Robert C. Radtke

Dopamine Receptor (DRD2) Genotype-Dependent Effects of Nicotine on Attention and Distraction During Rapid Visual Information Processing

The effects of nicotine, distractor type, and dopamine type-2 receptor (DRD2) genotype on rapid visual information processing (RVIP) task performance were assessed in habitual smokers. Four RVIP tasks differed in terms of distractor location (central vs. peripheral) and distractor type (numeric vs. emotional). Each participant performed each of the tasks on two different days, once while wearing an active nicotine patch and once while wearing a placebo patch. Overall, the nicotine patch produced more accurate detection of and faster reaction times to target sequences; however, these effects varied with distractor type and genotype. Nicotine speeded reaction time more with left-visual-field (LVF) than right-visual-field (RVF) emotional distractors but speeded reaction time more with RVF than LVF numeric distractors, especially when the distractor digit matched the target sequence in terms of numeric oddness or evenness. Nicotine tended to facilitate performance more in individuals with at least one A1 allele than in homozygous A2A2 individuals, especially with numeric distractors presented to the left hemisphere. Nicotine tended to reduce distraction by negative stimuli more than other types of stimuli. Few gender differences were observed. The overall pattern of results was consistent with the view that nicotine modulates selective attention or subsequent information processing in a manner that depends partly on the emotional versus numeric nature of task distractors, DRD2 genotype, and the brain hemisphere that initially processes the distractors (visual field of distractor).

Effects of nicotine on brain responses to emotional pictures

Given that nicotine reduces negative affect, one would expect nicotine to have different effects on brain responses to emotionally negative stimuli than it does on responses to emotionally neutral or positive stimuli. However, no studies have assessed this possibility. The present study assessed the effects of nicotine patch versus placebo patch on brain event-related potential (ERP) responses to emotion-inducing negative, positive, and neutral color pictures in 16 smokers in a double-blind, counterbalanced, within-subjects design. The study included four experimental sessions. After overnight smoking deprivation (12 hr or more), active nicotine patches were applied to participants during one of the first two sessions and during one of the last two sessions. Placebo patches were applied during the other two sessions. Nicotine reduced frontal ERP processing voltage negativity (from 144-488 ms poststimulus onset) evoked by viewing emotionally negative pictures to a greater extent than it did when emotionally neutral pictures were viewed, whereas it had no effect on processing negativity evoked by positive pictures. Nicotine also enhanced P390 amplitudes evoked by emotionally negative pictures more than it did when emotionally neutral and positive pictures were viewed. Across picture types, nicotine (relative to placebo) reduced N300 amplitude (more at anterior and dorsal sites) and increased P390 amplitude. Overall, nicotine influenced ERPs to emotionally neutral and positive pictures less than it did to negative pictures.

Nicotine decreases attentional bias to negative-affect-related Stroop words among smokers.

The present study examined the hypothesis that nicotine is associated with reduced attentional bias to affective and smoking-related stimuli in a modified Stroop task. A total of 56 habitual smokers were each tested on 4 days with 14 mg nicotine patches and placebo patches, counterbalanced, as a within-subjects factor in a double-blind design. A modified Stroop using negative-affect words, smoking words, color words, and neutral words was presented via computer in blocked format. As predicted, nicotine, relative to placebo, was associated with decreased attentional bias to negative words. Nicotine speeded performance during smoking-word and color-word blocks to the same degree as during neutral words and thus appeared to also have a nonspecific performance-enhancing effect. In an exploratory analysis, nicotine-attention effects occurred only in the initial presentation of pairs of blocked word pages. Nicotine also was associated with improved mood. The results are discussed in terms of affect-attention and smoking literatures.

Number of alternatives and similarity in verbal-discrimination learning

Lists of 16 two-alternative (2-A) or four-alternative (4-A) verbal-discrimination items of either low similarity (LS), high within-item similarity (WIS), or high between-item similarity (BIS) were learned by 144 S s. When biases that favored 2-A lists were removed, fewer errors occurred in learning 4-A lists than 2-A lists. More errors occurred in BIS than LS lists with WIS producing an intermediate number of errors. Recognition and recall measures taken after learning revealed better retention of incorrect alternatives from 2-A lists than from 4-A lists, and better retention of WIS items than of BIS or LS items. The results were interpreted in terms of a frequency theory of verbal-discrimination learning.

Reading too much between the lines : illusory correlation and the word association implications test

Abstract We examined the illusory correlation phenomenon with the Word Association Implications Test (WAIT), a task where diagnoses and signs are causally connected due to priming effects. The WAIT is an analogue to clinical assessments in which subjects “read between the lines” of target persons’ word associations which have been primed by fantasized scripts. 164 undergraduates were randomly assigned to study WAIT protocols with either 0, 30, 70, or 100% of the targets veridically identified. Following subjects’ examination of WAIT protocols, we assessed their incidental learning of valid diagnostic clues (i.e., their clue schemata). Subjects given no veridical diagnoses showed minimal incidental learning. However, those given 30, 70, and 100% veridical diagnoses showed equivalent incidental learning of diagnostic clues and all exceeded an intuition (no experience) comparison group. The results suggested that an illusory correlation operated even when clues and diagnoses have causal, not just contingent, connection. Successful judges must contend not only with others’ tools for avoiding prediction but with their own tendencies to read too much between the lines.

Pronunciation and number of alternatives in verbal-discrimination learning

Sixteen item lists in which half of the items were two-alternative and half were four-alternative items were presented to S s in a study-test verbal-discrimination paradigm. On study trials S s in one condition overtly pronounced two-alternative items twice and four alternative items once, and then pronounced the correct alternative once when it was indicated. In another condition no overt pronunciation was required. Four-alternative items were learned faster and with fewer errors than two-alternative items, and there was no significant effect of or interactions with pronunciation. The results were discussed in terms of a relative frequency discrimination theory of verbal discrimination learning.