups of participants. Although both groups had an average of 66% accuracy across stimulus durations, some comparisons can be made about the separate groups. Older participants tended to be less accurate with shorter intervals than younger participants. This is consistent with an overestimation of time. Younger Participants tended to be more accurate with longer intervals. This is consistent with an underestimation of time. This pattern suggests that the older participants have a faster running internal clock. If this were the case, their accumulators would be more likely to judge intervals as longer as they would have received more input than would one with a slower internal clock.
I focused on a small part of a larger study being done with the data collected for it. More subjects are being collected, more components will be analyzed, and the CNV will probably be looked into further with some adjustments to our criteria. These adjustments may include, finding the bisection point for each participant, and using that to discriminate short and long, and measuring the CNV on a scalar graph allowing the entirety of the CNV to be included for the longer stimuli.
Data Processing and Finishing Up
This weekend I was able to finish my data processing after brushing up on my MATLAB skills. Prof Kieffaber has updated an add-on to MATLAB called EEGlab and has expedited this process greatly. In this final week I will try to find meaning in the processed data and test to see how good of a subjective measure the CNV was after all. This summer has been a very rewarding experience and I would like to express my gratitude to Prof Kieffaber and masters student Cutter Lindbergh for letting me work with them and to do some data sharing with them as well. I plan to continue to work in the Cognitive Psychophysiology Lab (CPL) in the upcoming fall semester and look forward to continuing to use the skills I have developed this summer.