Saturday, July 18, 2020

Feynman on utter honesty & scientific integrity: "Cargo Cult Science," 1974

Feynman on utter honesty & scientific integrity: "Cargo Cult Science," 1974. http://calteches.library.caltech.edu/51/2/CargoCult.htm

We have learned a lot from experience about how to handle some of the ways we fool ourselves.  One example: Millikan measured the charge on an electron by an experiment with falling oil drops and got an answer which we now know not to be quite right.  It’s a little bit off, because he had the incorrect value for the viscosity of air.  It’s interesting to look at the history of measurements of the charge of the electron, after Millikan.  If you plot them as a function of time, you find that one is a little bigger than Millikan’s, and the next one’s a little bit bigger than that, and the next one’s a little bit bigger than that, until finally they settle down to a number which is higher.

Why didn’t they discover that the new number was higher right away?  It’s a thing that scientists are ashamed of—this history—because it’s apparent that people did things like this: When they got a number that was too high above Millikan’s, they thought something must be wrong—and they would look for and find a reason why something might be wrong.  When they got a number closer to Millikan’s value they didn’t look so hard.  And so they eliminated the numbers that were too far off, and did other things like that.  We’ve learned those tricks nowadays, and now we don’t have that kind of a disease.

But this long history of learning how to not fool ourselves—of having utter scientific integrity—is, I’m sorry to say, something that we haven’t specifically included in any particular course that I know of.  We just hope you’ve caught on by osmosis.


Effects of Leaving a Covenantal Religion: Those who experienced more push toward disaffiliation, reported decreased current wellness; significant differences in the experiences of disaffiliation between men & women

Engelman, Joel, Glen Milstein, Irvin S. Schonfeld, and Joshua B. Grubbs. 2019. “Leaving a Covenantal Religion: Orthodox Jewish Disaffiliation from an Immigration Psychology Perspective.” PsyArXiv. December 5. doi:10.1080/13674676.2020.1744547

Abstract: This study explored psychological variables associated with disaffiliation from Orthodox Judaism (a covenantal community), and subsequent wellness. A web-based survey (N = 206) assessed factors previously used to study immigrants: push (distress within origin community), pull (toward destination community), and goal attainment. Psychological and emotional wellness, perceived stress, overall health, and loneliness were also assessed. Findings included: 1) strong pull toward opportunities for physical and ideological autonomy; 2) those who experienced more push toward disaffiliation, reported decreased current wellness; 3) goal attainment was associated with increased wellness 4) significant differences in the experiences of disaffiliation between men and women; 5) most who disaffiliated left religion altogether; those who remained religious decreased their participation, few joined non-Jewish faith communities. Results demonstrate that this immigration paradigm can be adapted to advance research on individuals who disaffiliate from covenantal communities.


Initiation of Drug and Alcohol Use and Personality Development During Adolescence: initiation of substance use leads to changes in personality; cocaine and cigarettes were the substances that had the largest impact

Wright, Amanda J., and Joshua J. Jackson. 2020. “What Happens After Your First Time? Initiation of Drug and Alcohol Use and Personality Development During Adolescence.” PsyArXiv. July 18. doi:10.31234/osf.io/gpsj4

Abstract: Personality traits predict both the initiation and continued usage of alcohol and drugs. Less established is if substance use is associated with subsequent changes in personality, especially during the sensitive period of adolescence. We used three novel approaches to disentangle selection and socialization effects to address whether substance use is associated with personality development (impulsivity, sensation-seeking, depression, self-esteem). First, we used a multi-wave longitudinal sample of adolescents (N = 8,303) from the National Longitudinal Study of Youth - Child and Young Adult dataset to study the first use of a controlled substance. Second, we used propensity score weighting to equate users and abstainers on a range of background variables. Third, we investigated changes before, during, and after initiation of substances. Overall, there was unique variability and effects in personality across time for average levels, trajectories, and magnitudes of change both between users and abstainers as well as within users of specific substances. Results suggest that initiation of substance use leads to changes in personality; the specifics of which are largely contingent upon the substance being used. Impulsivity and sensation-seeking were the traits that changed the most while cocaine and cigarettes were the substances that had the largest impact.





Gray Matter Microstructure: While macrostructural features, like brain volume, are mainly genetically influenced, there are genetic & environmental influences on microstructure

Quantifying Genetic and Environmental Influence on Gray Matter Microstructure Using Diffusion MRI. Madhura Baxi, Maria A Di Biase, Amanda E Lyall, Suheyla Cetin-Karayumak, Johanna Seitz, Lipeng Ning, Nikos Makris, Douglas Rosene, Marek Kubicki, Yogesh Rathi. Cerebral Cortex, bhaa174, July 17 2020. https://doi.org/10.1093/cercor/bhaa174

Abstract: Early neuroimaging work in twin studies focused on studying genetic and environmental influence on gray matter macrostructure. However, it is also important to understand how gray matter microstructure is influenced by genes and environment to facilitate future investigations of their influence in mental disorders. Advanced diffusion MRI (dMRI) measures allow more accurate assessment of gray matter microstructure compared with conventional diffusion tensor measures. To understand genetic and environmental influence on gray matter, we used diffusion and structural MRI data from a large twin and sibling study (N = 840) and computed advanced dMRI measures including return to origin probability (RTOP), which is heavily weighted toward intracellular and intra-axonal restricted spaces, and mean squared displacement (MSD), more heavily weighted to diffusion in extracellular space and large cell bodies in gray matter. We show that while macrostructural features like brain volume are mainly genetically influenced, RTOP and MSD can together tap into both genetic and environmental influence on microstructure.

Keywords: imaging genetics, MSD, non-Gaussian model, RTOP, twin study

Check also Sleep duration over 28 years, cognition, gray matter volume, and white matter microstructure: a prospective cohort study. Jennifer Zitser et al. Sleep, zsz290, January 6 2020. https://www.bipartisanalliance.com/2020/01/no-differences-in-cognitive-or.html
Abstract
Study Objectives: To examine the association between sleep duration trajectories over 28 years and measures of cognition, gray matter volume, and white matter microstructure. We hypothesize that consistently meeting sleep guidelines that recommend at least 7 hours of sleep per night will be associated with better cognition, greater gray matter volumes, higher fractional anisotropy, and lower radial diffusivity values. 
Methods: We studied 613 participants (age 42.3 ± 5.03 years at baseline) who self-reported sleep duration at five time points between 1985 and 2013, and who had cognitive testing and magnetic resonance imaging administered at a single timepoint between 2012 and 2016. We applied latent class growth analysis to estimate membership into trajectory groups based on self-reported sleep duration over time. Analysis of gray matter volumes was carried out using FSL Voxel-Based-Morphometry and white matter microstructure using Tract Based Spatial Statistics. We assessed group differences in cognitive and MRI outcomes using nonparametric permutation testing. 
Results: Latent class growth analysis identified four trajectory groups, with an average sleep duration of 5.4 ± 0.2 hours (5%, N = 29), 6.2 ± 0.3 hours (37%, N = 228), 7.0 ± 0.2 hours (45%, N = 278), and 7.9 ± 0.3 hours (13%, N = 78). No differences in cognition, gray matter, and white matter measures were detected between groups. 
Conclusions: Our null findings suggest that current sleep guidelines that recommend at least 7 hours of sleep per night may not be supported in relation to an association between sleep patterns and cognitive function or brain structure. 
Keywords: aging, cognition, gray matter, sleep, white matter 
Statement of Significance: Up to a third of adults report between 6 and 7 hours of sleep per night, and thus fail to meet sleep guidelines which recommend at least 7 hours of sleep per night. Although extreme short sleep (e.g. ≤5 hours per night) has repeatedly been associated with poor cognitive health, it is currently unclear if such relationships subsist for more moderate short-sleep durations. We found no differences in cognitive or structural MRI measures between groups that reported, on average, 5.4 hours, 6.2 hours, 7.0 hours, and 7.9 hours sleep per night over 5 timepoints spanning 28 years. If replicated with longitudinal markers of cognitive health, such null results could challenge the suitability of current sleep guidelines on cognitive outcomes.