Devaluation of Pavlovian conditioning in the 10-day-old rat

This experiment established that for the infant rat, 10 days postpartum, a preference conditioned to an olfactory stimulus (conditioned stimulus) could be substantially-decreased-by subsequently lowering the value of the unconditioned stimulus (heat). This devaluation effect disappeared when a sufficiently long interval elapsed between the devaluation treatment and the test, despite maintained retention of the original conditioned preference over this same interval. This suggests that devaluation in infant rats does not permanently change the animal’s original representation of the unconditioned stimulus, but instead may replace it temporarily with a conflicting representation.     

Preexposure to feeding-related stimuli reduces neophobia

Rats that were preexposed to novel solutions or to novel feeding environments showed reduced neophobic responses when presented with a familiar solution in a novel container or with a novel flavored solution in a familiar container, respectively. Preexposure to novel solutions also appeared to reduce emotional reactivity as measured in the open field.     

Conditioned aversion is promoted by memory of CS−

Five experiments tested the effects of experience with a white compartment not paired with footshock (CS?) on conditioning of an aversion to a black compartment paired with footshock. As previously found with odors as CSs, a single pairing of the CS+ with footshock yielded significant conditioning only if the animal was also exposed to CS?, with greater conditioning when the CS? exposure preceded the CS+ than when the CS+ preceded the CS?. If, however, the CS? preceded CS+ by a 24-h interval, it was ineffective and no CS+ conditioning occurred. For adult rats, the effectiveness of the CS?/CS+ “integration” progressively decreased with increasing length of the interval separating their occurrence, although it was still significant (i.e., some CS+ conditioning occurred) with a 12-h CS? to CS+ delay. For preweanlings (16 days postnatal), no conditioning to CS+ occurred if the interval between CS? and CS+ was 1 h or longer, although significant conditioning to CS+ did occur with a CS? to CS+ interval as long as 40 min. It was as if active memory for the CS? at the time of CS+ exposure was necessary for CS+ conditioning, and forgetting of the CS? memory proceeded more rapidly for preweanling than for adult rats. Collectively, these experiments extend results previously indicating that (1) the CS+ contiguous to the US may or may not be “selected” for conditioning, depending on the rat’s exposure to, or memory for, a CS?, and (2) this stimulus selection might differ for immature and mature rats.     

中国金丝桃属金丝桃组(藤黄科)新分类群

描述了中国云南北部的金丝桃属Hypericum L.(藤黄科)两个新种,即楚雄金丝桃H. fosteri N. Robson和漾濞金丝桃H. wardianum N. Robson。二者均与短柱金丝桃H. hookerianum Wight &; Arn.相近。楚雄金丝桃为一地方特有种,目前仅在模式地点发现;漾濞金丝桃在缅甸东北部还有分布。二者主要以蒴果伸长,非卵状近球形,萼片无中脉而有别于短柱金丝桃。此外,将宽萼金丝桃H. latisepalum (N. Robson) N. Robson从亚种提升为种;将变异较大的纤枝金丝桃H. lagarocladum N. Robson划分为两个亚种,即叶较宽、具有开张习性的原亚种纤枝金丝桃H. lagarocladum ssp. lagarocladum和叶较窄、更为直立的新亚种狭叶金丝桃H. lagarocladum ssp. angustifolium N. Robson。     

The natural sciences: Trouble ahead? Yes

This essay expands a talk given by Professor Gross at the annual meeting of the American Academy for Liberal Education, held at St. John’s College, Santa Fe, New Mexico, October 29–30, 1993.     

Development and evaluation of the conceptual inventory of natural selection

Natural selection as a mechanism of evolution is a central concept in biology; yet, most nonbiology‐majors do not thoroughly understand the theory even after instruction. Many alternative conceptions on this topic have been identified, indicating that the job of the instructor is a difficult one. This article presents a new diagnostic test to assess students' understanding of natural selection. The test items are based on actual scientific studies of natural selection, whereas previous tests have employed hypothetical situations that were often misleading or oversimplified. The Conceptual Inventory of Natural Selection (CINS) is a 20‐item multiple choice test that employs common alternative conceptions as distractors. An original 12‐item version of the test was field‐tested with 170 nonmajors in 6 classes and 43 biology majors in 1 class at 3 community colleges. The test scores of one subset of nonmajors (n = 7) were compared with the students' performances in semistructured interviews. There was a positive correlation between the test scores and the interview scores. The current 20‐item version of the CINS was field‐tested with 206 students in a nonmajors' general biology course. The face validity, internal validity, reliability, and readability of the CINS are discussed. Results indicate that the CINS will be a valuable tool for instructors. © 2002 Wiley Periodicals, Inc. J Res Sci Teach 39: 952–978, 2002