The City Infant Faces Database: A validated set of infant facial expressions

Adults need to be able to process infants' emotional expressions accurately to respond appropriately and care for infants. However, research on processing of the emotional expressions of infant faces is hampered by the lack of validated stimuli. Although many sets of photographs of adult faces are available to researchers, there are no corresponding sets of photographs of infant faces. We therefore developed and validated a database of infant faces, which is available via e-mail request. Parents were recruited via social media and asked to send photographs of their infant (0-12 months of age) showing positive, negative, and neutral facial expressions. A total of 195 infant faces were obtained and validated. To validate the images, student midwives and nurses (n = 53) and members of the general public (n = 18) rated each image with respect to its facial expression, intensity of expression, clarity of expression, genuineness of expression, and valence. On the basis of these ratings, a total of 154 images with rating agreements of at least 75% were included in the final database. These comprise 60 photographs of positive infant faces, 54 photographs of negative infant faces, and 40 photographs of neutral infant faces. The images have high criterion validity and good test-retest reliability. This database is therefore a useful and valid tool for researchers

Universality of Level Spacing Distributions in Classical Chaos

We suggest that random matrix theory applied to a classical action matrix can be used in classical physics to distinguish chaotic from non-chaotic behavior. We consider the 2-D stadium billiard system as well as the 2-D anharmonic and harmonic oscillator. By unfolding of the spectrum of such matrix we compute the level spacing distribution, the spectral auto-correlation and spectral rigidity. We observe Poissonian behavior in the integrable case and Wignerian behavior in the chaotic case. We present numerical evidence that the action matrix of the stadium billiard displays GOE behavior and give an explanation for it. The findings present evidence for universality of level fluctuations - known from quantum chaos - also to hold in classical physics

Learning multiple rules simultaneously: affixes are more salient than reduplications

Language learners encounter numerous opportunities to learn regularities, but need to decide which of these regularities to learn, because some are not productive in their native language. Here, we present an account of rule learning based on perceptual and memory primitives (Endress, Dehaene-Lambertz, & Mehler, 2007; Endress, Nespor, & Mehler, 2009), suggesting that learners preferentially learn regularities that are more salient to them, and that the pattern of salience reflects the frequency of language features across languages. We contrast this view with previous artificial grammar learning research, which suggests that infants “choose” the regularities they learn based on rational, Bayesian criteria (Frank & Tenenbaum, 2011; Gerken, 2006, 2010). In our experiments, adult participants listened to syllable strings starting with a syllable reduplication and always ending with the same “a!x” syllable, or to syllable strings starting with this “a!x” syllable and ending with the “reduplication.” Both a!xation and reduplication are frequently used for morphological marking across languages. We find three crucial results. First, participants learned both regularities simultaneously. Second, a!xation regularities seemed easier to learn than reduplication regularities. Third, regularities in sequence o↵sets were easier to learn than regularities at sequence onsets. We show that these results are inconsistent with previous Bayesian rule learning models, but mesh well with the perceptual or memory primitives view. Further, we show that the pattern of salience revealed in our experiments reflects the distribution of regularities across languages. Ease of acquisition might thus be one determinant of the frequency of regularities across languages

Primitive computations in speech processing

Previous research suggests that artificial-language learners exposed to quasi-continuous speech can learn that the first and the last syllables of words have to belong to distinct classes (e.g., Endress & Bonatti, 2007; Peña, Bonatti, Nespor, & Mehler, 2002). The mechanisms of these generalizations, however, are debated. Here we show that participants learn such generalizations only when the crucial syllables are in edge positions (i.e., the first and the last), but not when they are in medial positions (i.e., the second and the fourth in pentasyllabic items). In contrast to the generalizations, participants readily perform statistical analyses also in word middles. In analogy to sequential memory, we suggest that participants extract the generalizations using a simple but specific mechanism that encodes the positions of syllables that occur in edges. Simultaneously, they use another mechanism to track the syllable distribution in the speech streams. In contrast to previous accounts, this model explains why the generalizations are faster than the statistical computations, require additional cues, and break down under different conditions, and why they can be performed at all. We also show that that similar edge-based mechanisms may explain many results in artificial-grammar learning and also various linguistic observations

A simple, biologically plausible feature detector for language acquisition

Language has a complex grammatical system we still have to understand computationally and biologically (Hauser et al., 2002; Yang, 2013). However, some evolutionarily ancient mechanisms have been repurposed for grammar (Dehaene & Cohen, 2007; Endress, Cahill, et al., 2009; Endress, Nespor, et al., 2009; Fitch, 2017) so that we can use insight from other taxa into possible circuit level mechanisms of grammar. Drawing upon recent evidence for the importance of disinhibitory circuits across taxa and brain regions (Chevalier & Deniau, 1990; Letzkus et al., 2015; Hangya et al., 2014; Xu et al., 2013; Goddard et al., 2014; Mysore & Knudsen, 2012; Koyama et al., 2016; Koyama & Pujala, 2018), I suggest a simple circuit that explains the acquisition of core grammatical rules used in 85% of the world’s languages (Rubino, 2013): grammatical rules based on sameness/difference relations. This circuit acts as a sameness-detector. Different items are suppressed through inhibition, but presenting two identical items leads to inhibition of inhibition. The items are thus propagated for further processing. This sameness-detector thus acts as a feature detector for a grammatical rule. I suggest that having a set of feature detectors for elementary grammatical rules might make language acquisition feasible based on relatively simple computational mechanisms

First evidence of coherent K+K^{+} meson production in neutrino-nucleus scattering

Neutrino-induced charged-current coherent kaon production, $\nu_{\mu}A\rightarrow\mu^{-}K^{+}A$, is a rare, inelastic electroweak process that brings a $K^+$ on shell and leaves the target nucleus intact in its ground state. This process is significantly lower in rate than neutrino-induced charged-current coherent pion production, because of Cabibbo suppression and a kinematic suppression due to the larger kaon mass. We search for such events in the scintillator tracker of MINERvA by observing the final state $K^+$, $\mu^-$ and no other detector activity, and by using the kinematics of the final state particles to reconstruct the small momentum transfer to the nucleus, which is a model-independent characteristic of coherent scattering. We find the first experimental evidence for the process at $3\sigma$ significance.Comment: added ancillary file with information about the six kaon candidate

Floral uniformity through evolutionary time in a species-rich tree lineage

Changes in floral morphology are expected across evolutionary time and are often promoted as important drivers in angiosperm diversification. Such a statement, however, is in contrast to empirical observations of species-rich lineages that show apparent conservative floral morphologies even under strong selective pressure to change from their environments. Here, we provide quantitative evidence for prolific speciation despite uniform floral morphology in a tropical species-rich tree lineage. We analyse floral disparity in the environmental and phylogenetic context of Myrcia (Myrtaceae), one of the most diverse and abundant tree genera in Neotropical biomes. Variation in floral morphology among Myrcia clades is exceptionally low, even among distantly related species. Discrete floral specialisations do occur, but these are few, present low phylogenetic signal, have no strong correlation with abiotic factors, and do not affect overall macroevolutionary dynamics in the lineage. Results show that floral form and function may be conserved over large evolutionary time scales even in environments full of opportunities for ecological interactions and niche specialisation. Species accumulation in diverse lineages with uniform flowers apparently does not result from shifts in pollination strategies, but from speciation mechanisms that involve other, nonfloral plant traits

Division of labour within flowers: heteranthery, a floral strategy to reconcile contrasting pollen fates

In many nectarless flowering plants, pollen serves as both the carrier of male gametes and as food for pollinators. This can generate an evolutionary conflict if the use of pollen as food by pollinators reduces the number of gametes available for cross-fertilization. Heteranthery, the production of two or more stamen types by individual flowers reduces this conflict by allowing different stamens to specialize in ‘pollinating’ and ‘feeding’ functions. We used experimental studies of Solanum rostratum (Solanaceae) and theoretical models to investigate this ‘division of labour’ hypothesis. Flight cage experiments with pollinating bumble bees (Bombus impatiens) demonstrated that although feeding anthers are preferentially manipulated by bees, pollinating anthers export more pollen to other flowers. Evolutionary stability analysis of a model of pollination by pollen consumers indicated that heteranthery evolves when bees consume more pollen than should optimally be exchanged for visitation services, particularly when pollinators adjust their visitation according to the amount of pollen collected

Biomechanical properties of a buzz-pollinated flower

Approximately half of all bee species use vibrations to remove pollen from plants with diverse floral morphologies. In many buzz-pollinated flowers, these mechanical vibrations generated by bees are transmitted through floral tissues, principally pollen-containing anthers, causing pollen to be ejected from small openings (pores or slits) at the tip of the stamen. Despite the importance of substrate-borne vibrations for both bees and plants, few studies to date have characterised the transmission properties of floral vibrations. In this study, we use contactless laser vibrometry to evaluate the transmission of vibrations in the corolla and anthers of buzz- pollinated flowers of Solanum rostratum, and measured vibrations in three spatial axes. We found that floral vibrations conserve their dominant frequency (300Hz) as they are transmitted throughout the flower. We also found that vibration amplitude at anthers and petals can be up to >400% higher than input amplitude applied at the receptacle at the base of the flowe , and that anthers vibrate with a higher amplitude velocity than petals. Together, these results suggest that vibrations travel differently through floral structures and across different spatial axes. As pollen release is a function of vibration amplitude, we conjecture that bees might benefit from applying vibrations in the axes associated with higher vibration amplification