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In Chapter 1, site-specifically phosphorylated variants of the oncogene Akt1 were made in Escherichia coli using the orthogonal translation system that enable genetic code expansion with phosphoserine. The differentially phosphorylated variants of Akt1 were used to validate newly predicted Akt1 substrates. The predicted target sites of the peptide substrates were synthesized and subjected to in vitro kinase assays to quantify the activity of each Akt1 phosphorylated variant towards the predicted peptide. A previously uncharacterized kinase-substrate interaction between Akt1 and a peptide derived from RAB11 Family Interacting Protein 2 (RAB11FIP2) was validated in vitro. Chapter 2 describes the preliminary development of a novel orthogonal translation system for Bacillus subtilis. The work presented outlines the design process: from selection of the components to the generation of an all-in-one plasmid containing the orthogonal translation system. The work demonstrates stable integration of the orthogonal translation system into the B. subtilis genome.

Developmental studies show that it takes longer for children learning spoken languages to acquire viewpointdependent spatial relations (e.g., left-right, front-behind), compared to ones that are not viewpoint-dependent (e.g., in, on, under). The current study investigates how children learn to express viewpoint-dependent relations in a sign language where depicted spatial relations can be communicated in an analogue manner in the space in front of the body or by using body-anchored signs (e.g., tapping the right and left hand/arm to mean left and right). Our results indicate that the visual-spatial modality might have a facilitating effect on learning to express these spatial relations (especially in encoding of left-right) in a sign language (i.e., Turkish Sign Language) compared to a spoken language (i.e., Turkish).

Contains fulltext : 131350.pdf (author's version ) (Open Access) Cognitive Science Society, 23 juli 2014

Contains fulltext : 131342.pdf (Publisher’s version ) (Open Access) COGSCI, 23 juli 2014

Early studies investigating sign language acquisition claimed that signs whose structures are motivated by the form of their referent (iconic) are not favoured in language development. However, recent work has shown that the first signs in deaf children’s lexicon are iconic. In this paper we go a step further and ask whether different types of iconicity modulate learning sign-referent links. Results from a picture description task indicate that children and adults used signs with two possible variants differentially. While children signing to adults favoured variants that map onto actions associated with a referent (action signs), adults signing to another adult produced variants that map onto objects’ perceptual features (perceptual signs). Parents interacting with children used more action variants than signers in adult-adult interactions. These results are in line with claims that language development is tightly linked to motor experience and that iconicity can be a communicative strategy in parental input.

In conversation, speakers are likely to refer to the same objects more than once. These repeated references are reduced with respect to their initial counterparts, both in speech and gestures. In this paper we investigate the effect of cognitive load on the reduction of multimodal referring expressions. We report an experiment in which native speakers of Dutch engaged in a director-matcher task where repeated references were elicited, and a time constraint was imposed in order to increase the load. Our results show that articulatory, lexical, semantic, and gestural reduction took place irrespective of the cognitive demands. Nevertheless, we found that cognitive load moderated the extent to which these utterances were reduced, with reduction being less pronounced for speakers experiencing higher load. A subsequent perception experiment revealed that speakers with an increased load produced referring expressions that proved more informative to naïve listeners.

Dual or multiple systems approaches are ubiquitous in cognitive science, with examples in memory, perception, categorization, cognitive development, and many other fields. Dynamical systems models with multiple stable states or modes of behavior are also increasingly used in explaining cognitive phenomena. Catastrophe theory provides a formal framework for studying the dynamics of switching between two qualitatively distinct modes of behavior. Here we present a parametric approach to testing specific predictions about the dynamics of such switches that follow from catastrophe theory. These so-called catastrophe flags are bimodality, divergence, and hysteresis. We show how these three flags can be tested using (constrained) mixture and hidden Markov models and provide an example of each using three different data sets.

One study found that observers retained more information from hand gestures that speakers gazed at, possibly because speaker-gaze shifted observers' attention covertly. Speaker-gaze may thus modulate the role of gestures in communication. One hypothesized communicative function of gestures, and specifically of the inter-personal repetition of gestures, is to facilitate the process of creating common ground (grounding). Therefore, speaker-gaze may also influence the inter-personal repetition of gestures. In an experimental study, we found that participants were more likely to repeat another speaker's gestures if the original speaker gazed at the gestures. Moreover, speaker-gaze was a better predictor of this repetition than participants' own gaze. This supports the hypothesis that speakers' gaze at their gestures leads to covert attention shifts in observers, causing the gestures to be processed differently. Speaker-gaze could therefore be a valuable cue to the processing and production of gestures by artificial systems that interact with humans.

The study of second language acquisition (SLA) is often hindered by substantial variability in the background of learners, their learning process and the input they receive. This diversity often makes it difficult to isolate specific learning factors and study their impact on L2 development. We present a computational study of SLA as an alternative methodological approach. By applying a usage-based computational model of construction learning on bilingual (German and English) input data, we analyze various learning variables in isolation. In particular, we investigate three factors: ratio between the amount of L1 and L2 input, age of L2 onset, and L2 frequency distribution. Our results are in line with experimental findings on the facilitatory effect of lower L1/L2 ratio and balanced L2 frequency distribution. We found no negative effect of later age of L2 onset on proficiency, which might be due to positive cross-linguistic transfer between German and English constructions.