A new look at novelty effects: Guiding search away from old distractors

We examined whether search is guided to novel distractors. In Experiment 1, subjects searched for a target among one new and a variable number of old distractors. Search displays in Experiment 2 consisted of an equal number of new, old, and familiar distractors (the latter repeated occasionally). We found that eye movements were preferentially directed to a new distractor on target-absent trials and that subjects tended to immediately fixate a new distractor after leaving the target on target-present trials. In both cases, first fixations on old distractors were consistently less frequent than could be explained by chance. We interpret these patterns as evidence for negative guidance: Subjects learn the visual features associated with the set of old distractors and then guide their search away from these features, ultimately resulting in the preferential fixation of novel distractors.     

Eye movements in search in visual neglect

We report data on eye movements in a patient (MP) with unilateral visual neglect, in a task of searching a real-world scene. We demonstrate that MP missed some contralesional targets after fixating on them. On such “miss”; trials, MP's eye movements were similar to those on objects in target-absent trials trials, where MP was cued to search for a target that was not actually present. In addition, MP showed little evidence of memory for the locations of objects that remained across a trial, though poor memory fails to explain performance on trials where targets were fixated. We suggest that, in this case, neglect reflected the poor uptake of information from the contralesional side of space, so that even fixated targets sometimes failed to match a “template” held in his memory.     

The associated nontargets effect: Evidence of nontarget processing at and beyond the level of letter recognition

In four visual search tasks participants were asked to make a target response if either of two targets was present and to make a nontarget response if neither target was present. Some target-absent displays included only nontarget stimuli or features that never occurred in the same displays as targets, whereas other target-absent displays included nontarget stimuli or features that did sometimes occur with targets. Nontarget responses were reliably faster in the former case than in the latter. This “associated nontargets effect” indicates that nontargets are not simply classified as nontargets but in addition are discriminated from one another. Current visual search models may underestimate the degree to which nontargets are processed during search.     

Obsessive compulsive disorder,checking, and non-verbal memory: a neuropsychological investigation

There is considerable evidence in the literature for the presence of non-verbal and praxic memory deficits in OCD. Such deficits may represent the cognitive substrate of doubt-related phenomenon such as checking. Neuropsychological tests of non-verbal memory functioning and memory for actions were administered to patients with OCD (whose predominant symptom was checking) and a group of matched healthy controls. Significant differences were found between the experimental and control groups, suggesting some memory impairment in the OCD group; however, no significant relationship was found linking neuropsychological test indices with checking. Significant relationships were found linking recognition memory problems and immediate memory for actions with general symptom severity.     

Mechanisms of the associated nontargets effect: Processes influenced by statistical learning in a simple visual environment

In three visual search experiments participants were asked to make a target response if either of two targets was present and to make a nontarget response if neither target was present. Some target-absent displays included only nontarget features that never occurred in the same displays as target features, whereas other target-absent displays included nontarget features that did sometimes occur with target features. Nontarget responses were reliably faster in the former case than in the latter. This “associated nontargets effect” appears to arise from participants' ability to learn and to use contingencies between the presence of certain nontargets and the absence of any target.     

Words may not be enough! No increased emotional Stroop effect in obsessive-compulsive disorder

Conflicting evidence has been obtained whether or not patients diagnosed with obsessive-compulsive disorder (OCD) share an attentional bias towards disorder-related stimuli. Some of these inconsistencies can be accounted for by suboptimal stimuli selection. In consideration of the heterogeneity of OCD, we investigated Stroop interference effects for two classes of OCD items (i.e., washing and checking) in 23 OCD patients and 23 healthy controls. In order to cover prevalent OCD concerns, item compilation was based on experts' appraisals. Patients neither displayed greater immediate as well as delayed Stroop interference nor any bias for OCD and subtype-congruent stimuli. On the contrary, for washing-related items, OCD patients, and here especially washers, displayed facilitation relative to healthy controls. Although the present study at first sight refutes the notion of an attentional bias in OCD in contrast to other anxiety disorders, several potential moderators need to be considered before this account is ultimately dismissed. In particular, an attentional bias may only be elicited using visual material that is more attention-grabbing than verbal stimuli. Finally, blockwise instead of random item administration and greater consideration of individual relevance may be crucial prerequisites for the effect to emerge.     

Distracted by relatives: Effects of frontal lobe damage on semantic distraction

When young adults carry out visual search, distractors that are semantically related, rather than unrelated, to targets can disrupt target selection (see 2 and 22). This effect is apparent on the first eye movements in search, suggesting that attention is sometimes captured by related distractors. Here we assessed effects of semantically related distractors on search in patients with frontal-lobe lesions and compared them to the effects in age-matched controls. Compared with the controls, the patients were less likely to make a first saccade to the target and they were more likely to saccade to distractors (whether related or unrelated to the target). This suggests a deficit in a first stage of selecting a potential target for attention. In addition, the patients made more errors by responding to semantically related distractors on target-absent trials. This indicates a problem at a second stage of target verification, after items have been attended. The data suggest that frontal lobe damage disrupts both the ability to use peripheral information to guide attention, and the ability to keep separate the target of search from the related items, on occasions when related items achieve selection.     

Phenomenological validity of an OCD-memory model and the remember/know distinction

In earlier experiments using interactive computer animation with healthy subjects, it was found that displaying compulsive-like repeated checking behavior affects memory. That is, checking does not alter actual memory accuracy, but it does affect 'meta-memory': as checking continues, recollections are experienced as less vivid and less detailed while confidence in memory is undermined. This procedure provides a model of OCD checking and suggests that checking is a counterproductive strategy to reduce memory distrust. The present experiment was carried out to specify the phenomenological quality of memory distrust after checking and to see if repeated checking produces a shift in the memory source that is used to decide about the outcome of checking: from 'remembering' to 'knowing' (Tulving, 1985). Using the same interactive computer-animation, the earlier findings on vividness, detail and confidence were replicated. In addition, it was found that checking made participants endorse quotations from OCD patients (Reed, 1985) expressing a specific ambivalence about memory: 'It is as though the memory is there, but is isn't definite enough', 'I remember doing it in a way, but it's all fuzzy....' And 'I can remember that I've done it. But the memory isn't clear somehow'. This finding adds to the validity of the experimental model. Furthermore, after checking subjects' beliefs about the outcome of checking became based on (general) knowing instead of (specific) remembering. It is suggested that OCD checkers feel a general and relatively strong need to be certain about the veracity of recollections and that they have high standards for memory performance. This may explain earlier findings that OCD checkers have a general tendency to distrust their episodic memory. A need for certainty and a critical attitude towards memory performance may not be problematic or abnormal. It is suggested that clinical problems arise when the patient tries to fight memory distrust by repeated checking. The latter does not reduce distrust but rather increases distrust and the patient may get trapped in a spiral of mutually reinforcing checking behavior and memory distrust.     

Enhanced perceived responsibility decreases metamemory but not memory accuracy in obsessive-compulsive disorder (OCD)

Mixed findings have been obtained in prior research with respect to the presence and severity of memory and metamemory deficits in obsessive-compulsive disorder (OCD). We tested the hypothesis that experimentally induced increments of subjective responsibility would lead to a disproportionately strong decline of memory confidence and enhanced response latencies in OCD while leaving memory accuracy unaffected. Twenty-eight OCD patients and 28 healthy controls were presented a computerized memory test framed with two different scenarios. In the neutral scenario, the participant was requested to imagine purchasing 15 items from a do-it-yourself store. In the recognition phase, the 15 needed items were presented along with 15 distractor items. The participant was asked to decide whether items were on his or her shopping list or not, graded by subjective confidence. In the responsibility scenario, the general experimental setup was analogous except that the participant now had to envision that he or she was a helper in a region recently struck by an earthquake, dispatched to provide 15 urgently needed goods from a nearby town. In line with prior work by our group, samples did not differ in either condition on memory accuracy in a subsequent recognition task. As hypothesized, OCD participants were less certain in their responses for the high responsibility condition than controls. Whereas patients and controls did not differ in their subjective estimates for memorized items, patients expressed stronger doubt that their earthquake mission was successful. The findings indicate that low memory confidence in OCD may only be elicited in situations where perceived responsibility is high and that patients may share higher performance standards ("good is not good enough") than controls when perceived responsibility is inflated.     

Is thought-action fusion specific to obsessive-compulsive disorder?: a mediating role of negative affect

Thought-action fusion (TAF) is a cognitive bias presumed to underlie the development of obsessional problems (i.e. obsessive-compulsive disorder; OCD). Previous studies have found that TAF is related to not only OCD, but also to other anxiety disorders. In the present study we compared levels of TAF in OCD patients and in patients with other anxiety disorders, depression, and healthy controls to examine whether TAF is characteristic of individuals with emotional distress in general, as opposed to anxiety disorders per se. We also examined whether negative affect (i.e. anxiety and depression) mediates the relationship between OCD and TAF. Results indicated that OCD patients were characterized by higher scores on likelihood-self and likelihood-other TAF, but that this difference was predominately due to differences in negative affect. These findings support a model in which negative affect mediates the relationship between OCD and TAF.     

Relationships between anger, symptoms, and cognitive factors in OCD checkers

The purpose of this study was to examine whether individuals diagnosed with obsessive-compulsive disorder (OCD) with primary checking compulsions report higher levels of trait anger and anger expression compared with a student control group, and whether trait anger and anger expression are correlated with specific beliefs and interpretations that are common among individuals who compulsively check. A group of individuals with OCD reporting significant checking compulsions (n=33) and a group of undergraduate students (n=143) completed a questionnaire package that included measures of trait anger and anger expression, as well as measures of obsessive-compulsive symptoms and beliefs. The compulsive checking group reported greater trait anger, though not greater anger expression, than the student control group. Furthermore, beliefs concerning perfectionism and intolerance of uncertainty were positively correlated with anger expression and trait anger among compulsive checkers but not among the student control group. The implications of these findings are discussed in terms of cognitive-behavioural treatments for and models of compulsive checking in OCD.     

Responsibility and obsessive-compulsive disorder: an experimental test

To test the causal status of responsibility in obsessive-compulsive disorder (OCD), an experiment was executed in which responsibility was experimentally manipulated. OCD patients, non-OCD anxiety controls, and non-patients executed a classification task in either a high or a low responsibility (LoRes) condition. Subjective ratings related to danger and responsibility indicated that the manipulation was successful. Subjective OCD-like experiences and checking behaviors were higher in OCD patients in the high responsibility (HiRes) condition than in all other groups. Although the checking subscale of the Padua Inventory correlated with subjective ratings in the OCD patients in the HiRes condition, it was not associated with checking behaviors. The results confirm the hypothesis that responsibility plays a causal role in OCD.     

Age differences in the distractor-ratio effect as a function of contrast level

Latencies (RT) and eye movement measures were used to examine the effects of age and contrast on the distractor-ratio effect (DRE) in visual search. Younger and older adults performed a contrast x orientation conjunction search task where the ratios of white to black distractors and luminance contrast levels were varied. The distractor-ratio manipulation had similar effects for older and younger adults on both RT and the number of fixations required to find the target. Both measures were largely independent of distractor ratio on target-present trials, while both RTs and the fixation number increased with the number of items sharing the target's contrast polarity on target-absent trials. A more detailed analysis of eye movements suggested that younger adults were a bit more adept at attending to the smaller set of distractors, which presumably facilitated both overt and covert search. Generalized slowing can account for the age differences in RT, but the fixation number data speak to another mechanism, perhaps increased cautiousness on the part of the elderly when signal strength is low.     

Effect of forget instructions with and without the conditions for selective search*

A PA probe experiment was conducted to determine whether a mechanism other than selective search is involved in the Only effect of directed forgetting. To accomplish this, a small number of trials which tested all pairs in the list successively (“all” trials) were intermixed with the standard single-probe trials. On “single” trials, both pretest mechanisms and selective search may operate, but on “all” trials, selective search was eliminated. The analysis compared the Only effect and intrusion data under these two conditions and examined the fate of to-be-forgotten (TBF) recall on “all” trials. The evidence confirmed the major role of selective search in producing the Only effect. It was concluded that if a pretest mechanism was operative, it did not have the properties of a voluntary forgetting mechanism and it had only a small effect on the first half of the list.     

Believe in yourself: Manipulating beliefs about memory causes checking

One of the most common compulsions in obsessive–compulsive disorder (OCD) is repeated checking. Although individuals often report that they check to become more certain, checking has been shown to have the opposite effect – increased checking causes increased uncertainty. However, checking may also be thought of as beginning because of memory uncertainty. Beliefs about responsibility, over-estimation of threat, intolerance of uncertainty, perfectionism, and importance of and control of thoughts are already known to affect different aspects of OCD symptomatology. Beliefs about memory, however, are not currently considered to influence compulsive behaviour. In the current study, beliefs about memory were manipulated to test whether or not they affected urges to check. Ninety-one undergraduate participants received (positive or negative) false feedback about their performance on aspects of a standardized memory test, and then completed two additional memory tasks. Their urges to check following these tasks were assessed. Consistent with our hypotheses, individuals in the low memory confidence condition had greater urges to check following the memory tasks than those in the high memory confidence condition, demonstrating that manipulations of beliefs about memory can influence checking. Results and implications are discussed in terms of cognitive-behavioural models of and treatments for OCD.     

Age Differences in the Distractor-Ratio Effect as a Function of Contrast Level

ABSTRACT

Latencies (RT) and eye movement measures were used to examine the effects of age and contrast on the distractor-ratio effect (DRE) in visual search. Younger and older adults performed a contrast × orientation conjunction search task where the ratios of white to black distractors and luminance contrast levels were varied. The distractor-ratio manipulation had similar effects for older and younger adults on both RT and the number of fixations required to find the target. Both measures were largely independent of distractor ratio on target-present trials, while both RTs and the fixation number increased with the number of items sharing the target's contrast polarity on target-absent trials. A more detailed analysis of eye movements suggested that younger adults were a bit more adept at attending to the smaller set of distractors, which presumably facilitated both overt and covert search. Generalized slowing can account for the age differences in RT, but the fixation number data speak to another mechanism, perhaps increased cautiousness on the part of the elderly when signal strength is low.     

Increased experience amplifies the activation of task-irrelevant category representations

Prior research has demonstrated the benefits (i.e., task-relevant attentional selection) and costs (i.e., task-irrelevant attentional capture) of prior knowledge on search for an individual target or multiple targets from a category. This study investigated whether the level of experience with particular categories predicts the degree of task-relevant and task-irrelevant activation of item and category representations. Adults with varying levels of dieting experience (measured via 3 subscales of Disinhibition, Restraint, Hunger; Stunkard & Messick, Journal of Psychosomatic Research, 29(1), 71–83, 1985) searched for targets defined as either a specific food item (e.g., carrots), or a category (i.e., any healthy or unhealthy food item). Apart from the target-present trials, in the target-absent “foil” trials, when searching for a specific item (e.g., carrots), irrelevant items from the target’s category (e.g., squash) were presented. The ERP (N2pc) results revealed that the activation of task-relevant representations (measured via Exemplar and Category N2pc amplitudes) did not differ based on the degree of experience. Critically, however, increased dieting experience, as revealed by lower Disinhibition scores, predicted activation of task-irrelevant representations (i.e., attentional capture of foils from the target item category). Our results suggest that increased experience with particular categories encourages the rapid activation of category representations even when category information is task irrelevant, and that the N2pc in foil trials could potentially serve as an indication of experience level in future studies on categorization.     

Repeated checking really does cause memory distrust

Memory phenomena associated with obsessive-compulsive disorder (OCD) have received increased attention in the recent literature. Some debate remains about whether OCD is characterized by deficits in memory per se, or by poor memory confidence. Following from a recent study that demonstrated memory distrust results from repeated checking of a virtual computerized stove, we asked 50 undergraduate students to repeatedly turn on, turn off and check either a real kitchen stove (relevant checking) or a real kitchen faucet (irrelevant checking) in a standardized, ritualized manner. All participants completed a final check of the stove following these 19 checking trials. Results indicated that following repeated relevant checking, participants reported significantly reduced memory confidence, vividness and detail. Repeated irrelevant checking did not produce these decreases. Results are discussed in terms of cognitive-behavioural formulations of OCD and in terms of the effects of repetition on memory and metamemory.     

The effects of local prevalence and explicit expectations on search termination times

In visual search tasks, the relative proportions of target-present and -absent trials have important effects on behavior. Miss error rates rise as target prevalence decreases (Wolfe, Horowitz, & Kenner, Nature 435, 439-440, 2005). At the same time, search termination times on target-absent trials become shorter (Wolfe & Van Wert, Current Biology 20, 121-124, 2010). These effects must depend on some implicit or explicit knowledge of the current prevalence. What is the nature of that knowledge? In Experiment 1, we conducted visual search tasks at three levels of prevalence (6%, 50%, and 94%) and analyzed performance as a function of "local prevalence," the prevalence over the last n trials. The results replicated the usual effects of overall prevalence but revealed only weak or absent effects of local prevalence. In Experiment 2, the overall prevalence in a block of trials was 20%, 50%, or 80%. However, a 100%-valid cue informed observers of the prevalence on the next trial. These explicit cues had a modest effect on target-absent RTs, but explicit expectation could not explain the full prevalence effect. We conclude that observers predict prevalence on the basis of an assessment of a relatively long prior history. Each trial contributes a small amount to that assessment, and this can be modulated but not overruled by explicit instruction.     

Examination of emotional Stroop interference in obsessive-compulsive disorder

Previous research has produced conflicting findings on whether or not patients with subclinical or manifest obsessive-compulsive disorder (OCD) share an attentional bias for anxiety-related material. In the present study, 35 OCD patients were compared with 20 healthy controls on their performance in an emotional Stroop paradigm. Nine different stimulus conditions were compiled, including sets for depression-related and anxiety-related words as well as stimuli from two constructs with a potential relevance for the pathogenesis and maintenance of OCD symptomatology: responsibility and conscientiousness. Patients did not show enhanced interference for any of the conditions. Syndrome subtype and severity, avoidance and speed of information processing did not moderate results. The present study concurs with most prior research that OCD patients display no interference effect for general threat words. It deserves further consideration, that emotional interference effects in OCD as seen in other anxiety disorders occur when using idiosyncratic word material with a direct relation to the individual's primary concerns.