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.     

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.     

Effects of action relations on the configural coding between objects

Configural coding is known to take place between the parts of individual objects but has never been shown between separate objects. We provide novel evidence here for configural coding between separate objects through a study of the effects of action relations between objects on extinction. Patients showing visual extinction were presented with pairs of objects that were or were not co-located for action. We first confirmed the reduced extinction effect for objects co-located for action. Consistent with prior results showing that inversion disrupts configural coding, we found that inversion disrupted the benefit for action-related object pairs. This occurred both for objects with a standard canonical orientation (e.g., teapot and teacup) and those without, but where grasping and using the objects was made more difficult by inversion (e.g., spanner and nut). The data suggest that part of the affordance effect may reflect a visuo-motor response to the configural relations between stimuli. Experiment 2 showed that distorting the relative sizes of the objects also reduced the advantage for action-related pairs. We conclude that action-related pairs are processed as configurations.     

Temporal contexts: filling the gap between episodic memory and associative learning

People can create temporal contexts, or episodes, and stimuli that belong to the same context can later be used to retrieve the memory of other events that occurred at the same time. This can occur in the absence of direct contingency and contiguity between the events, which poses a challenge to associative theories of learning and memory. Because this is a learning and memory problem, we propose an integrated approach. Theories of temporal contexts developed in the memory tradition provide interesting predictions that we test using the methods of associative learning to assess their generality and applicability to different settings and dependent variables. In 4 experiments, the integration of these 2 areas allows us to show that (a) participants spontaneously create temporal contexts in the absence of explicit instructions; (b) cues can be used to retrieve an old temporal context and the information associated with other cues that were trained in that context; and (c) the memory of a retrieved temporal context can be updated with information from the current situation that does not fit well with the retrieved memory, thereby helping participants to best adapt their behavior to the future changes of the environment.