Manuel J. Blanco

Early, Involuntary Top-Down Guidance of Attention From Working Memory

Four experiments explored the interrelations between working memory, attention, and eye movements. Observers had to identify a tilted line amongst vertical distractors. Each line was surrounded by a colored shape that could be precued by a matching item held in memory. Relative to a neutral baseline, in which no shapes matched the memory item, search was more efficient when the memory cue matched the shape containing the target, and it was less efficient when the cued stimulus contained a distractor. Cuing affected the shortest reaction times and the first saccade in search. The effect occurred even when the memory cue was always invalid but not when the cue did not have to be held in memory. There was also no evidence for priming effects between consecutive trials. The results suggest that there can be early, involuntary top-down directing of attention to a stimulus matching the contents of working memory.

Spatial attention and object-based attention: a comparison within a single task.

There is now much experimental evidence supporting the idea that visual attention can be deployed in at least two ways: one space-based and other object-based. However, it is not clear whether space- and object-based attention work in an integrated way within the visual system. In this article, we present two experiments in which we compare both components of attention within a cueing paradigm. Participants had to discriminate the orientation of a line that appeared within one of four moving circles, differing in colour. A cue appearing close to one of the four circles indicated the location or circle where the target stimulus was likely to appear. Spatial and object cueing effects were observed: responses were faster when target appeared either at the precued location or within the precued object. In addition, the object-cueing effect occurred only when the cue was spatially invalid and not when it was spatially valid. These results suggest that object- and space-based attention interact, with selection by location being primary over object-based selection.

Spanish Norms for the Harvard Group Scale of Hypnotic Susceptibility, Form A

The results of administering the Harvard Group Scale of Hypnotic Susceptibility, Form A (HGSHS:A) of Shor and E. Orne (1962) to a Spanish sample are on the whole consistent with those results obtained in other normative studies, especially Bongartzs work with a German sample, and they confirm HGSHS:As usefulness in non-Anglophone countries. The Spanish HGSHS:As reliability and validity remain within the limits reported for other locales, but there are certain discrepancies with respect to the difficulty of two HGSHS:A items.

On the independence of visual awareness and metacognition: a signal detection theoretic analysis.

Classically, visual awareness and metacognition are thought to be intimately linked, with our knowledge of the correctness of perceptual choices (henceforth metacognition) being dependent on the level of stimulus awareness. Here we used a signal detection theoretic approach involving a Gabor orientation discrimination task in conjunction with trial-by-trial ratings of perceptual awareness and response confidence in order to gauge estimates of type-1 (perceptual) orientation sensitivity and type-2 (metacognitive) sensitivity at different levels of stimulus awareness. Data from three experiments indicate that while the level of stimulus awareness had a profound impact on type-1 perceptual sensitivity, the awareness effect on type-2 metacognitive sensitivity was far lower by comparison. The present data pose a challenge for signal detection theoretic models in which both type-1 (perceptual) and type-2 (metacognitive) processes are assumed to operate on the same input. More broadly, the findings challenge the commonly held view that metacognition is tightly coupled to conscious states.

Determination and correlation of liquid–liquid equilibrium data for the quaternary system 1-octanol+2-methoxy-2-methylbutane+water+methanol at 25°C

Abstract The study of the liquid–liquid equilibria in quaternary systems is not only of interest in order to provide necessary useful data in process design but also to check the thermodynamic models for the treatment of these data. In this work, experimental data of the quaternary system 1-octanol+2-methoxy-2-methyl butane (tert-amyl methyl ether or TAME)+water+methanol at a temperature of 25°C are presented, corresponding to a system with two partially miscible pairs (water+1-octanol and TAME+water). The experimental data have been correlated using three equations, a modified Wilson, NRTL and UNIQUAC models to obtain the binary interaction parameters of these components. These data are also compared to those predicted using the UNIFAC method. The stability of the binary subsystems using a form of the Gibbs free energy in excess is also verified.

Quaternary liquid-liquid equilibria of systems with two partially miscible solvent pairs : 1-octanol + 2-methoxy-2-methylpropane + water + ethanol at 25°C

Abstract Liquid–liquid equilibrium (LLE) data were determined for the quaternary system 1-octanol+2-methoxy-2-methylpropane (MTBE)+water+ethanol at 25°C and atmospheric pressure. The full range of compositions was covered by using pseudoternary systems, each one corresponding to a plane in the tetrahedral phase diagram. The tie-lines for the quaternary mixtures did not always lie within the plane for the corresponding pseudoternary system. The LLE data for the quaternary system, and for its constituent ternary subsystems, were correlated using the NRTL (α=0.1, 0.2 or 0.3), UNIQUAC and TK-Wilson equations. Each correlation afforded similar binary interaction parameters for the partially miscible pairs common to the ternary subsystems. Moreover, these parameters differed little from those obtained for these solvent pairs in the quaternary system. The LLE data were predicted using the UNIFAC method and also using the above-mentioned correlation equations, fixing each binary interaction parameter to the value or mean value obtained by correlating the LLE data for the constituent ternary subsystems.

Effects of spatial attention on detection and identification of oriented lines

In this paper, we study the effects of spatial attention on detection and identification of oriented lines presented at near-threshold luminance. In the first experiment, we found that the cuing effect was greater when observers had to discriminate between two close orientations than when they had to discriminate between two far-apart orientations. In the second experiment, we examined the effects of peripheral cues on summation of low-contrast oriented lines. We found that the range of orientations within which summation occurred was greater when the cues were invalid than when they were valid. Our results suggest that attention to a specific location in the visual field modulates the neural channels which code orientation in at least two different ways: (a) spatial attention increases the responsivity of these channels to stimuli presented at this location, and (b) it reduces the bandwidths or ranges of orientations to which these channels are sensitive. These results suggest that the properties of the orientation-tuned channels, including those that seem to exert their effects at early stages of orientation processing (e.g., tuning function), may not be fixed, but rather vary according to the attention being paid to the spatial region within which the target stimulus is presented.

Table-top laser-based proton acceleration in nanostructured targets

The interaction of ultrashort, high intensity laser pulses with thin foil targets leads to ion acceleration on the target rear surface. To make this ion source useful for applications, it is important to optimize the transfer of energy from the laser into the accelerated ions. One of the most promising ways to achieve this consists in engineering the target front by introducing periodic nanostructures. In this paper, the effect of these structures on ion acceleration is studied analytically and with multi-dimensional particle-in-cell simulations. We assessed the role of the structure shape, size, and the angle of laser incidence for obtaining the efficient energy transfer. Local control of electron trajectories is exploited to maximize the energy delivered into the target. Based on our numerical simulations, we propose a precise range of parameters for fabrication of nanostructured targets, which can increase the energy of the accelerated ions without requiring a higher laser intensity.

Temporal variation in the luminance level of stimuli displayed on a cathode-ray tube monitor: effects on performance on a visual vigilance task

This paper assesses the extent to which the sensitivity decrement frequently observed in vigilance tasks is affected by temporal variations in the luminance level of the stimuli displayed on the screen of a cathode-ray tube (CRT) monitor. First, it was confirmed that the luminance of the stimuli displayed on the screen of the CRT monitor decreases substantially during the first hour after turning the monitor on, and then it remains quite stable. Second, an experiment was carried out in which participants performed a visual vigilance task at three different time periods within which the luminance of the stimuli displayed on the screen of a CRT monitor either decreased or remained stable. The results indicate that the vigilance decrement is modulated by temporal fluctuations of the luminance of the monitor screen, which is used to display the stimuli. However, the relationship between both variables is not simple: the largest sensitivity decrement was not associated with the largest luminance decrement, but to a medium luminance decrement.

Unconscious perception of a flash can trigger line motion illusion.

When a flash of light precedes a static line segment, an illusory motion sensation is observed with the line propagating away from the flash’s location towards the opposite side (Hikosaka et al. in Vision Res 33:1219–1240, 1993). Here we report that a similar illusory motion percept can be triggered by a non-consciously perceived flash. Observers reported illusory line motion (ILM) arising from the flash’s location when a stationary line was presented and the flash was not detected. The results imply that the line motion illusion does not depend on conscious awareness of the flash and suggest that processing of unconscious information can modulate the responses of the neural mechanisms involved in motion perception.