Subskill mastery among elementary and middle school students at risk in mathematics

In the present study, we evaluated the number of attempts required to master specific subskills for working with whole and rational numbers among students at risk for math difficulties. Participants included a subset of students in grades four through eight receiving supplemental math support. Mastery—defined as 85% correct on short tests—was assessed following instruction for each subskill. Using survival analysis, we evaluated the number of attempts required to reach a .50 and a .90 probability of mastery on each subskill. The number of required attempts varied across subskills, with many subskills requiring more than one attempt to demonstrate mastery. Further, some of the most difficult content was aligned with curricular standards below students’ grade level. Thus, among students identified for supplemental support, it may be worthwhile to remediate select subskills that fall outside of the grade‐level curriculum before providing additional instruction on grade‐level content. Implications for math subskill assessment and remediation are discussed along with limitations and directions for future research.     

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.