Coarse guidance by numerosity in visual search

In five experiments, we examined whether the number of items can guide visual focal attention. Observers searched for the target area with the largest (or smallest) number of dots (squares in Experiment 4 and “checkerboards” in Experiment 5) among distractor areas with a smaller (or larger) number of dots. Results of Experiments 1 and 2 show that search efficiency is determined by target to distractor dot ratios. In searches where target items contained more dots than did distractor items, ratios over 1.5:1 yielded efficient search. Searches for targets where target items contained fewer dots than distractor items were harder. Here, ratios needed to be lower than 1:2 to yield efficient search. When the areas of the dots and of the squares containing them were fixed, as they were in Experiments 1 and 2, dot density and total dot area increased as dot number increased. Experiment 3 removed the density and area cues by allowing dot size and total dot area to vary. This produced a marked decline in search performance. Efficient search now required ratios of above 3:1 or below 1:3. By using more realistic and isoluminant stimuli, Experiments 4 and 5 show that guidance by numerosity is fragile. As is found with other features that guide focal attention (e.g., color, orientation, size), the numerosity differences that are able to guide attention by bottom-up signals are much coarser than the differences that can be detected in attended stimuli.     

Retrieval-induced forgetting and unwanted thought intrusions

The act of retrieving an existing memory has been found to inhibit the recall of related memories, a phenomenon known as retrieval-induced forgetting (RIF). The purpose of the present study was to investigate the hypothesis that individuals with a strong RIF effect might be better at suppressing unwanted intrusive thoughts. In Experiment 1 the relationship between RIF and the prevalence of intrusive thoughts was investigated using a sample of 58 normal British participants, who completed three different questionnaires to measure their susceptibility to intrusive thoughts, obsessional thoughts, and impulsive thoughts. Their susceptibility to RIF was also measured, using the standard procedure introduced by Anderson, Bjork, and Bjork (1994). The results showed a significant RIF effect, and, although no significant correlations were found between RIF strength and any of the three measures of intrusive thoughts, there was some evidence to suggest a possible relationship between RIF and intrusive thoughts. In an effort to clarify these inconclusive findings, Experiment 2 investigated the relationship between RIF and intrusive thoughts in a different and more varied population sample, consisting of 90 normal members of the Greek population. Experiment 2 confirmed the RIF effect, but no significant association was found between RIF and intrusive thoughts. These findings therefore offer no support for the hypothesis that RIF assists the suppression of intrusive thoughts in normal individuals.     

Disturbances of consciousness in dementia with Lewy bodies associated with alteration in nicotinic receptor binding in the temporal cortex

Disturbances of consciousness, including fluctuations in attention and awareness, are a common and clinically important symptom in dementia with Lewy bodies (DLB). In the present study we investigate potential mechanisms of such disturbances of consciousness (DOC) in a clinicopathological study evaluating specific components of the cholinergic system. [3H]Epibatidine binding to the high-affinity nicotinic receptor in the temporal cortex (Brodmann's areas 20 and 36) differentiated DLB cases with and without DOC, being 62-66% higher in those with DOC (F=4.5,p=.025). The were no differences between DLB patients with or without DOC in 125I-labeled alpha-bungaratoxin binding to the low-affinity nicotinic receptor, [3H]pirenzepine binding to the muscarinic M1 receptor, or in choline acetyltransferase activity. These findings provide support for the hypothesis that cholinergic activity is an important neural correlate if consciousness and suggest a mechanism of DOC in DLB involving alterations in the nicotinic receptor, composed of predominantly alpha4 and beta2 subunits.     

Loving the One You Hurt: Positive Effects of Recounting a Transgression against an Intimate Partner

Intimate partners described a past transgression in which one of them had been a victim and the other a perpetrator and then evaluated each other and their relationship. Participants had been randomly assigned to the perpetrator or victim role. Perpetrators described their actions as more justifiable, perceived greater improvement since the transgression, and were more optimistic about the future of their relationship than were their victims or control participants. The results support the authors' contention that temporal appraisals are an important mechanism enabling people to maintain positive images of themselves and their relationships.     

Metabolic control and auditory information processing at altered glucose levels in insulin-dependent diabetes

Previous work with a visual reaction time (RT) paradigm showed rate of mental processing to be slowed during a state of brain energy depletion (i.e., hypoglycemia). The present study employed an analog auditory RT paradigm to determine if modality differences in processing information might occur in response to glucose alteration. A balanced crossover design was used in which men with insulin-dependent diabetes completed RT tasks of increasing complexity at each of the following glucose levels: hypoglycemia (60 mg/dL), normoglycemia/control (110 mg/dL), and hyperglycemia (300 mg/dL). Results revealed two performance groups. A convergent group displayed slower RT responding during hypoglycemia, consistent with the visual RT pattern of results. A divergent group displayed better responding on one RT measure during hypoglycemia, and generally poorer responding on all RT measures during the other glucose conditions. Subjects in the divergent group maintained more stringent metabolic control and tended to have experienced more episodes of hypoglycemic unconsciousness. The present results provide the first evidence that more stringent metabolic control may be related to generally slower rates of processing auditory information. Possible explanations for these findings include hypotheses of immutable structual derangement, state-dependent performance effects, and a U-shaped response curve.     

Motivational pathways underlying the onset and maintenance of viewing child pornography on the Internet

The staggering rate at which incidents of child pornography (CP) are increasing highlights the need for proactive approaches to this problem. Improving the efficacy and accessibility of interventions designed for individuals who view CP provides one means of addressing this growing concern. This article explores the self-identified motivations underlying the onset and maintenance of viewing Internet-based CP among a sample of 20 men receiving treatment for this behavior. Our findings suggest two primary motivational pathways, namely a desire to achieve sexual gratification and/or an attempt to avoid emotional pain. We propose a behavioral facilitation process, initiated by extensive exposure to Internet pornography, to explain the use of CP in men without a sexual interest in children. We also discuss factors that appeared to facilitate the maintenance of this behavior. Our findings indicate that social skills deficits, maladaptive coping strategies, and a lack of sexual education require further investigation regarding their role in promoting or precluding desistance from viewing CP.     

Why are there eccentricity effects in visual search? Visual and attentional hypotheses

In standard visual search experiments, observers search for a target item among distracting items. The locations of target items are generally random within the display and ignored as a factor in data analysis. Previous work has shown that targets presented near fixation are, in fact, found more efficiently than are targets presented at more peripheral locations. This paper proposes that the primary cause of this “eccentricity effect” (Carrasco, Evert, Chang, & Katz, 1995) is an attentional bias that allocates attention preferentially to central items. The first four experiments dealt with the possibility that visual, and not attentional, factors underlie the eccentricity effect. They showed that the eccentricity effect cannot be accounted for by the peripheral reduction in visual sensitivity, peripheral crowding, or cortical magnification. Experiment 5 tested the attention allocation model and also showed that RT X set size effects can be independent of eccentricity effects. Experiment 6 showed that the effective set size in a search task depends, in part, on the eccentricity of the target because observers search from fixation outward.