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Microtubules are polar, dynamic filaments fundamental to many cellular processes. In vitro reconstitution approaches with purified tubulin are essential to elucidate different aspects of microtubule behavior. To date, deriving data from fluorescence microscopy images by manually creating and analyzing kymographs is still commonplace. Here, we present MTrack, implemented as a plug-in for the open-source platform Fiji, which automatically identifies and tracks dynamic microtubules with sub-pixel resolution using advanced objection recognition. MTrack provides automatic data interpretation yielding relevant parameters of microtubule dynamic instability together with population statistics. The application of our software produces unbiased and comparable quantitative datasets in a fully automated fashion. This helps the experimentalist to achieve higher reproducibility at higher throughput on a user-friendly platform. We use simulated data and real data to benchmark our algorithm and show that it reliably detects, tracks, and analyzes dynamic microtubules and achieves sub-pixel precision even at low signal-to-noise ratios.

Replicative DNA polymerases misincorporate ribonucleoside triphosphates (rNTPs) into DNA approximately once every 2,000 base pairs synthesized. Ribonucleotide excision repair (RER) removes ribonucleoside monophosphates (rNMPs) from genomic DNA, replacing the error with the appropriate deoxyribonucleoside triphosphate (dNTP). Ribonucleotides represent a major threat to genome integrity with the potential to cause strand breaks. Furthermore, it has been shown in the bacterium Bacillus subtilis that loss of RER increases spontaneous mutagenesis. Despite the high rNTP error rate and the effect on genome integrity, the mechanism underlying mutagenesis in RER-deficient bacterial cells remains unknown. We performed mutation accumulation lines and genome-wide mutational profiling of B. subtilis lacking RNase HII, the enzyme that incises at single rNMP residues initiating RER. We show that loss of RER in B. subtilis causes strand- and sequence-context–dependent GC → AT transitions. Using purified proteins, we show that the replicative polymerase DnaE is mutagenic within the sequence context identified in RER-deficient cells. We also found that DnaE does not perform strand displacement synthesis. Given the use of nucleotide excision repair (NER) as a backup pathway for RER in RNase HII-deficient cells and the known mutagenic profile of DnaE, we propose that misincorporated ribonucleotides are removed by NER followed by error-prone resynthesis with DnaE.

Previous findings have been equivocal as to whether the postevent misinformation effect on eyewitness memory is reduced by warnings presented after the misinformation (postwarnings). In the present research, social postwarnings, which characterize the postevent source as a low-credibility individual, diminished the misinformation effect in both cued recall and recognition tests. Discrediting the source as being either untrustworthy or incompetent was effective (Experiment 1). Also, postwarned participants rated reality characteristics of their memories more accurately than did participants receiving no or high-credibility information about the postevent source (Experiment 2). A social postwarning yielded the same results as an explicit source-monitoring appeal and led to longer response times for postevent items, relative to a no-warning condition (Experiments 3 and 4). The findings suggest that the reduced misinformation effect was due to more thorough monitoring of memory characteristics by postwarned participants, rather than to a stricter response criterion or to enhanced event memory.

To test our hypothesis that conversations can contribute to the formation of collective memory, we asked participants to study stories and to recall them individually (pregroup recollection), then as a group (group recounting), and then once again individually (postgroup recollection). One way that postgroup collective memories can be formed under these circumstances is if unshared pregroup recollections in the group recounting influences others' postgroup recollections. In the present research, we explored (using tests of recall and recognition) whether the presence of a dominant narrator can facilitate the emergence of unshared pregroup recollections in a group recounting and whether this emergence is associated with changes in postgroup recollections. We argue that the formation of a collective memory through conversation is not inevitable but is limited by cognitive factors, such as conditions for social contagion, and by situational factors, such as the presence of a narrator.

Frederick Bartlett's Remembering: A Study in Experimental and Social Psychology offered a radical alternative to the century-old notion that memory was like a storehouse. Bartlett insisted that memories were not stored away, but were reconstructed on the run, with new rendering emerging with each act of reconstruction. As a result, psychologists should study not memory, but remembering, and focus on the social contexts in which remembering takes place. Recent work on deep learning and reconsolidation has provided substantial support for Bartlett's approach.

A few days ago, i signed a petition calling for the establishment of archives for oral histories of the COVID-19 pandemic. The hope was that, with the establishment of these archives, as well as the constructions of memorials and the establishment of various social practices, society might \"never forget\" the pandemic. Although I signed the petition, I am not very sanguine about the long-term prospect of this endeavor, as all the evidence suggests that we will forget.

As Nicholas Humphrey nicely documents in his erudite essay in this volume, the notion that there is much that is unknowable about humanity has been around for a long time. Of course, people know a great deal about human nature just by observing it. Even infants know implicitly that they will fall off a visual cliff if they crawl a few more feet. Moreover, by the time they are six years old, they can articulate this information. The past 100 to 150 years of scientific psychological study have increased the body of knowledge, adding significantly to what the layperson knows—and, in some instances, correcting this knowledge. Experimental psychologists now know much more about human behavior and cognition than they did at the turn of the last century. They can identify the neurons that light up when exposed to a red color chip, and they can describe in some detail the mechanisms involved in color perception. Psychological models, as well as neurological ones, cover a wide range of topics, from decisionmaking to sensory perception, remembering to operant conditioning. Given this scientific progress, one might expect a level of resistance to the claims of unknowability animating the writers Humphrey quotes. At the very least, there might be some hesitancy about the validity of the claims. However, as the three essays in this section of the conference on unknowability make clear, many aspects of human behavior and cognition will remain unknowable—not just now but forever. The challenge for anyone considering unknowability is not to state what is unknown at present. A great deal is currently unknown about human behavior and cognition. Rather, the challenge is to outline what one will never know, no matter how much progress is made. Prognostication is, of course, always a risky affair, but one can stake out principles upon which to make claims about unknowability. The three authors do just this. They each adopt a distinctive perspective. Fiske is concerned with what one can never know about one's self and the factors that might mediate such knowledge—or lack of knowledge; Humphrey struggles with the parameters of what one person can know about another person; and McGoey explores how what I call social frames limit what one can know.