Operational Momentum in Multiplication and Division?

Biases are commonly seen in numerical cognition. The operational momentum (OM) effect shows that responses to addition and subtraction problems are biased in the whole-number direction of the operation. It is not known if this bias exists for other arithmetic operations. To determine whether OM exists in scalar operations, we measured response bias in adults performing symbolic (Arabic digits) and non-symbolic (dots) multiplication and division problems. After seeing two operands, with either a multiplication (×) or division (÷) sign, participants chose among five response choices. Both non-random performance profiles and the significant contribution of both operands in a multiple regression analysis predicting the chosen values, suggest that adults were able to use numerical information to approximate the outcomes in both notations, though they were more accurate on symbolic problems. Performance on non-symbolic problems was influenced by the size of the correct choice relative to alternatives. Reminiscent of the bias in addition and subtraction, we found a significant response bias for non-symbolic problems. Non-symbolic multiplication problems were overestimated and division problems were underestimated. These results indicate that operational momentum is present in non-symbolic multiplication and division. Given the influence of the size of the correct choice relative to alternatives, an interaction between heuristic bias and approximate calculation is possible.     

Dr. Mary Fanning: caring for AIDS patients at Toronto General.

Although amoxicillin has long been the preferred drug for treatment of acute otitis media, resistant strains of two relatively common causal organisms have emerged, prompting a search for other antibiotics. We performed a randomized double-blind trial comparing amoxicillin and trimethoprim-sulfamethoxazole in 221 children in whom acute otitis media was diagnosed in an outpatient setting. Diagnosis was on the basis of symptoms, otoscopic examination and acoustic reflectometry. No culture specimens were taken. A research nurse, using the same methods, evaluated patients in a follow-up home visit at around 14 days and measured compliance by examination of the medicine bottle. Equal proportions of children in the two groups were cured or improved (88% and 87%). Therapeutic efficacy was related to compliance in both groups, and there were few side effects in either group. This study had statistical power of 80% to detect a difference of 15%. We conclude that trimethoprim-sulfamethoxazole can be considered a first-line antibiotic in the treatment of acute otitis media.     

Effects of DL–thyroxine on swimming speed in pearl danio Brachydanio albolineatus (Blyth)

Pearl Danios (Brachydanio albolineatus –Blyth) were allowed four days for acclimation in river-water filled aquaria maintained at a mean temperature of 27° C. A different concentration of DL-thyroxine (T₄) was added to each of two aquaria. A third aquarium served as a control and received no hormone. Photoperiod, feeding, aeration, and observer interference were controlled so as not to influence the results of the study. Mean swimming speeds for the fish in each aquarium were calculated. Data were subjected to analysis of variance and the Student-Newman-Keuls Test. Compared with the control, significant (P < 0.05) increases in swimming speed were found with concentrations of thyroxine in water of 1:4x 10⁶ and 1:1 x 10⁶. The difference in swimming speed between the two hormone-treated groups was not significant. The fact that exogenous thyroxine will increase swimming speed may indicate that endogenous thyroid hormone plays a significant role in such fish behaviour as migration.     

The mechanism of the non-oxidative segment of the pentose cycle in the liver

[1-¹⁴C] Xylitol was used as substrate for isolated liver parenchymal cells from fasted rats or hamsters, and the glucose formed was isolated and degraded. Over 90% of the total radioactivity was in carbons 1 and 3, and the ratio of specific activity of C-1 to that of C-3 was only slightly under two, the expected ratio for the classical mechanism of the non-oxidative pentose phosphate pathway.