History matters: the preview benefit in search is not onset capture

Visual search for a conjunction target is made easier when distractor items are temporally segregated over time to produce two separate old and new groups (the new group containing the target item). The benefit of presenting half the distractors first is known as the preview effect. Recently, some researchers have argued that the preview effect occurs because new stimuli capture attention. This account was tested in the present study by using a novel "top-up" condition that exploits the fact that when previews appear only briefly before the search display, there is minimal preview benefit. We show that effects of a brief preview can be "topped up" by an earlier exposure of the same items, even when the preview disappears between its first and second presentations.This top-up effect demonstrates that the history of the old stimuli is important for the preview benefit, contrary to the account favoring onset capture. We discuss alternative accounts of how the preview benefit arises.     

An analysis of the time course of attention in preview search

We used a probe dot procedure to examine the time course of attention in preview search (Watson & Humphreys, 1997). Participants searched for an outline red vertical bar among other new red horizontal bars and old green vertical bars, superimposed on a blue background grid. Following the reaction time response for search, the participants had to decide whether a probe dot had briefly been presented. Previews appeared for 1,000 msec and were immediately followed by search displays. In Experiment 1, we demonstrated a standard preview benefit relative to a conjunction search baseline. In Experiment 2, search was combined with the probe task. Probes were more difficult to detect when they were presented 1,200 msec, relative to 800 msec, after the preview, but at both intervals detection of probes at the locations of old distractors was harder than detection on new distractors or at neutral locations. Experiment 3A demonstrated that there was no difference in the detection of probes at old, neutral, and new locations when probe detection was the primary task and there was also no difference when all of the shapes appeared simultaneously in conjunction search (Experiment 3B). In a final experiment (Experiment 4), we demonstrated that detection on old items was facilitated (relative to neutral locations and probes at the locations of new distractors) when the probes appeared 200 msec after previews, whereas there was worse detection on old items when the probes followed 800 msec after previews. We discuss the results in terms of visual marking and attention capture processes in visual search.     

A context noise model of episodic word recognition

Item noise models of recognition assert that interference at retrieval is generated by the words from the study list. Context noise models of recognition assert that interference at retrieval is generated by the contexts in which the test word has appeared. The authors introduce the bind cue decide model of episodic memory, a Bayesian context noise model, and demonstrate how it can account for data from the item noise and dual-processing approaches to recognition memory. From the item noise perspective, list strength and list length effects, the mirror effect for word frequency and concreteness, and the effects of the similarity of other words in a list are considered. From the dual-processing perspective, process dissociation data on the effects of length, temporal separation of lists, strength, and diagnosticity of context are examined. The authors conclude that the context noise approach to recognition is a viable alternative to existing approaches.     

Spatially parallel processing of within-dimension conjunctions

Within-dimension conjunction search for red-green targets amongst red-blue, and blue-green, nontargets is extremely inefficient (Wolfe et al, 1990 Journal of Experimental Psychology: Human Perception and Performance 16 879-892). We tested whether pairs of red-green conjunction targets can nevertheless be processed spatially in parallel. Participants made speeded detection responses whenever a red-green target was present. Across trials where a second identical target was present, the distribution of detection times was compatible with the assumption that targets were processed in parallel (Miller, 1982 Cognitive Psychology 14 247-279). We show that this was not an artifact of response-competition or feature-based processing. We suggest that within-dimension conjunctions can be processed spatially in parallel. Visual search for such items may be inefficient owing to within-dimension grouping between items.     

Distributed and focused attention: neuropsychological evidence for separate attentional mechanisms when counting and estimating

Evidence is presented for 2 modes of attention operating in simultanagnosia. The authors examined visual enumeration in a patient, GK, who has severe impairments in serially scanning across a scene and is unable to count the numbers of items in visual displays. However, GK's ability to judge the relative magnitude of 2 displays was consistently above chance, even when overall luminosity did not vary with the number of items present. In addition, several variables had a differential impact on GK's counting and magnitude estimation. Magnitude estimation but not counting was facilitated by using elements that grouped more easily and by presenting the elements in regular configurations. In contrast, counting was facilitated by placing the elements in different colors while magnitude estimation was disrupted. Also GK's performance on magnitude estimation tasks was disrupted by asking him to count the elements present. The data suggest that GK can process visual stimuli in either a focused or distributed attention mode. When in a focused attention mode, performance is limited by poor serial scanning of attention due to an impaired explicit representation of visual space.     

Inhibitory tagging in inhibition of return: Evidence from flanker interference with multiple distractor features

Fuentes, Vivas, and Humphreys (1999) proposed a distinction betweeninhibition of return (IOR) and inhibitory processing taking place at a location subject to IOR. This latter mechanism,inhibitory tagging (IT), would act at a late level of processing related to response selection. In the present study, we examined whether IT was applied only to the target-relevant properties of the stimuli (e.g., to its color) or whether it was applied to other features of the stimulus as well (e.g., to its shape). Both when the task was to respond to the target’s color (Experiment 1) as well as when it was to respond to the target’s shape (Experiment 2), there was evidence of IT (reversal of the typical flanker effect at the cued location, relative to the uncued location) only to task-relevant features of the target. These findings suggest that IT is a central process of control constrained by task demands and current goals.     

Researching self-help/mutual aid groups and organizations: Many roads, one journey

Self-help and mutual help groups are defined and the status of the literature described and reviewed. Self-help groups are different from peer and nonprofessional services under the supervision of professionals. Controlled studies of mutual help groups may be neither possible nor desirable as the method of choice by which to understand the phenomena of interest. Other approaches to research, including worldly evaluations, and ways of construing self-help organizations, that is, as normative communities and political action organizations rather than as psychological treatments, are discussed, and suggestions for future research are presented.     

Information‐Seeking as a Precaution Behavior: Exploring the Role of Decision‐Making Stages

The Planned Risk Information Seeking Model (PRISM) was employed to explain people's information‐seeking intentions in the context of hydraulic fracturing. Stages from the Precaution Adoption Process Model (PAPM) were included in the analysis as a moderator. The PRISM fit the data well. Moreover, results showed overall model differences among people who have not decided to take action on hydraulic fracturing, people who have decided to take action, and people who have decided not to take action. Findings provided justifications for tailored messages to encourage information seeking among the varying publics.     

Parieto-occipital areas involved in efficient filtering in search: A time course analysis of visual marking using behavioural and functional imaging procedures

Search for a colour-form conjunction target can be facilitated by presenting one set of distractors prior to the second set of distractors and the target: the preview benefit (Watson & Humphreys, 1997). The early presentation of one set of distractors enables them to be efficiently filtered from search. We report two studies investigating the time course of the preview benefit. In Experiment 1 we use a standard reaction time analysis to show that the benefit has a relatively slow time course; old items need to precede the new set by 600 ms or more in order to be fully filtered from search. Furthermore, the reductions in reaction time across time in the preview condition varied nonlinearly with the display size, suggesting that old items were discounted from search in parallel. In Experiment 2 we examined the neural locus of this filtering effect over time, using positron emission tomography (PET). We show that regions of parieto-occipital cortex are selectively activated in a preview search condition relative to a detection baseline. These regions also increase in activation as the preview interval increases (and search then becomes easier), consistent with them modulating the parallel filtering of distractors from targets in spatial search. Interestingly, the same areas as those activated in preview search were also active in conjunction search relative to its own detection baseline. Thus these regions either modulate parallel filtering in conjunction search too, or they modulate different behavioural functions according to task constraints.     

Working memory, perceptual priming, and the perception of hierarchical forms: Opposite effects of priming and working memory without memory refreshing

Previous research has shown that stimuli held in working memory (WM) can influence spatial attention. Using Navon stimuli, we explored whether and how items in WM affect the perception of visual targets at local and global levels in compound letters. Participants looked for a target letter presented at a local or global level while holding a regular block letter as a memory item. An effect of holding the target’s identity in WM was found. When memory items and targets were the same, performance was better than in a neutral condition when the memory item did not appear in the hierarchical letter (a benefit from valid cuing). When the memory item matched the distractor in the hierarchical stimulus, performance was worse than in the neutral baseline (a cost on invalid trials). These effects were greatest when the WM cue matched the global level of the hierarchical stimulus, suggesting that WM biases attention to the global level of form. Interestingly, in a no-memory priming condition, target perception was faster in the invalid condition than in the neutral baseline, reversing the effect in the WM condition. A further control experiment ruled out the effects of WM being due to participants’ refreshing their memory from the hierarchical stimulus display. The data show that information in WM biases the selection of hierarchical forms, whereas priming does not. Priming alters the perceptual processing of repeated stimuli without biasing attention.