Among non-smokers and non-daily cigarette smokers, plain packaging appears to increase visual attention towards health warning information and away from brand information.

These data are the first to show alterations in attentional bias for smoking-related stimuli following a modified visual probe training procedure. Furthermore, post-training group differences in subjective craving suggest potential clinical utility of training procedures, although these effects may operate only in males. Future research should investigate whether multiple training sessions enhance post-training reductions in craving and cue reactivity, and the longer-term persistence of training effects.

Scene segmentation and perceptual grouping are important operations in visual processing. Pattern elements constituting individual perceptual objects need to be segregated from those of other objects and the background and have to be bound together for further joint evaluation. Both textural (spatial) and temporal cues are exploited for this grouping operation. Thus, pattern elements might get bound that share certain textural features and/or appear in close spatial or temporal contiguity. However, results on the involvement of temporal cues in perceptual grouping are contradictory [Kiper et al. (1991). Society for Neuroscience Abstracts, 17, 1209; Fahle (1993). Proceedings of the Royal Society of London B, 254, 199-203]. We therefore reinvestigated the relative contributions of temporal and spatial cues and their interactions in a texture-segmentation paradigm. Our data show that the visual system can segregate figures solely on the basis of temporal cues if the temporal offset between figure and ground elements exceeds 10 msec. Moreover, segregation of figures defined by orientation differences among pattern elements is facilitated by additional temporal cues if these define the same figure. If temporal and textural cues define different figures, the two cues compete and only the more salient pattern is perceived. By contrast, the detection of a figure defined by orientation is not impaired by conflicting temporal cues if these do not define a figure themselves and do not exceed offset intervals of 100 msec. These results indicate the existence of a flexible binding mechanism that exploits both temporal and textural cues either alone or in combination if they serve perceptual grouping but can exclude either of the two cues if they are in conflict or do not define a figure. It is proposed that this flexibility is achieved by the implementation of two segmentation mechanisms which differ in their sensitivity for spatial and temporal cues and interact in a facultative way.

The human visual system is usually confronted with many different objects at a time, with only some of them reaching consciousness. Reaction-time studies have revealed two different strategies by which objects are selected for further processing: an automatic, efficient search process, and a conscious, so-called inefficient search [Treisman, A. (1991). Search, similarity, and integration of features between and within dimensions. Journal of Experimental Psychology: Human Perception and Performance, 17, 652--676; Treisman, A., & Gelade, G. (1980). A feature integration theory of attention. Cognitive Psychology, 12, 97--136; Wolfe, J. M. (1996). Visual search. In H. Pashler (Ed.), Attention. London: University College London Press]. Two different theories have been proposed to account for these search processes. Parallel theories presume that both types of search are treated by a single mechanism that is modulated by attentional and computational demands. Serial theories, in contrast, propose that parallel processing may underlie efficient search, but inefficient searching requires an additional serial mechanism, an attentional "spotlight" (Treisman, A., 1991) that successively shifts attention to different locations in the visual field. Using functional magnetic resonance imaging (fMRI), we show that the cerebral networks involved in efficient and inefficient search overlap almost completely. Only the superior frontal region, known to be involved in working memory [Courtney, S. M., Petit, L., Maisog, J. M., Ungerleider, L. G., & Haxby, J. V. (1998). An area specialized for spatial working memory in human frontal cortex. Science, 279, 1347--1351], and distinct from the frontal eye fields, that control spatial shifts of attention, was specifically involved in inefficient search. Activity modulations correlated with subjects' behavior best in the extrastriate cortical areas, where the amount of activity depended on the number of distracting elements in the display. Such a correlation was not observed in the parietal and frontal regions, usually assumed as being involved in spatial attention processing. These results can be interpreted in two ways: the most likely is that visual search does not require serial processing, otherwise we must assume the existence of a serial searchlight that operates in the extrastriate cortex but differs from the visuospatial shifts of attention involving the parietal and frontal regions.

Among experimenters and weekly smokers, plain packaging increases visual attention to health warnings and away from branding. Daily smokers, even relatively early in their smoking careers, seem to avoid the health warnings on cigarette packs. Adolescent never-smokers attend the health warnings preferentially on both types of packs, a finding which may reflect their decision not to smoke.

Smokers actively avoid cigarette pack health warnings, and this remains the case even in the absence of salient branding information. Smokers may have learned to divert their attention away from cigarette pack health warnings. These findings have implications for cigarette packaging and health warning policy.

Illumination varies greatly both across parts of a natural scene and as a function of time, whereas the spectral reflectance function of surfaces remains more stable and is of much greater relevance when searching for specific targets. This study investigates the functional properties of postreceptoral opponent-channel responses, in particular regarding their stability against spatial and temporal variation in illumination. We studied images of natural scenes obtained in UK and Uganda with digital cameras calibrated to produce estimated L-, M-, and S-cone responses of trichromatic primates (human) and birds (starling). For both primates and birds we calculated luminance and red-green opponent (RG) responses. We also calculated a primate blue-yellow-opponent (BY) response. The BY response varies with changes in illumination, both across time and across the image, rendering this factor less invariant. The RG response is much more stable than the BY response across such changes in illumination for primates, less so for birds. These differences between species are due to the greater separation of bird L and M cones in wavelength and the narrower bandwidth of the cone action spectra. This greater separation also produces a larger chromatic signal for a given change in spectral reflectance. Thus bird vision seems to suffer a greater degree of spatiotemporal "clutter" than primate vision, but also enhances differences between targets and background. Therefore, there may be a trade-off between the degree of chromatic clutter in a visual system versus the degree of chromatic difference between a target and its background. Primate and bird visual systems have found different solutions to this trade-off.

Simulations of artificial vision were performed to assess "minimum requirements for useful artificial vision". Retinal prostheses will be implanted at a fixed (and probably eccentric) location of the retina. To mimic this condition on normal observers, we projected stimuli of various sizes and content on a defined stabilised area of the visual field. In experiment 1, we asked subjects to read isolated 4-letter words presented at various degrees of pixelisation and at various eccentricities. Reading performance dropped abruptly when the number of pixels was reduced below a certain threshold. For central reading, a viewing area containing about 300 pixels was necessary for close to perfect reading (>90% correctly read words). At eccentricities beyond 10 degrees, close to perfect reading was never achieved even if more than 300 pixels were used. A control experiment using isolated letter recognition in the same conditions suggested that lower reading performance at high eccentricity was in part due to the "crowding effect". In experiment 2, we investigated whether the task of eccentric reading under such specific conditions could be improved by training. Two subjects, naive to this task, were trained to read pixelised 4-letter words presented at 15 degrees eccentricity. Reading performance of both subjects increased impressively throughout the experiment. Low initial reading scores (range 6%-23% correct) improved impressively (range 64%-85% correct) after about one month of training (about 1 h/day). Control tests demonstrated that the learning process consisted essentially in an adaptation to use an eccentric area of the retina for reading. These results indicate that functional retinal implants consisting of more than 300 stimulation contacts will be needed. They might successfully restore some reading abilities in blind patients, even if they have to be placed outside the foveal area. Reaching optimal performance may, however, require a significant adaptation process.