Flexible feature-based inhibition in visual search mediates magnified impairments of selection: evidence from carry-over effects under dynamic preview-search conditions

Evidence for inhibitory processes in visual search comes from studies using preview conditions, where responses to new targets are delayed if they carry a featural attribute belonging to the old distractor items that are currently being ignored-the negative carry-over effect (Braithwaite, Humphreys, & Hodsoll, 2003). We examined whether inhibition was applied in the same manner across different types of displays or whether the inhibitory weighting applied to different features varied with their utility for the search task. To test this, we present the first empirical investigation of negative carry-over effects under the ecologically valid conditions of dynamic visual search. Experiment 1 investigated preview search using dynamic moving and static displays. Detection was very poor when new targets carried the color of the old distractors, and this negative carry-over effect was significantly exaggerated with moving, compared with static, displays. Experiments 2a and 2b demonstrated that this effect could not be attributed to an increased role of preattentive grouping between new and old items for dynamic displays. Collectively, the findings suggest that feature-based inhibition contributes strongly to preview search through dynamic displays, and this leads to an amplified attentional blindness to new targets. The data specifically indicate that inhibitory processes in search differentially weight color and location in moving and static displays, and that feature-based inhibition may underlie many instances of sustained inattentional blindness in everyday life.     

Motivated semantic control: Exploring the effects of extrinsic reward and self-reference on semantic retrieval in semantic aphasia

Recent insights show that increased motivation can benefit executive control, but this effect has not been explored in relation to semantic cognition. Patients with deficits of controlled semantic retrieval in the context of semantic aphasia (SA) after stroke may benefit from this approach since ‘semantic control’ is considered an executive process. Deficits in this domain are partially distinct from the domain-general deficits of cognitive control. We assessed the effect of both extrinsic and intrinsic motivation in healthy controls and SA patients. Experiment 1 manipulated extrinsic reward using high or low levels of points for correct responses during a semantic association task. Experiment 2 manipulated the intrinsic value of items using self-reference, allocating pictures of items to the participant (‘self’) or researcher (‘other’) in a shopping game before participants retrieved their semantic associations. These experiments revealed that patients, but not controls, showed better performance when given an extrinsic reward, consistent with the view that increased external motivation may help ameliorate patients’ semantic control deficits. However, while self-reference was associated with better episodic memory, there was no effect on semantic retrieval. We conclude that semantic control deficits can be reduced when extrinsic rewards are anticipated; this enhanced motivational state is expected to support proactive control, for example, through the maintenance of task representations. It may be possible to harness this modulatory impact of reward to combat the control demands of semantic tasks in SA patients.     

On the relations between implicit and explicit spatial binding: Evidence from Balint’s syndrome

We report two experiments examining whether factors that affect binding in explicit report tasks also affect implicit binding in a patient with Balint’s syndrome, G.K. Replicating prior studies, we showed that there could be implicit binding of visual features in a patient with Balint’s syndrome who was at chance at explicitly discriminating the relations between the features. Nevertheless, when color—form relationships were coded, we showed that G.K.’s implicit binding, as well as his explicit report of binding relationships, was affected by the spatial distance between the stimuli. Similarly, we demonstrated effects of grouping on both implicit and explicit binding of the spatial relations between shapes. We interpret the qualitative similarities between implicit and explicit binding as indicating that they reflect a single process in which binding relations, initially established preattentively, are later consolidated by attention. This later process, of attentional consolidation, is disrupted in Balint’s syndrome.     

Is it impossible to inhibit isoluminant items, or does it simply take longer? Evidence from preview search

Visual search can be facilitated when participants receive a preview of half the distractors (the preview benefit in search; Watson & Humphreys, 1997). Donk and Theeuwes (2001) have argued that preview-based benefits are abolished if the display items are isoluminant to a background. This is consistent with the preview benefit being due to onset capture by the new stimuli. In contrast, the present experiments challenge this suggestion and show that preview benefits can occur under isoluminant conditions, providing that they are given enough time to occur. In Experiment 1, we showed that a preview benefit can occur even with isoluminant stimuli, provided that the old items are previewed for a sufficient time. In Experiment 2, we tested and rejected the idea that this advantage is due to low-level sensory fatigue for the preview stimuli. These findings indicate that the preview effect is not caused solely by onset capture.     

Object-based inhibitory priming in preview search: Evidence from the “top-up” procedure

Visual search in a conjunction task can be facilitated if half the distractor items are previewed prior to the other half of the distractors and the target item. Here, we investigate the nature of this preview by using a top-up procedure, which presents an initial preview followed by a secondary preview after a period of time (the offset period). In Experiment 1, we demonstrate that increasing the time of the offset period decreases search efficiency. If the offset period is increased to 2 sec, the previewed items are searched to a greater extent than when the offset period is 450 msec. This holds even when the old items remain in the same positions across presentations and when they differ in color from new search stimuli. However, when the offset intervals are reduced, the preview can be discounted from search even when the old items change locations between exposures (Experiment 2) and when they are not distinguished from search displays by their color (Experiment 3). The last result occurs only as long as the preview items can be grouped in terms of form. When the preview stimuli are heterogeneous, they are no longer discounted from search if their locations change across the offset period (Experiment 4). We interpret the data in terms of object-based priming, which enables the repeated form of the old distractors to be filtered more easily from search.     

Sustained vs. transient cognitive control: Evidence of a behavioral dissociation

This study assessed whether two well known effects associated with cognitive control, conflict adaptation (the Gratton effect) and conflict context (proportion congruent effects), reflect a single common or separate control systems. To test this we examined if these two effects generalized from one kind of conflict to another by using a combined-conflict paradigm (involving the Simon and Spatial Stroop tasks) and manipulating the proportion of congruent to incongruent trials for one conflict (Simon) but not the other (Spatial Stroop). We found that conflict adaptation effects did not generalize, but the effect of conflict context did. This contrasting pattern of results strongly suggests the existence of two separate attentional control systems, one transient and responsible of online regulation of performance (conflict adaptation), the other sustained and responsible for conflict context effects.     

An interactive activation approach to object processing: Effects of structural similarity,name frequency,and task in normality and pathology

Abstract

We present a computational model of the processes involved in retrieving stored semantic and name information from objects, using a simple interactive activation and competition architecture. We simulate evidence showing a cross-over in normal reaction times to make semantic classification and identification responses to objects from categories with either structurally similar or structurally dissimilar exemplars, and that identification times to objects from these two different classes correlate differentially with measures of the structural similarity of objects within the category and the frequency of the object's name. Structural similarity exerts a negative effect on object decision as well as naming, though this effect is larger on naming. Also, on naming, structural similarity interacts with the effects of name frequency, captured in the model by varying the weight on connections from semantic to name units; frequency effects are larger with structurally dissimilar items. In addition, (1) the range of potential errors for objects from these two classes, when responses are elicited before activation reached a stable state, differ–a wider range of errors occur to objects from categories with structurally similar exemplars; and (2) simulated lesions to different locations within the model produce selective impairments to identification but not to semantic classification responses to objects from categories with structurally similar exemplars. We discuss the results in relation to data on visual object processing in both normality and pathology.     

The stalking of psychotherapists by current or former clients: Beware of the insecurely attached!

Abstract

A survey of psychological therapists who worked in primary care showed that the incidence of psychotherapists being harassed or stalked by their current or former clients was more than twice the national average at 24%. The stalkers fell into three broad categories: those clients who were needy and made early attachments to their therapists; those experiencing erotic transference; and those with personality disorders, especially those with a narcissistic style. All of these are disorders of attachment. This paper discusses the neurobiological development of an insecure attachment and how that manifests during therapy in stalking behaviour. Psychotherapists who are aware of the dynamics within the therapeutic relationship can take preventative steps to inhibit the automatic fear response of a client who is insecurely attached and which may lead to stalking behaviour.

A survey of psychological therapists who worked in primary care showed that the incidence of psychotherapists being harassed or stalked by their current or former clients was more than twice the national average at 24%. The stalkers fell into three broad categories: those clients who were needy and made early attachments to their therapists; those experiencing erotic transference; and those with personality disorders, especially those with a narcissistic style. All of these are disorders of attachment. This paper discusses the neurobiological development of an insecure attachment and how that manifests during therapy in stalking behaviour. Psychotherapists who are aware of the dynamics within the therapeutic relationship can take preventative steps to inhibit the automatic fear response of a client who is insecurely attached and which may lead to stalking behaviour.     

A biased-competition approach to spatial cueing: Combining empirical studies and computational modelling

We examined the effects of cue luminance on visual orienting. Experiment 1 established that the commonly-found early facilitation and late inhibition of return (IOR) effects were independent of cue luminance with single cues in terms of their amplitude, although IOR was delayed in the low compared to the high luminance cue condition. In contrast, Experiment 2 revealed that, with dual cues of mixed luminance, both facilitation and IOR effects were found only with bright cues. When cues had equal luminance, however, there were cueing effects for two cued locations but only when the cues were bright. The data were accommodated in a neural network model of biased competition in which cueing effects emerge at more than one location provided input activation is sufficient to overcome competitive damping of the selection system.