Assessment of age at death by microscopy: unbiased quantification of secondary osteons in femoral cross sections

The microscopic method of age at death determination was introduced by Kerley in 1965 [E.R. Kerley, The microscopic determination of age in human bone, Am. J. Phys. Anthropol, 23 (1965) 149-163.]. However, even though the method has been revised several times, there remain some fundamental issues concerning the reliability of the methods. This is because several basic histological features seen in a cross section of a bone have to be quantified according to the method, but the definition, and hence quantification, of these features leaves room for subjectivity. In a previous study we found that some of these features (osteon fragments and Haversian canals) could not be identified reliably. Only secondary osteons could be identified with a low inter and intra observer error. Furthermore, since the histological features are quantified in only parts of an entire bone cross section, the selection of these parts or areas is a potential source of bias. Finally, unless an unbiased method is used for addressing features on the borders of the selected areas, this will also introduce error. These issues have not been addressed specifically in previous studies. In this study, we used the methods of stereology to choose the regions of interest, as well as for dealing with border phenomena, and we only counted secondary osteons. Our results show a statistically significant increase in the median number of osteons per area unit with increasing age at death. However, this was after exclusion of one outlier. This result is probably due to the limited sample size (N = 24). As such, this study is preliminary, but does warrant applying the described techniques to a larger sample.     

Experiencing impartiality to invoke fairness in the n-PD: Some experimental results

Subjects play a 5-person Prisoner's Dilemma both from an impartial point of view and in a regular fashion to determine whether 1) Concerns for fairness increase cooperative behavior; 2) Play of a Prisoner's Dilemma from an impartial point of view results in significantly higher levels of cooperation than does normal play; 3) Concern for fairness has greater explanatory force in explaining cooperation in impartial plays of the Prisoner's Dilemma than in normal plays; and 4) Experience with impartial play of a Prisoner's Dilemma sensitizes subjects to normative imperatives and results in higher levels of cooperation in subsequent normal plays of Prisoner's Dilemmas. The first and second hypotheses are supported, the third is inverted, and the fourth is not supported. Concern for fairness is demonstrated to play a complex role in explaining cooperative behavior in regular plays of the game. An earlier version was presented at the Annual meetings of the Public Choice Society, 1993 Monteleone Hotel, New Orleans; 20 March 1993.