Predators are known to select food of the same type in non-random sequences or “runs” that are longer than would be expected by chance. If prey are conspicuous, predators will switch between available sources, interleaving runs of different prey types. However, when prey are cryptic, predators tend to focus on one food type at a time, effectively ignoring equally available sources. This latter finding is regarded as a key indicator that animal foraging is strongly constrained by attention. It is unknown whether human foraging is equally constrained. Here, using a novel iPad task, we demonstrate for the first time that it is. Participants were required to locate and touch 40 targets from 2 different categories embedded within a dense field of distractors. When individual target items “popped-out” search was organized into multiple runs, with frequent switching between target categories. In contrast, as soon as focused attention was required to identify individual targets, participants typically exhausted one entire category before beginning to search for the other. This commonality in animal and human foraging is compelling given the additional cognitive tools available to humans, and suggests that attention constrains search behavior in a similar way across a broad range of species.

Imagine yourself at a party with someone that you have a crush on or are even in love with. You seem to be constantly aware of where that person is, and your gaze is repeatedly drawn toward the dashing red shirt or dress that he or she is wearing or to their shining black hair, in such fine contrast to their paler face, despite your best efforts to not look too eager. This person is an example of a stimulus that is the focus of your attention and matters very much to you. Recent research has unveiled how our attention and gaze seem to be automatically drawn toward those features that we have recently attended to and are important to us, such as the red dress or dark hair of our object of desire. Such priming appears to have a very strong effect on what grabs our attention. Recent research on priming in visual search tasks suggests that we possess a primitive memory system drawing our attention to features or objects that we have recently attended to and are important to our goals or to the task that we are performing. We seem to have little or no voluntary control over the workings of this memory system. We review a large body of neurophysiological and neuropsychological evidence with regard to such priming that suggests that activity changes in the neural mechanisms devoted to the analysis of the particular stimuli for which priming effects are seen are the source of the observed priming effects and that these activity modulations occur at a number of different levels of the visual hierarchy. Basic Characteristics of PrimingSince the pioneering studies of Maljkovic and Nakayama (1994, 1996) and Treisman (1992), a large number of studies have addressed priming effects in visual search. This research has shown that our perception is heavily influenced by what we have seen in the past. As we search for a target of, say, a particular color, detection or discrimination of that target or features of that target (such as its shape, color, or location) becomes easier if we are familiar with it or if we have seen it or acted upon it before. This has been widely investigated by means of controlled lab experiments in which the effects of previously presented displays on performance in the present have been investigated. Such effects, called perceptual What we have recently seen and attended to strongly influences how we subsequently allocate visual attention. A clear example is how repeated presentation of an object's features or location in visual search tasks facilitates subsequent detection or identification of that item, a phenomenon known as priming. Here, we review a large body of results from priming studies that suggest that a short-term implicit memory system guides our attention to recently viewed items. The nature of this memory system and the processing level at which visual priming occurs are still debated. Priming might be due to activity modulations of low-level areas coding simple stimulus characteristics or to higher level episodic memory representations of whole objects or visual scenes. Indeed, recent ...

To assess the role of priming in conjunctive visual search tasks, we systematically varied the consistency of the target and distractor identity between different conditions. Search was fastest in the standard conjunctive search paradigm where identities remained constant. Search was slowest when potential target identity varied predictably for each successive trial (the 'switch' condition). The role of priming was also demonstrated on a trial-by-trial basis in a 'streak' condition where target and distractor identity was unpredictable yet was consistent within streaks. When the target to be found was the same for a few trials in a row, search performance became similar to that when the potential target was the same on all trials. A similar pattern was found for the target absent trials, suggesting that priming is based on the whole search array rather than just the target in each case. Further analysis indicated that the effects of priming are sufficiently strong to account for the advantage seen for the conjunctive search task. We conclude that the role of priming in visual search is underestimated in current theories of visual search and that differences in search times often attributed to top-down guidance may instead reflect the benefits of priming. q

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Detailed measurements of saccadic latency--the time taken to make an eye movement to a suddenly-presented visual target--have proved a valuable source of detailed and quantitative information in a wide range of neurological conditions, as well as shedding light on the mechanisms of decision, currently of intense interest to cognitive neuroscientists. However, there is no doubt that more complex oculomotor tasks, and in particular the antisaccade task in which a participant must make a saccade in the opposite direction to the target, are potentially more sensitive indicators of neurological dysfunction, particularly in neurodegenerative conditions. But two obstacles currently hinder their widespread adoption for this purpose. First, that much of the potential information from antisaccade experiments, notably about latency distribution and amplitude, is typically thrown away. Second, that there is no standardised protocol for carrying out antisaccade experiments, so that results from one laboratory cannot easily be compared with those from another. This paper, the outcome of a recent international meeting of oculomotor scientists and clinicians with an unusually wide experience of such measurements, sets out a proposed protocol for clinical antisaccade trials: its adoption will greatly enhance the clinical and scientific benefits of making these kinds of measurements.