Child Care for Children in Poverty: Opportunity or Inequity?

Data from a nationally representative survey of child care centers and a 5-site, observational study of centers were used to examine the quality of care provided to children from low-income families. Comparisons were made to a national sample of centers; among Head Start, public school-sponsored, and other community-based subsidized centers; and among centers that served families from differing socioeconomic groups. The quality of care in centers that served predominantly low-income children was adequate, but highly variable, with structural indices exhibiting higher quality than observations of global quality and of staff-child interactions. When compared to Head Start and public school-sponsored centers, the community-based centers had smaller groups and fewer children per teacher for preschoolers, but also had less well educated and compensated staff. Centers that predominantly served children from upper-income families provided the highest quality of care across multiple indices, and those that predominantly served children from middle-income families almost uniformly provided the poorest quality of care. The centers that served children from low-income families did not differ significantly in quality from the upper-income centers on most indices. However, the teachers in these programs were observed to be less sensitive and more harsh than teachers in the centers that served more advantaged families. The implications of the findings for research and policy are discussed.     

Sources of Inequity: understanding students' responses to assessment

This article considers some of the implications for assessment practice of current views about the nature of learning, and achievement. Evidence from national surveys is presented that demonstrates some of the different ways, ‘tasks' and responses to them are understood by assessors and students. This is followed by a review of evidence about differential sub‐group performance which is then examined to identify potential sources of inequity in assessment practice.     

Inequity as a Source of the Cultural Gap in an Urban School-University Collaborative

Based on a 5-year naturalistic evaluation of an urban university-school collaborative that focused on preparing teachers for urban schools, this analysis was initiated to determine to what extent inequalities between the university and school personnel mitigated the attainment of intended outcomes. Results indicated that some positive change occurred, such as professors and teachers learning to speak the same language on instructional teams, which led to improved field experiences for students. However, cultural differences with concomitant inequities between school and university personnel prevented more permanent change. Inequities of power were inadvertently written into the proposal and were exacerbated at two levels: (1) the collaborative policy board, in which districts, due to larger representation, wielded greater power over budget and hiring in the collaborative; and (2) instructional teams where professors wielded power over several teachers with resistance from teachers. By the end of 5 years, the funded portion of the urban teacher education program that included a collaborative policy board and instructional teams had fallen mostly by the wayside. Cooperation between professors and teachers reverted to precollaborative levels with only loose coupling remaining. Preservice students continue to do field experiences in the professional development schools under supervision. The university education unit recognized the benefits, but continues to struggle with how to revive the level of cooperation that began with the urban program and to create long term partnerships that go beyond mere placement of students into the field.     

Higher order conditioning of a taste aversion

Two groups of rats each received 5 drops of NaCl solution from a dropper placed directly inside the mouth. The experimental group was then injected with lithium chloride to establish a conditioned taste aversion. The control group was injected 24 h later. After a recovery day the above procedures were repeated. On the next day both groups received 5 drops of a saccharin solution followed immediately by 5 drops of the NaCl solution. Subsequent preference tests established that the experimental group had learned an aversion to the saccharin solution as a result of its pairing with the NaCl solution which had previously been associated with poisoning. These results demonstrate that higher order conditioning of a taste aversion can be established using tastes as both the first-order stimulus and the second-order stimulus.     

Slow reacquisition of a conditioned taste aversion

Rats were used to examine the extent to which extinction of an acquired conditioned taste aversion retards subsequent reacquisition. A saccharin-flavored solution (sac) was paired with LiCl and then followed by CS-alone extinction trials with this flavor. A control group received a different flavor, decaffeinated-coffee (coff), during initial conditioning and extinction. Sac was then paired with LiCl for all rats during a second conditioning phase. Reacquisition of the aversion to sac was retarded relative to the acquisition of an aversion to sac by the control group. A similar experiment with fewer extinction trials, but still with complete loss of the initial aversion, did not obtain slow reacquisition. The results are discussed with respect to an interference view of extinction and the slow-reacquisition effect.     

Injected flavor as a CS in the conditioned aversion preparation

Three experiments were conducted to determine the effectiveness of intravenous (IV) flavor injections in the formation of conditioned taste aversions and in the attenuation of neophobia. In Experiment 1, two groups of rats were permitted to drink either a .1% saccharin solution or tap water followed immediately by IV injections of lithium chloride (LiCl), and two more groups were given IV injections of a 2% saccharin solution followed immediately by IV injections of either LiCl or distilled water. Injected flavor did not serve as an effective CS for the conditioning of an aversion to .1% saccharin. The second experiment employed a two-bottle procedure to detect attenuation of neophobia using the injected-flavor technique. It was found that, whether saccharin had been injected intravenously (2%), injected intraperitoneally (2% IP), or orally consumed (.1%), neophobia for .5% saccharin was attenuated equally relative to controls. CS-US intervals were manipulated in the final experiment such that IP injections of 2% saccharin solution were followed 0–480 min later by IP injections of LiCl. In this case, it was shown that injected flavor (2% saccharin) could act as an effective CS if the US was delayed (optimally about 120 min) and when the test solution was .1% saccharin. The delay gradient found in Experiment 3 was interpreted as a generalization gradient where optimum conditioning was displayed at the point where the concentration of saccharin circulating in the animal at the time of illness onset most closely matched the concentration of the test solution.     

Sexually dimorphic extinction of a conditioned taste aversion in rats

The existence of a sexual dimorphism in the extinction of conditioned taste aversions in both fluid-deprived and nondeprived rats was investigated. When nondeprived rats were poisoned with LiCl after consuming a sucrose solution, males extinguished the subsequent conditioned taste aversion more slowly than females. There was no difference in the rate of extinction of a LiCl-induced conditioned taste aversion in fluid-deprived rats. Using marihuana extract distillate as the toxin, it was shown that the dimorphism found in the nondeprived rats is not a toxin-specific effect, and does not appear to be due to the males being made more ill. Possible explanations for the appearance of the dimorphism and its relation to the deprivational state of the organism are discussed.     

Food aversion learning in kangaroo rats: A specialist-generalist comparison

Two species of kangaroo rat (Dipodomys), varying in their degree of dietary specialization, were compared in a series of food aversion learning experiments to test the hypothesis that rapid aversion learning is an adaptation of relatively generalist feeders. The more generalist species indeed learned better or more rapidly in certain experiments, but species differences were at least partly a function of the specific test foods. Interpretation of results is complicated by differences between the two species in their initial reactions to particular foods, in the relative efficacy of different foods in supporting learned aversions, and perhaps even in their physiological responses to illness-inducing and control procedures.     

Taste quality and extinction of a conditioned taste aversion in rats

Rats (Rattus norvegicus) that received a taste cue (saccharin, saline, quinine, or sucrose) paired with a lithium chloride (LiCl) injection displayed a robust decrease in consumption of that taste, relative to controls that had the taste unpaired with LiCl. Consumption of the paired taste increased with each nonreinforced presentation (i.e., extinction). After asymptotic extinction, rats that had had a 0.1% saccharin cue paired with LiCl consumed less of the saccharin solution than did controls. A similar data pattern was observed with a 10% sucrose solution. These results are consistent with the view that some aspect of the excitatory CS-US association remains after extinction. On the other hand, rats that had a bitter (0.005% or 0.001% quinine) or salty (1% or 0.5% saline) solution paired with LiCl drank similar amounts of the fluid as controls after asymptotic extinction treatment. Together, these experiments suggest that a taste that is either sweet or preferred is required in order to demonstrate the chronic decrease in fluid consumption after extinction treatment. The data suggest that the conditioning experience prevents the later development of a preference for the sweet taste, rather than there being a retained aversion that suppresses fluid consumption.     

我国义务教育校际资源分配不公平现象的现状、原因及对策

本文通过比较优质学校与普通学校在教育经费收入、教育经费支出、办学条件等方面存在的差异,分析校际资源配置不公平的状况及其形成的原因,并结合教育资源公平分配的五大原则,提出了消除不公平现象的建议,以为推进义务教育公平政策的制订提供参考.     

Spontaneous recovery after extinction of a conditioned taste aversion

Four experiments examined whether or not spontaneous recovery could occur after extinction in the conditioned taste-aversion paradigm. After three extinction trials, spontaneous recovery was obtained over an 18-day retention interval (Experiments 1, 2, and 3). The effect was not due to changes in the unconditioned preference for saccharin over the retention interval (Experiment 2) or to an increase in a nonextinguished aversion over time, as indicated by tests with both the original, nonextinguished aversion (Experiment 1) and with a weaker one (Experiment 3). Spontaneous recovery was not obtained when extinction was overtrained (eight trials) and a 49-day retention interval was used (Experiment 4). However, saccharin intake at asymptote reached the level of baseline water intake, and not the highly preferred level shown by never-conditioned controls. Results of all four experiments suggest that extinction does not return an averted taste to the status of an unconditioned one.     

Increase in retention of a taste aversion by weanling rats after a long interval

Weanling rats were tested for retention of an aversion to a novel flavor (chocolate milk) that had been conditioned as a single-element conditioned stimulus (CS) or in compound with a novel ambient odor (banana). The presence of the ambient odor during conditioning had no effect on flavor aversion shortly thereafter, confirming previous results. The flavor aversion observed 21 days after conditioning, however, was significantly stronger for pups conditioned with the single-element CS than for those given the flavor-odor compound as the CS. This retention effect was due to a surprisingincrease in the conditioned aversion observed 21 days after conditioning with the single-element CS. A second experiment confirmed this paradoxical increase in retention of the aversion to chocolate milk. This experiment also verified that no such increase occurred in retention of the conditioned aversion to a different flavor (saccharin), whether the initial aversion was strong or weak. The results may be explained in terms of generalized latent inhibition from consumption of mother’s milk.     

Extinction of a taste aversion in the absence of the consummatory response

Rats were initially conditioned to avoid saccharin presented orally and were then given 40 intravenous injections of saccharin or saline. Those injected with saccharin showed more rapid extinction of the aversion to saccharin presented orally. Results are related to studies of shock avoidance using curarized subjects.     

Timing of interfering events in one-trial serial overshadowing of a taste aversion

This set of experiments examined the question of when a stimulus would be most effective in overshadowing the acquisition of long-delay taste aversion learning. In Experiment 1 rats drank sucrose, the target solution, followed by a hydrochloric acid (HCl) solution before lithium injection some time later; HCl was presented either early or late in the interval. The late condition produced greater overshadowing than the early condition. The importance of the HCl-injection interval was confirmed by Experiment 2, in which the sucrose-injection interval was varied. Experiment 3 found that even placement in a different context – an event that normally produces little overshadowing of a CTA – produced one-trial overshadowing of a sucrose aversion as long as the context was novel and exposure to it occurred immediately before lithium injection. No current theoretical account of one-trial overshadowing predicts that a late event produces more overshadowing than an early event. This result can, however, be accommodated within a modified version of the Rescorla-Wagner model.     

Long-term retention of a conditioned taste aversion in preweanling and adult rats

The retention and extinction of a conditioned taste aversion after either short (6-day) or long (60-day) intervals was investigated in preweanling (18-day-old) and adult rats. Taste-only and illness-only control conditions were employed, as were variations in the concentration of the US (holding LiCl amount constant). Results indicated that after the short retention interval, retention of the taste aversion was equivalent for both ages. After the long interval, however, the 18-day-old rats exhibited significantly weaker taste aversion than their adult counterparts— infantile amnesia. Manipulation of US concentration had no effect on the magnitude of the taste aversions for either age or retention interval. The results are discussed in terms of their implications for infantile amnesia and general laws of learning.