304 research outputs found
Continuous versus discrete quantity discrimination in dune snail (Mollusca: Gastropoda) seeking thermal refuges
The ability of invertebrates to discriminate quantities is poorly studied, and it is unknown whether other phyla possess the same richness and sophistication of quantification mechanisms observed in vertebrates. The dune snail, Theba pisana, occupies a harsh habitat characterised by sparse vegetation and diurnal soil temperatures well above the thermal tolerance of this species. To survive, a snail must locate and climb one of the rare tall herbs each dawn and spend the daytime hours in an elevated refuge position. Based on their ecology, we predicted that dune snails would prefer larger to smaller groups of refuges. We simulated shelter choice under controlled laboratory conditions. Snails’ acuity in discriminating quantity of shelters was comparable to that of mammals and birds, reaching the 4 versus 5 item discrimination, suggesting that natural selection could drive the evolution of advanced cognitive abilities even in small-brained animals if these functions have a high survival value. In a subsequent series of experiments, we investigated whether snails used numerical information or based their decisions upon continuous quantities, such as cumulative surface, density or convex hull, which co-varies with number. Though our results tend to underplay the role of these continuous cues, behavioural data alone are insufficient to determine if dune snails were using numerical information, leaving open the question of whether gastropod molluscans possess elementary abilities for numerical processing
Dynamic Data Selection for Neural Machine Translation
Intelligent selection of training data has proven a successful technique to
simultaneously increase training efficiency and translation performance for
phrase-based machine translation (PBMT). With the recent increase in popularity
of neural machine translation (NMT), we explore in this paper to what extent
and how NMT can also benefit from data selection. While state-of-the-art data
selection (Axelrod et al., 2011) consistently performs well for PBMT, we show
that gains are substantially lower for NMT. Next, we introduce dynamic data
selection for NMT, a method in which we vary the selected subset of training
data between different training epochs. Our experiments show that the best
results are achieved when applying a technique we call gradual fine-tuning,
with improvements up to +2.6 BLEU over the original data selection approach and
up to +3.1 BLEU over a general baseline.Comment: Accepted at EMNLP201
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