122 JOURNAL OF COSMETIC SCIENCE i i _ Bare fingers Lpøet•3or•eu m jelly 0 20 40 60 80 100 120 140 TIME seconds Figure 4. Self-applied time-intensity evaluations of the lotion product, petroleum jelly product, and bare-fingers rubbing motions. Mean values at each sample time are indicated along with the 95 % confidence intervals for the mean. This study also suggests that "soothing" intensity has both a tactile and psychological (hedonic) component. For example, one could say that the self-applied samples were perceived as more soothing due to the additional tactile information provided by the subject's own fingers. However, "soothing" overall also has a hedonic aspect in that the quantification of "soothing" depends on the subject's psychological assessment in ad- dition to the processing of tactile information. The term soothing was not specifically defined for the subjects in this study. The error bars around the product ratings suggest that the subjects were using a similar definition. General sources of variance would include the following: 1) variable skin pressure during the rubbing process (both self- and other-applied) 2) variable conditions as to where the applied products were at any time (for example, on the skin versus between fingers) 3) variable subject-to-subject skin properties 4) differences in "soothing" calibration, re- flecting to some extent different backgrounds in "soothing" experiences and 5) the precision of a given rating, reflected in a given subject's ability to determine: a) the absolute intensity at any time, and b) the transition points, i.e., when a "4" decreases to a "3," etc. In this study, subjects were restricted to whole numbers no fractions were allowed. Sample variance (regarding the lotion and petroleum jelly) was probably

TIME-INTENSITY "SOOTHING" EVALUATION 123 m (.9 m 0 0 --•-- Bare fingers • Lotion :••. ••.• --•-- Petroleum jelly 20 40 60 80 100 120 140 TIME seconds Figure 5. Other-applied time-intensity evaluations of the lotion product, petroleum jelly, and bare-fingers rubbing motions. Mean values at each sample time are indicated along with the 95% confidence intervals for the mean. insignificant, although the amount of sample applied per evaluation may have varied somewhat. This study did not specifically address why there would be a decreasing behavior with time. It is possible that this decrease is due to one or more of the following: 1) pure sensory adaptation behavior (fatigue) 2) mental fatigue 3) changing physical properties of the product during the rubbing process or 4) changing skin conditions as a result of the rubbing process. It should be noted that the third possible explanation would not apply to the bare-fingers evaluation. Also, it is likely that a higher degree of skin irritation (relative to the two product samples) was experienced by subjects during the bare-fingers rubbing motions, although this was not quantitated by visual or instru- mental means. It has been speculated that some skin-care products such as cleansers may induce skin redness, dryness, and roughness as a result of the modification of components of the stratum corneum and/or the interaction with cells of the deeper skin layers after penetration (7). The extent to which this occurred (if it did at all) with the two product samples was not determined. Tactile responses are important to the evaluation of skin lotions and creams. The