Departures from sensible play in computer blackjack.

Gambling has been viewed as irrational, and even though blackjack offers rational strategies (i.e., Basic [E. Thorp, 1966] and card counting), people exhibit departures from rationality (e.g., "Never Bust" strategies). To determine whether departures from rational behavior reflect ignorance or fatigue, university students were provided with on-line Basic advice while playing a simplified computer blackjack. Although the on-line advice initially affected the totals these players sat on, it was eventually discarded for higher risk strategies. Irrational play did not reflect ignorance or fatigue and was not necessarily conservative. Real fluctuations of odds in blackjack may lead to situations in which Basic is not perceived by players as effective. Because Basic is not a personalized strategy, it seems less likely to be maintained in the face of losses. Players were more optimistic that they might win when utilizing their personalized strategies.

Segregation by color and stereoscopic depth in three-dimensional visual space.

Two experiments were conducted to investigate how color and stereoscopic depth information are used to segregate objects for visual search in three-dimensional (3-D) visual space. Eight observers were asked to indicate the alphanumeric category (letter or digit) of the target which had its unique color and unique depth plane. In Experiment 1, distractors sharing a common depth plane or a common color appeared in spatial contiguity in the xy plane. The results suggest that visual search for the target involves examination of kernels formed by homogeneous items sharing the same color and depth. In Experiment 2, the xy contiguity of distractors sharing a common color or a common depth plane was varied. The results showed that when target-distractor distinction becomes more difficult on one dimension, the other dimension becomes more important in performing visual search, as indicated by a larger effect on search time. This suggests that observers can make optimal use of the information available. Finally, color had a larger effect on search time than did stereoscopic depth. Overall, the results support models of visual processing which maintain that perceptual segregation and selective attention are determined by similarity among objects in 3-D visual space on both spatial and nonspatial stimulus dimensions.

Pilot performance with blood alcohol concentrations below 0.04%.

The effects of a low (less than 0.04%) BAC on pilot performance were investigated in a series of four experiments in which pilots flew a light aircraft simulator under alcohol and placebo conditions. The mean BACs of subjects when starting and finishing the test sessions were 0.037% and 0.028%, respectively. Two of the experiments involved demanding flight tasks under instrument meteorological conditions: complicated departure, holding, and approach procedures in one case; and VOR-use intersection problems in the other. The other two experiments involved ILS approaches under turbulence, cross wind, and simulated wind shear conditions that imposed heavy control-task loads on the pilots. Significant alcohol effects were found, but only under the heaviest workload conditions. During posttest interviews 75% of the pilots reported physical and/or mental effects due to alcohol.

Visuo-spatial processing in parkinsonians.

It has been suggested that patients with Parkinson's disease (PDs) may have problems processing visuo-spatial information and that this deficiency may contribute to the motor control problems observed in PD. However, most studies reporting visuo-spatial deficits are equivocal; they confound perceptual and motor processes. To address this issue, the present experiment systematically compared the relative contributions of several cognitive processes to performance: perception, stimulus-response translation, movement preparation and execution. Seven non-demented PDs and seven age-matched controls performed visual RT tasks, based upon judgements of spatial displacements. Both the RT and MT data suggested that PDs do not prepare movements as adequately as normals, and that PD deficits are associated with problems controlling movement execution. On the other hand, PDs were not slower in judging distances and linking perception to action, suggesting that previous findings of visuo-spatial deficits may be due in part to motor impairments.