Adaptation to capsaicin burn: effects of concentration and individual differences.

Human subjects rated the time course of the burn produced by three concentrations of capsaicin applied to the tongue via filter papers. Data were fit to a dynamic model composed of a level detector, a change detector, and a double integrator. These three processes responded differently to concentration. 6-n-Propyl-2-thiouracil (PROP) taster status correlated positively with the integrator process. Although a minority of subjects showed evidence of the integrator process, any subject with an integrator process at a given concentration also showed it at any higher concentration.

Time course of burn to repeated applications of capsaicin.

Human subjects rated the burn of 100 ppm capsaicin applied to the tongue via filter paper and replaced every minute. Capsaicin was presented at a constant concentration for 10 min, followed by 10 min of blank stimuli; this sequence was then repeated once. Both sensitization and desensitization were seen. A dynamic model composed of a level detector and change detector predicted the results and also previous data. Thus, the model provides a parsimonious description of responses to constant and intermittent capsaicin stimulation.

Adaptation to capsaicin within and across days.

Subjects judged the time-course of the burn caused by 100 ppm capsaicin applied to the tongue on Day 1 and Day 5. On Days 2-4, they tasted hard candy containing capsaicin. Most subjects did not show adaptation within Day 1, but either plateaued after about 16 min or rose monotonically for the entire 34 min. Intensity was less on Day 5 and levelled off or declined for most subjects. Data were fit to a mathematical model of adaptation. Adaptation across days was accounted for by changes in the gains of the three processes.

Matrilateral biases in the investment of aunts and uncles : A consequence and measure of paternity uncertainty.

In a study of the kin investment of aunts and uncles we show that the laterality effect expected as a result of paternity uncertainty is statistically reliable but somewhat smaller than the sex effect. Matrilateral aunts invest significantly more than patrilateral aunts, and the same is true for uncles. Regardless of laterality, however, aunts invest significantly more than uncles. Multivariate controls show that the matrilateral bias is fully independent of any age or distance confounds that might result from sex differences in age at marriage or dispersal. We discuss our results in relation to recent findings on the kin investment of grandparents (Euler and Weitzel 1996). In addition, we propose a simple method for estimating the level of paternity uncertainty from kin investment data; application of this method to our data on aunts and uncles suggests that between 13% and 20% of children are not the offspring of their putative father. Our parallel analyses of Euler and Weitzel's (1996) data on grandparental investment suggest a similar estimate, that paternity uncertainty lies between 9% and 17%.

The dissolution of language in Pick's disease with neurofibrillary tangles: a case study.

This paper is a detailed retrospective history of a patient who began to have difficulty with speaking and comprehension in 1967, and whose neuropathological examination at time of death 12 1/2 years later was consistent with a diagnosis of Pick's disease, complicated by neurofibrillary tangles. It follows the deteriorating course of his language abilities in the context of relatively less-impaired general cognitive abilities, using two sources of information. The first is his own written record of his deteriorating abilities, shown in letters and notes he wrote over this period. The second is through an oral history obtained from the patient's family. The purpose of this report is to illustrate in detail the course of a degenerative condition and to suggest the utility of such descriptional records in increasing understanding of language deterioration in dementia.

Temporal properties of the human taste system.

An attempt to apply linear systems methods to the temporal properties of the human taste system is described. The percentage modulation in concentration required to detect a fluctuation in intensity was measured as a function of frequency of modulation. Both a sine-wave and a square-wave input were used. The sensitivity of the taste system at its maximum, and also at the low frequencies, was greater than expected from previous work based on classical methodology. The sensitivity of the taste system at its maximum, and also at the low frequencies, was greater then expected from previous work base on classical methodology. The sensitivity of the taste system to the various qualities was, in decreasing order, salty, sweet, sour, and bitter. The taste system in insensitive to frequencies above about 5 Hz. Except for bitter, representatives of the various taste qualities yielded similar functions within qualities.