Effect of various discriminative stimuli on choice behavior in male siamese fighting fish (Betta splendens).

The current experiment was an exploratory study empirically comparing three discrimination methodologies proposed for use in choice preparations with food rewards. Subjects were thirty-five, healthy, adult male Siamese fighting fish (Betta splendens). Subjects were randomly assigned to one of three discrimination groups: a Direction group (using left or right as discriminative stimuli), a Color group (using red or green as discriminative stimuli), and a Bubble group (using the presence or absence of air bubbles as discriminative stimuli). For all three discrimination groups, subjects chose between one or three food pellets in a submerged T-maze. The results from the experiment indicated a statistically significant preference for the three pellets of food over one pellet of food only for the Bubble group. Of particular note is the effect size and observed power obtained for the Bubble group, which was the only group which supported a reasonably powerful test for discrimination, given a sample size of 12 subjects and 0.94 effect size.

A comparison of four tests of malingering and the effects of coaching.

This study examined the ability of four measures of suboptimal performance to correctly classify four groups of subjects (normal controls, uncoached malingering, coached malingering, and head injured). Only the Portland Digit Recognition Test-Computerized (PDRT-C) identified simulating malingerers with greater than chance accuracy while minimizing false positives. Coached subjects were better able than their uncoached counterparts to avoid detection on all measures. In an additional analysis, a discriminant function using the response latency and total correct scores from the PDRT-C identified 70% of the coached malingerers on cross validation. The three other tests (Nonverbal Forced Choice Test, 21-Item Test, and Dot Counting Test) failed to obtain a satisfactory classification rate for the malingering groups as a whole and coached malingerers in particular.