An embodied approach to language: the role of bodily feedback in discourse processing

Theories of embodied cognition argue that language processing arises not from amodal symbols that redescribe sensorimotor and affective experiences, but from partial simulations (reenactments) of modality-specific states. Recent findings on processing of words and sentences support such a stance emphasizing that the role of the body in the domain of language comprehension should not be overlooked or dismissed. The present research was conducted to extend prior work in two important ways. First, the role of simulation was tested with connected discourse rather than words or sentences presented in isolation. Second, both “online” and “offline” measures of discourse comprehension were taken. In Experiments 1 and 2 participants’ facial postures were manipulated to show that preparing the body for processing of emotion-congruent information improves discourse comprehension. In Experiment 3 the direction of body posture was manipulated to show that implicit properties of simulations, such as spatial dimension or location, are at least somewhat involved in processing of large language segments such as discourse. Finally, in Experiments 4 and 5 participants’ body movement and body posture were manipulated to show that even understanding of language describing metaphorical actions physically impossible to perform involves constructing a sensorimotor simulation of the described event. The major result was that compatibility between embodiment and language strongly modulated performance effectiveness in experiments on simulation of emotion and metaphorical action. The effect of simulation on comprehension of discourse implying spatial dimension was fragile. These findings support an embodied simulation account of cognition suggesting that sensorimotor and affective states are at least partially implicated in “online” and “offline” discourse comprehension.

Electrical characterization of metal-oxide-polymer devices for non-volatile memory applications

The objective of this thesis is to study the properties of resistive switching effect based on bistable resistive memory which is fabricated in the form of Al2O3/polymer diodes and to contribute to the elucidation of resistive switching mechanisms. Resistive memories were characterized using a variety of electrical techniques, including current-voltage measurements, small-signal impedance, and electrical noise based techniques. All the measurements were carried out over a large temperature range. Fast voltage ramps were used to elucidate the dynamic response of the memory to rapid varying electric fields. The temperature dependence of the current provided insight into the role of trapped charges in resistive switching. The analysis of fast current fluctuations using electric noise techniques contributed to the elucidation of the kinetics involved in filament formation/rupture, the filament size and correspondent current capabilities. The results reported in this thesis provide insight into a number of issues namely: (i) The fundamental limitations on the speed of operation of a bi-layer resistive memory are the time and voltage dependences of the switch-on mechanism. (ii) The results explain the wide spread in switching times reported in the literature and the apparently anomalous behaviour of the high conductance state namely the disappearance of the negative differential resistance region at high voltage scan rates which is commonly attributed to a “dead time” phenomenon which had remained elusive since it was first reported in the ‘60s. (iii) Assuming that the current is filamentary, Comsol simulations were performed and used to explain the observed dynamic properties of the current-voltage characteristics. Furthermore, the simulations suggest that filaments can interact with each other. (iv) The current-voltage characteristics have been studied as a function of temperature. The findings indicate that creation and annihilation of filaments is controlled by filling and neutralizing traps localized at the oxide/polymer interface. (v) Resistive switching was also studied in small-molecule OLEDs. It was shown that the degradation that leads to a loss of light output during operation is caused by the presence of a resistive switching layer. A diagnostic tool that predicts premature failure of OLEDs was devised and proposed. Resistive switching is a property of oxides. These layers can grow in a number of devices including, organic light emitting diodes (OLEDs), spin-valve transistors and photovoltaic devices fabricated in different types of material. Under strong electric fields the oxides can undergo dielectric breakdown and become resistive switching layers. Resistive switching strongly modifies the charge injection causing a number of deleterious effects and eventually device failure. In this respect the findings in this thesis are relevant to understand reliability issues in devices across a very broad field.