The variables which are said to affect human temperature sensitivity are the skin temperature, the area of thermal stimulation and the rate at which the temperature of the skin is changed. Of these, the last has been only partially described Hensel (1950) has listed three variables of thermal stimulation which affect the sensitivity of human subjects to warm and cool stimuli. These are the temperature to which the skin has been adapted. the area of skin over which the thermal energy is applied. and the rate at which the temperature of the skin is changed. The first variable. adapted skin temperature, resulted in a large warm and small cool thresholds when the skin had been adapted to low temperatures (29 0C and lower). When the skin had been adapted to high temperatures (37 0C and higher) the warm thresholds were small but the cool thresholds were large (Hensel, 1950;Kenshalo, Nafe. & Brooks. 1961).The second variable, area of stimulation, is inversely related to the intensity of thermal stimulation required to produce threshold warm (Hardy & Oppel, 1937; Kenshalo, Decker, & Hamilton, 1967) and cool (Hardy & Oppel, 1938) sensations.The third variable of human temperature sensitivity, the rate at which the temperature of the skin is changed, is the subject of this investigation. It has received relatively little attention. The facts that are available appear contradictory. When conducted thermal energy was applied to an area of 20 cm 2 on the volar surface of the forearm, Hensel (1950) found that he could change the skin temperature from 29 0C to 36 0C at rates of 0.007 0C/sec or less without producing a thermal sensation. When the rate of temperature change was systematically varied, and starting from normal skin temperature (about 33.5°C). he found that the warm threshold remained relatively constant at rates of warming of O.015 0C/sec and higher. When slower rates of warming were used the warm threshold increased markedly. It is difficult to determine from his data what happened to the cool threshold when various rates of cooling were used, except that at slow rates of cooling. the cool threshold seemed to increase.Non-penetrating radiant energy seems to produce threshold warm sensations at far smaller rates of skin temperature change than those required by conducted thermal energy. Threshold warm sensations have been reported when the rate of increase of skin temperature was only 0.003 0C/sec for a 3 sec exposure (Hardy & Oppel, 1937;Hendler & Hardy, 1960). Cool threshold sensations (produced by exposure to a block of dry ice) occurred when the rate of skin cooling was approximately O.004oC/ sec for a 1 sec exposure (Hardy & Oppel, 1938). For both warm and cool stimulation the area of exposure was larger than 200 cm 2• When smaller areas were exposed, the rate of skin temperature change required to produce a threshold sensation increased. When the area exposed was limited to 23.8 cm 2 of the forehead. the rate of skin temperature change required to produce a threshold warm sensation was +0.017 0C/sec for 3 ...

Swan Point in central Alaska contains the oldest recognized human occupation in Alaska (Cultural Zone 4b [CZ4b]), dating to circa 14,000 cal BP. This component consists of a microblade and burin industry with clear technological ties to the Siberian Upper Paleolithic Diuktai Culture. Through the systematic use of the Yubetsu method for the production of microblades, Swan Point is technologically more similar to Siberian microblade sites than to later-age (Denali complex) microblade sites in Alaska. The Yubetsu method is the hallmark of the Diuktai Culture, and in Alaska, Swan Point CZ4b is the only component with systematic production of microblades using the Yubetsu method. Other late Pleistocene and Holocene microblade sites in Alaska have an industry based on Campus-style, conical, or tabular microblade cores. Analysis of the collection furthers our understanding of how CZ4b relates to previous Siberian Diuktai-related assemblages and to later Alaskan Denali-related sites. We interpret the CZ4b component as representing a brief single event that has major cultural and technological implications for the early colonization process of North America.

We document the use of organic raw material in late Pleistocene eastern Beringia through the study of the site of Swan Point CZ4b, in central Alaska. CZ4b is attributed to the Dyuktai culture and dates to about 14,000 cal B.P. We interpret the occupation as a specialized workshop dedicated to the production and maintenance of organic-based tools following three lines of evidence: (1) limited on-site consumption of megafauna, (2) diversity of organic raw materials and techniques used in processing them, and (3) spatial demarcation of specialized activity areas. Specialized workshops are located in the vicinity of naturally occurring accumulations of mammoth bones in both western and eastern Beringia and suggest similarities in animal resource use across Beringia for the Dyuktai culture. Organic technology was a major portion of Dyuktai technology in eastern Beringia, and its lack of visibility in archaeological assemblages is probably due to taphonomic reasons. Changes in the availability of organic raw material throughout the Late Pleistocene offer some implications for the evolution of lithic technology and material culture.

By 13,000 BP human populations were present across North America, but the exact date of arrival to the continent, especially areas south of the continental ice sheets, remains unclear. Here we examine patterns in the stratigraphic integrity of early North American sites to gain insight into the timing of first colonization. We begin by modeling stratigraphic mixing of multicomponent archaeological sites to identify signatures of stratigraphic integrity in vertical artifact distributions. From those simulations, we develop a statistic we call the Apparent Stratigraphic Integrity Index (ASI), which we apply to pre- and post-13,000 BP archaeological sites north and south of the continental ice sheets. We find that multiple early Beringian sites dating between 13,000 and 14,200 BP show excellent stratigraphic integrity. Clear signs of discrete and minimally disturbed archaeological components do not appear south of the ice sheets until the Clovis period. These results provide support for a relatively late date of human arrival to the Americas.

Eight rat snakes were given 50 paired presentations of light and vibratory stimulation. Ss were tested in a two compartment chamber with a 12 hr. interval between each trial. Moving from one compartment to the other terminated and permitted escape from the vibratory stimulus. Data from two Ss was discarded because of inadequate responsiveness. Except for the terminal block of trials Ss demonstrated a progressive decline in escape time. Individual Ss, however, were highly variable in their performance.