Acute alcohol intoxication impairs controlled search across the visual field.

OBJECTIVE: The objective of the two experiments reported was to examine the effects of acute alcohol intoxication and of alcohol expectancies on controlled search across the visual field. METHOD: After receiving an oral dose of 0.5 g/kg alcohol (Experiment 1), an oral dose of 0.7 g/kg alcohol (Experiment 2), or a placebo, participants searched for a target in large arrays of homogeneous distractors that were either highly similar or less similar to the target. Targets were systematically placed at fixation and at visual angles of 2.5 degrees , 5.0 degrees , 7.5 degrees , and 10.0 degrees . RESULTS: Target detection was less accurate in the placebo condition of both experiments than in the no-beverage control group, suggesting that alcohol expectancies had a negative effect on controlled search. The effects of alcohol at the lower dose and of the placebo on visual search were not different (Experiment 1). At the higher dose, the negative effects of target eccentricity on the accuracy of target detection were larger when targets appeared among highly similar distractors, compared with the placebo condition and with a no-beverage control group. Target eccentricity effects on accuracy or speed were not observed at either dose when targets and distractors were dissimilar. CONCLUSIONS: Acute alcohol intoxication at either a low or high dose and placebo-associated intoxication expectancies have a detrimental effect on controlled visual search in large arrays. Acute alcohol intoxication at a high dosage exaggerates the detrimental effects of target eccentricity and of task difficulty on controlled visual search.

Modeling age-related memory deficits: a two-parameter solution.

Recent research and meta-analytic reviews suggest that 1 observed pattern of impaired and intact memory performance with advancing age is a deficit in measures of episodic but not semantic memory. The authors used computational modeling to explore a number of age-related parameters to account for this pattern. A 2-parameter solution based on lifelong experience successfully fit the pattern of results in 5 published studies of the word-frequency mirror effect and paired-associate recognition. Lifelong experience increases the strength (resting level of activation) of concepts in the network but also saturates the network with an increasing number of episodic associations to each concept. More episodic associations to each concept mean that activation spreads more diffusely, making retrieval of any newly established memory trace less likely; however, the greater strength of a concept makes recognition based on familiarity more likely. The simulations provide good quantitative fits to the extant age-related memory literature and support the plausibility of this mechanistic account.