What do you mean with “direction”? Local and global cues to biological motion perception in pigeons

AbstractBiological motion point-light displays are a rich and versatile instrument to study perceptual organization. Humans are able to retrieve information from biological motion through at least two different channels: The global articulated structure as revealed by the non-rigid, yet highly constrained deformation of the dot pattern, and the characteristics of local motion trajectories of individual dots. Here, we tested eight pigeons on a task in which they had to discriminate a left-facing from a right-facing biological motion point-light figure. Since the two stimuli were mirror-flipped versions of each other, we were not sure if the birds would be able to solve the task at all. However, all birds learned the discrimination quickly and performed at high accuracy. We then challenged them with a number of test trials introduced into the sequence of the normal training trials. Tested on backwards moving walkers, the majority of the birds indicated that they used local motion cues to solve the training task, while the remaining birds obviously used global, configural cues. Testing the pigeons on different versions of scrambled biological motion confirmed that each individual bird had made a clear decision for one of the two potentially available strategies. While we confirm a previously described local precedence in processing visual patterns, the fact that some birds used global features suggests that even the birds who relied on local cues probably dispose of the perceptual abilities to use global structure, but “chose” to not use them

Tenzing and the importance of tool development for research efficiency

The way science is done is changing. While some tools are facilitating this change, others lag behind. The resulting mismatch between tools and researchers' workflows can be inefficient and delay the progress of research. As an example, information about the people associated with a published journal article was traditionally handled manually and unsystematically. However, as large-scale collaboration, sometimes referred to as “team science,” is now common, a more structured and easy-to-automate approach to managing meta-data is required. In this paper we describe how the latest version of tenzing (A.O. Holcombe et al., Documenting contributions to scholarly articles using CRediT and tenzing, PLOS One 15(12) (2020)) helps researchers collect and structure contributor information efficiently and without frustration. Using tenzing as an example, we discuss the importance of efficient tools in reforming science and our experience with tool development as researchers.</p

Normalized power priors always discount historical data

Power priors are used for incorporating historical data in Bayesian analyses by taking the likelihood of the historical data raised to the power α as the prior distribution for the model parameters. The power parameter α is typically unknown and assigned a prior distribution, most commonly a beta distribution. Here, we give a novel theoretical result on the resulting marginal posterior distribution of α in case of the normal and binomial model. Counterintuitively, when the current data perfectly mirror the historical data and the sample sizes from both data sets become arbitrarily large, the marginal posterior of α does not converge to a point mass at α=1 but approaches a distribution that hardly differs from the prior. The result implies that a complete pooling of historical and current data is impossible if a power prior with beta prior for α is used

The Role of Mesotocin on Social Bonding in Pinyon Jays

The neuropeptide oxytocin influences mammalian social bonding by facilitating the building and maintenance of parental, sexual, and same‐sex social relationships. However, we do not know whether the function of the avian homologue mesotocin is evolutionarily conserved across birds. While it does influence avian prosocial behavior, mesotocin\u27s role in avian social bonding remains unclear. Here, we investigated whether mesotocin regulates the formation and maintenance of same‐sex social bonding in pinyon jays (Gymnorhinus cyanocephalus), a member of the crow family. We formed squads of four individually housed birds. In the first, “pair‐formation” phase of the experiment, we repeatedly placed pairs of birds from within the squad together in a cage for short periods of time. Prior to entering the cage, we intranasally administered one of three hormone solutions to both members of the pair: mesotocin, oxytocin antagonist, or saline. Pairs received repeated sessions with administration of the same hormone. In the second, “pair‐maintenance” phase of the experiment, all four members of the squad were placed together in a large cage, and no hormones were administered. For both phases, we measured the physical proximity between pairs as our proxy for social bonding. We found that, compared with saline, administering mesotocin or oxytocin antagonist did not result in different proximities in either the pair‐formation or pair‐maintenance phase of the experiment. Therefore, at the dosages and time frames used here, exogenously introduced mesotocin did not influence same‐sex social bond formation or maintenance. Like oxytocin in mammals, mesotocin regulates avian prosocial behavior; however, unlike oxytocin, we do not have evidence that mesotocin regulates social bonds in birds

Understanding the nature of "superhard graphite"

Numerous experiments showed that on cold compression graphite transforms into a new superhard and transparent allotrope. Several structures with different topologies have been proposed for this phase. While experimental data are consistent with these models, the only way to solve this puzzle is to find which structure is kinetically easiest to form. Using state-of-the-art molecular-dynamics transition path sampling simulations, we investigate kinetic pathways of the pressure-induced transformation of graphite to various superhard candidate structures. Unlike hitherto applied methods for elucidating nature of superhard graphite, transition path sampling realistically models nucleation events necessary for physically meaningful transformation kinetics. We demonstrate that nucleation mechanism and kinetics lead to $M$-carbon as the final product. $W$-carbon, initially competitor to $M$-carbon, is ruled out by phase growth. Bct-C$_4$ structure is not expected to be produced by cold compression due to less probable nucleation and higher barrier of formation

Ultrahard carbon film from epitaxial two-layer graphene

Atomically thin graphene exhibits fascinating mechanical properties, although its hardness and transverse stiffness are inferior to those of diamond. To date, there hasn't been any practical demonstration of the transformation of multi-layer graphene into diamond-like ultra-hard structures. Here we show that at room temperature and after nano-indentation, two-layer graphene on SiC(0001) exhibits a transverse stiffness and hardness comparable to diamond, resisting to perforation with a diamond indenter, and showing a reversible drop in electrical conductivity upon indentation. Density functional theory calculations suggest that upon compression, the two-layer graphene film transforms into a diamond-like film, producing both elastic deformations and sp2-to-sp3 chemical changes. Experiments and calculations show that this reversible phase change is not observed for a single buffer layer on SiC or graphene films thicker than 3 to 5 layers. Indeed, calculations show that whereas in two-layer graphene layer-stacking configuration controls the conformation of the diamond-like film, in a multilayer film it hinders the phase transformation.Comment: Published online on Nature Nanotechnology on December 18, 201

Comprehensive Analysis of Transcript Start Sites in Ly49 Genes Reveals an Unexpected Relationship with Gene Function and a Lack Of Upstream Promoters

Comprehensive analysis of the transcription start sites of the Ly49 genes of C57BL/6 mice using the oligo-capping 5′-RACE technique revealed that the genes encoding the “missing self” inhibitory receptors, Ly49A, C, G, and I, were transcribed from multiple broad regions in exon 1, in the intron1/exon2 region, and upstream of exon -1b. Ly49E was also transcribed in this manner, and uniquely showed a transcriptional shift from exon1 to exon 2 when NK cells were activated in vitro with IL2. Remarkably, a large proportion of Ly49E transcripts was then initiated from downstream of the translational start codon. By contrast, the genes encoding Ly49B and Q in myeloid cells, the activating Ly49D and H receptors in NK cells, and Ly49F in activated T cells, were predominantly transcribed from a conserved site in a pyrimidine-rich region upstream of exon 1. An ∼200 bp fragment from upstream of the Ly49B start site displayed tissue-specific promoter activity in dendritic cell lines, but the corresponding upstream fragments from all other Ly49 genes lacked detectable tissue-specific promoter activity. In particular, none displayed any significant activity in a newly developed adult NK cell line that expressed multiple Ly49 receptors. Similarly, no promoter activity could be found in fragments upstream of intron1/exon2. Collectively, these findings reveal a previously unrecognized relationship between the pattern of transcription and the expression/function of Ly49 receptors, and indicate that transcription of the Ly49 genes expressed in lymphoid cells is achieved in a manner that does not require classical upstream promoters