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Notizen: Previous demonstrations of monetary incentive effects on heart rate during a continuous motor task were extended by employing different magnitudes of incentive: 0¢ (feedback only), 2¢, and 5¢ per response. The influence of the total amount of monetary incentive for the experiment was examined by providing monetary incentives either for only 2 trials or for all 5 trials. This procedure also provided an evaluation of the effect on heart rate during the later trials of discontinuing the incentive after 2 trials. The results showed a clear and graded effect of the amount of incentive per response, but no significant effects were obtained for the total amount of incentive, in spite of providing subjects with clear feedback as to how much money they could expect. Discontinuing incentives produced a significant decrease in heart rate, compared to subjects who continued to receive incentives.No effect was found for the magnitude of incentive on the rate of responding on the motor task, rendering unlikely an explanation for the results in terms of cardiac-somatic coupling. Also, any possible contribution to the heart rate results from frustrative nonreward feedback was eliminated by avoiding any suggestion of failure feedback on the task. It was concluded that the effects are attributable to the incentive value of the monetary reward and that they are large enough to be of considerable interest.

Notizen: Two experiments are reported which test the hypothesis that heart rate increases will be seen in response to monetary incentives during performance on a continuous motor task. In the first study, heart rate was significantly higher when subjects were paid 2ø for each success feedback compared to subjects who received feedback only. In contrast, there was no effect of varying the probability of success (10% versus 90% success). Study 2 replicated the monetary incentive effect on heart rate, this time employing 100% success feedback. In neither study were subjects' response rates significantly affected by monetary incentive. In addition, control groups responding much faster on the task as a result of making it more predictable did not show increased heart rate. Consequently, these incentive effects are difficult to explain with a cardiac-somatic coupling interpretation. It was concluded that cardiac acceleration does occur in response to monetary incentives, even in the absence of failure feedback, and it was proposed that this incentive effect reflects the activation of an appetitive motivational system. Possible applications of the assessment of appetitive responses are suggested.

Notizen: Abstract Two spectrophotometric assays for protein commonly used in marine research (Coomassie stain, “Bradford”; alkaline copper, “Lowry”) and a more recent assay which has not been applied in this field (bicinchoninic acid, “Smith”) were compared for homogenates of the marine diatom Thalassiosira pseudonona using bovine serum albumin (BSA) as a standard. When homogenates were prepared by precipitating protein with trichloroacetic acid (TCA) and redissolving in 1 N NaOH, the protein content estimated by the Lowry and Smith assays agreed closely, but was consistently 20% higher than that indicated by the Bradford assay. To determine if this difference was due to the choice of a protein standard, protein from T. pseudonana was purified and compared to BSA, bovine gamma-globulin (BGG), and casein. The reactivity of the purified protein (expressed as the slope of the absorbance vs protein concentration curve) did not differ between cultures grown at high or low irradiance. For the Smith and Bradford assays the reactivity of BSA was not significantly different from algal protein, but for the Lowry assay, algal protein was significantly higher in reactivity than BSA. BGG was not significantly different in reactivity from algal protein for the Lowry and Smith assays, but BGG gave significantly lower absorbances than algal protein in the Bradford assay. These results suggest that BSA is a suitable standard for algal protein in the Bradford assays, while BGG is preferable for the Lowry assay. Either protein standard could be used for the Smith assay. Differences in purified algal protein reactivity compared to BSA could not account for the differences among the assays, nor could interference by chlorophyll a. Precipitating protein with TCA prior to analyses gave lower protein than direct analyses of homogenates for the Lowry and Smith assays, but no differences were found for the Bradford assay. As a result, the Lowry and Smith assays indicated up to 60% greater protein than the Bradford if TCA precipitation was not performed. This may be due to removal of free amino acids and small peptides which are less reactive in the Bradford assay. The 20% higher protein found in the Lowry or Smith vs Bradford assays may be due to different assay sensitivity to small peptides or other compounds which are precipitated along with proteins by TCA. Although the Smith assay is substantially simpler to perform than the Lowry, there appear to be no quantitative differences in the results. It remains unclear which spectrophotometric assay is most accurate, but the Bradford assay is faster and simpler, and is less likely to be affected by non-protein compounds found in marine phytoplankton.