The Similarity And Difference Between Procrastination And Impulsivity Based On The Structural And Functional MRI Study

Procrastination is a prevalent problematic behavior that brings serious consequences,such as lower levels of health,wealth,and well-being.Therefore,it is important to figure out the impacting factors or causes of procrastination.Procrastination is the phenomenon that individuals are to voluntarily delay an intended course of action despite expecting to be worse off for the delay.Previous research has explored the impact of task characteristics,individual difference,outcomes and demographics on procrastination by behavioral study,behavioral genetics study and cognitive neuroscience study.They tried to explain the nature of procrastination from psychoanalysis,behaviorism and cognitive psychology perspective.It was found that impulsivity was closely related to procrastination and they share the considerable genetic variation(100%).However,little is known about the neural substrates underlying the relationship between procrastination and impulsivity.In the study 1,we have recruited two samples and explored the common neural structural basis of the procrastination and impulsivity using the VBM(Voxel-based morphometry)method in sample 1.In the study 2,we have explored the different neural functional basis of procrastination and impulsivity.In the study 1,we used the GPS(General Procrastination Scale)and BIS(The Barratt impulsiveness scale version 11)to measure the procrastination and impulsivity of participants(two samples,85 subjects in sample 1 and 84 subjects in sample 2)respectively.In the sample 1,we explored the behavioral correlation of procrastination and impulsivity.In line with previous studies,the results showed a significantly positive correlation between procrastination and impulsivity(r = 0.69,p < 0.001).Then,we explored the similarity of measurement of GPS and BIS by factor analysis.The result showed that the items of one component are from the same measurement,GPS or BIS.That means that the GPS and BIS have the low level of similarity and overlapping.We can continue using the two scales to measure two behaviors or traits and the high level of behavioral correlation may not result from the similarity of measurement.Finally,we explored the neural structural basis of procrastination and impulsivity by using the VBM method.The results showed that both procrastination and impulsivity are significantly related to the gray matter volume(GMV)of the overlapping dorsal prefrontal cortex(DLPFC).In the sample 2,in order to avoid the argument circular and to test our result in the sample 1,we conducted the mediation analysis.The results showed that the effect of the GMV of overlapping DLPFC on procrastination was mediated by impulsivity.That indicated that the GMV of overlapping DLPFC has impacted the impulsivity directly,but that of procrastination indirectly by the mediator impulsivity.This finding provides the supporting evident for the idea that the procrastination is the byproduct of impulsivity.In the study 2,we mainly explored the difference between procrastination and impulsivity based on the brain neural function.The study 1 has indicated the similarity of neural structural basis of procrastination and impulsivity.As we all know,the neural structure is the fundamental part of neural function.However,we cannot infer the similarity of brain neural function only by the result of the similarity of brain neural structure.Thus,we used the same measurement of GPS and BIS to get the index of procrastination and impulsivity.Then,we conduct the whole brain correlation analysis.The results showed that(1)procrastination scores were significantly negatively correlated with the ALFF of the left insula;impulsivity was significantly positively related with the ALFF of left caudate(2)Procrastination was significantly positively correlated with the rest functional connectivity of the left insula and the right lingual gyrus.Impulsivity was significantly negatively correlated with the rest functional connectivity of left caudate and the right precentral gyrus.To sum up,(1)procrastination and impulsivity share the common brain neural structural basis in the self-control related DLPFC.Thus,the high level of correlation between procrastination and impulsivity may result from the overlapping DLPFC and the lack of self-control ability.However,the influence of the DLPFC on procrastination or impulsivity is different.For the impulsivity,that is direct.But for the procrastination,that is indirect and that needs the mediator impulsivity.To some degree,our results provide another new evidence to support the idea that the procrastination is the byproduct of impulsivity.(2)There was much difference between procrastination and impulsivity based the brain neural function.Procrastination had the close relationship with insula,but impulsivity has the close relationship with the caudate.That indicated that the motivation of procrastination is the negative emotion.During the process of pursuing the long-term goals,procrastinators are in negative mood.They want to feel better,but the irrational way of task avoidance,involving indulging the temptation,is chosen.Impulsive individuals yield to the temptation as well,but their behavioral motivation different.Impulsive Individuals do this because of reward sensitivity and they cannot stop not choosing the temptation.