Latent learning in a swimming pool place task by rats: Evidence for the use of associative and not cognitive mapping processes

Using a latent learning paradigm, the experiments examine two hypotheses of how rats solve place navigation tasks. According to associative theory, experience with all relevant cues is required for accurate navigation. According to cognitive mapping theory, animals can generate novel trajectories from knowledge of spatial relations of objects in the environment. Rats that had been placed on a platform, which was submerged in a pool of opaque water and was moved each day, were tested later for their ability to find the platform using only surrounding room cues. One 30-sec exposure to a platform location was effective in improving performance. Improvement was greatest when tests were given within minutes of placement, but facilitation was obtained for as long as 4 hr. Improved performance was obtained as soon as rats acquired the procedural aspects of the task but did not increase with subsequent practice. Improved performance was also obtained when pre-trained rats were tested in a novel environment. Despite the advantage conferred by exposure to the target platform, test swims were not accurate, placement-induced improvement was not as great as that following a single swimming trial, and placement combined with a swim resulted in best performance. The results suggest that rats use associative learning processes rather than cognitive mapping to solve place problems in a swimming pool.     

Rats (Rattus norvegicus) modulate eating speed and vigilance to optimize food consumption: effects of cover, circadian rhythm, food deprivation, and individual differences.

The eating behavior of rats (Rattus norvegicus) given food pellets of specified size was examined as a function of environmental, circadian, and experiential influences. Eating times were shorter in lighted, exposed environments than in dark, covered environments, even though in novel, exposed conditions the rats made many scanning movements as they ate. Eating time also varied as a function of the circadian cycle in that eating times were shorter in the night portion of the day-night cycle. Finally, eating times decreased if rats were food deprived, and deprivation had a small but enduring influence. Within the tests there were differences in the eating times of individual rats that were not attributable to the experimental manipulations. That rats can optimize food intake by varying eating speed is discussed in relation to physiological regulation of feeding and to optimal foraging theory.     

Assessing School Academic Productivity: The Case of Chicago School Reform

This paper considers the issues raised in using standardized achievement test scores for purposes of examining the academic productivity of schools. We critique some commonly used practices by urban school districts and suggest an alternative approach – the school productivity profile. This profile is based on an assessment of each school's contribution to student learning, or value-added, rather than just the overall level of student attainment. We illustrate, using 10-year achievement trend data from the Chicago Public Schools (CPS), both the problems with some commonly reported indicators of school effectiveness and the idea of a school productivity profile. While our analyses suggest broad-based improvements in student learning in many Chicago schools over the past 10 years, we also found that the current testing system is not well designed to make such judgments accurately. We conclude that extant standardized testing systems, like the ITBS used in Chicago, do not afford an accurate basis for assessing school productivity and how this might be changing over time. These results have important policy implications. As school districts seek to become more outcome oriented, they will need to invest in better testing and reporting systems in order to know whether they are making genuine progress in this regard.     

Choice, experience, and the generalized matching law

Five pigeons were exposed to different pairs of concurrent variable-interval, variable-interval schedules on nine experimental conditions of 30 sessions each. For every session, the parameters of the generalized matching equation were computed for the first five, six, seven, eight, and nine experimental conditions. The exponent a, both for response and time distribution, tended to decrease with increases in number of experimental conditions and to increase with number of sessions per condition, but values of k (bias) varied unsystematically. When the subjects were exposed to five new pairs of schedules, with 55 sessions per condition, the findings were confirmed. Data from the literature on the generalized matching law suggest that the variability of exponent values may be explained in part by the use of naive or experienced subjects in different investigations and by the variability in number of experimental conditions and in number of sessions per condition.     

Auditory enhancement and the perception of concurrent vowels

Listeners identified both constituents of double vowels created by summing the waveforms of pairs of synthetic vowels with the same duration and fundamental frequency. Accuracy of identification was significantly above chance. Effects of introducing such double vowels by visual or acoustical precursor stimuli were examined. Precursors specified the identity of one of the two constituent vowels. Performance was scored as the accuracy with which the other vowel was identified. Visual precursors were standard English spellings of one member of the vowel pair; acoustical precursors were 1-sec segments of one member of the vowel pair. Neither visual precursors nor contralateral acoustical precursors improved performance over the condition with no precursor. Thus, knowledge of the identity of one of the constituents of a double vowel does not help listeners to identify the other constituent. A significant improvement in performance did occur with ipsilateral acoustical precursors, consistent with earlier demonstrations that frequency components which undergo changes in spectral amplitude achieve enhanced auditory prominence relative to unchanging components. This outcome demonstrates the joint but independent operation of auditory and perceptual processes underlying the ability of listeners to understand speech despite adversely peaked frequency responses in communication channels.