The environment has a temporal structure, and knowing when a stimulus will appear translates into increased perceptual performance. Here we investigated how the human brain exploits temporal regularity in stimulus sequences for perception. We find that the timing of stimuli that occasionally deviate from a regularly paced sequence is perceptually distorted. Stimuli presented earlier than expected are perceptually delayed, whereas stimuli presented on time and later than expected are perceptually accelerated. This result suggests that the brain regularizes slightly deviant stimuli with an asymmetry that leads to the perceptual acceleration of expected stimuli. We present a Bayesian model for the combination of dynamically-updated expectations, in the form of a priori probability of encountering future stimuli, with incoming sensory information. The asymmetries in the results are accounted for by the asymmetries in the distributions involved in the computational process.
An isochronous sequence is a series of repeating events with the same inter-onsetinterval. A common finding, is that as a the length of a sequence increases, so does temporal sensitivity to irregularities -that is, the detection of deviations from isochrony is better with a longer sequence. Several theoretical accounts exist in the literature as to how the brain processes sequences for the detection of irregularities, yet there remains to be a systematic comparison of the predictions that such accounts make. To compare the predictions of these accounts, we asked participants to report whether the last stimulus of a regularly-timed sequence appeared 'earlier' or 'later' than expected. Such task allowed us to separately analyse bias and performance.Sequences lengths (3, 4, 5 or 6 beeps) were either randomly interleaved or presented in separate blocks. We replicate previous findings showing that temporal sensitivity increases with longer sequence in the interleaved condition but not in the blocked condition (where performance is higher overall). Results also indicate that there is a consistent bias in reporting whether the last stimulus is isochronous (irrespectively of how many stimuli the sequence is composed of). Such result is consistent with a perceptual acceleration of stimuli embedded in isochronous sequences. From the comparison of the models' predictions we determine that the improvement in sensitivity is best captured by an averaging of successive estimates, but with an element that limits performance improvement below statistical optimality. None of the models considered, however, provides an exhaustive explanation for the pattern of results found.3
A commercial synthesis of the antiglaucoma agent, travoprost 2, is described. A total of 22 synthetic steps are required to provide the single enantiomer prostanoid, with the longest linear sequence being 16 steps from 3-hydroxybenzotrifluoride. The route is based upon a cuprate-mediated coupling of the single enantiomer vinyl iodide 13 and the tricyclic ketone 5, of high stereochemical purity, to yield the single isomer bicyclic ketone 15. A Baeyer-Villiger oxidation provides the lactone 16 as a crystalline solid, thus limiting the need for chromatographic purification. DIBAL-H reduction, Wittig reaction, esterification, and silyl group deprotection complete the synthesis of travoprost.
The moral foundations theory (MFT) is an influential multifactorial model that posits how decision-making in the moral context originates from a set of six intuitive moral foundations: care, fairness, authority, loyalty, purity, and liberty. The established measure of these foundations-the Moral Foundations Questionnaire (MFQ)-has been used extensively in a range of empirical projects. However, recent analyses of its factor structure and the internal consistency of each of the foundation clusters have called its validity into question. In this paper, data from a large sample of British voters were used to re-examine the factor structure of the MFQ. As opposed to a 6-factor structure, only three meaningful clusters emerged in an exploratory principal factors analysis (Study 1; N = 428): traditionalism, compassion, and liberty. This structure was broadly confirmed in an independent sample (Study 2; N = 322). Concurrent validity was established via correlations with measures of 'social change' and 'systemic inequality' insecurities (Study 1) and voting behaviour and preferences (Study 2). Significant differences on each of the three factors of the revised MFQ (MFQ-r) were observed between the voters of different political parties (Study 1) and sides of the Brexit issue (Study 2). Implications for moral foundations theory and its measurement are discussed.Moral foundations theory (MFT; Haidt & Joseph, 2004) is a theoretical framework of moral decision-making. It has been applied to a range of areas of study, such as self-identified political ideology (
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