The role of context in experiments and models of multisensory decision making

Yue Liu was supported by studentship sponsored by the School of Psychology and Neuroscience, University of St Andrews.The availability of signals from multiple senses is often beneficial for perceptual decisions. To study such benefits, models of multisensory decision-making are typically fed with the behavioural performance as measured separately with unisensory component signals. Critically, by doing so, the approach implicitly makes the so-called context invariance assumption, which states that processing of a signal is independent of the experimental context in which it is embedded. However, context invariance is not necessarily true and is difficult to test directly. Here, we aim to assess context invariance indirectly in two testable scenarios. First, to consider the role of stimulus context, we compared unisensory performance in trials that either included a task-irrelevant signal in another modality, or not (unisensory vs. multisensory signal trials). We found that performance was faster but less sensitive in trials that contained a task-irrelevant signal. Hence, stimulus context invariance was violated. Second, to consider the role of instruction context, we compared unisensory performance when participants were asked to detect targets from either one or two modalities (unisensory vs. multisensory instructions). We found that performance was deteriorated in multi- compared to unisensory instructions, which was largely due to modality switch costs in multisensory instructions. Hence, instruction context invariance did not hold either. As performance was variant in both scenarios, context invariance cannot generally assumed to be true. We conclude that models of multisensory decision making should critically consider potential violations of the context invariance assumption as a potentially confounding factor.PostprintPeer reviewe

Single integrated device for optical CDMA code processing in dual-code environment

We report on the design, fabrication and performance of a matching integrated optical CDMA encoder-decoder pair based on holographic Bragg reflector technology. Simultaneous encoding/decoding operation of two multiple wavelength-hopping time-spreading codes was successfully demonstrated and shown to support two error-free OCDMA links at OC-24. A double-pass scheme was employed in the devices to enable the use of longer code length

Random lasing in uniform perovskite thin films

Following the very promising results obtained by the solar cell community, metal halide perovskite materials are increasingly attracting the attention of other optoelectronics researchers, especially for light emission applications. Lasing with both engineered and self-assembled resonator structures, such as microcrystal networks, has now been successfully observed, with the low cost and the simple solution-based process being a particular attraction. The ultimate in simplicity, however, would be to observe lasing from a continuous thin film, which has not been reported yet. Here, we show random lasing action from such a simple perovskite layer. Our lasers work at room temperature; they are deposited on unpatterned glass substrates and they exhibit a minimum threshold value of 10 µJ/cm2. By carefully controlling the solution processing conditions, we can determine whether random lasing occurs or not, using identical precursors. A rather special feature is that some of the films exhibit single and dual mode lasing action, which is rarely observed in random lasers. Our work fully exploits the simplicity of the solution-based process and thereby adds an important capability into the emerging field of perovskite-based light emitters