Representation of time in time-place learning

Ordinal, interval, and circadian mechanisms of solving a time-place task were tested. Rats searched for food twice in the morning and once in the afternoon (Group AB-C,n=5) or once in the morning and twice in the afternoon (Group A-BC,n=5) in a box with four food troughs. The location of the food depended on the time of day in a 12:12-h light:dark cycle. Acquisition was documented by foodsite inspections at the correct locations prior to food availability. On nonrewarded probes, the time of the middle search (B) was shifted late (for Group AB-C) or early (for Group A-BC). The rats visited Location B at chance, contrary to an ordinal mechanism. When the posttesting meal and light-dark transitions were omitted, the rats visited correct locations with impaired performance but at abovechance levels on nonrewarded probes. The results are consistent with interval and circadian representations of time.     

Aversively motivated changes in meal patterns of rats in a closed economy: The effects of shock density

Rats lived continuously in an operant chamber in which they were able to press a bar to obtain food on a chained FR50:CRF schedule that allowed them control of both the size and frequency of individual meals. Independent groups of animals were scheduled to receive 12, 24, 48, or 96 electric shocks per day, which were given randomly in time and independent of the subjects’ behavior. Rats could avoid shock by remaining in a safe area of the chamber, but they were always at risk while barpressing. The introduction of shock resulted in a number of changes in feeding patterns. In rats exposed to a possible 12 shocks/day, meal size increased whereas meal frequency changed very little. At 24 shocks/day, meal frequency decreased whereas meal size increased such that net intake remained stable relative to a preshock baseline period. As shock density was increased to 48 or 96 shocks/day, total intake was suppressed. At 96 shocks/day, both meal frequency and meal size decreased dramatically. Shock-related changes were also observed in rates of operant responding and in the amount of time the animals engaged in feeding-related behavior. All of the animals were able to achieve a greater than 50% reduction in the total number of shocks received relative to equivalent random samples of their position in the apparatus taken during baseline. These results support the position that the nature of defensive changes in feeding behavior that are seen when an aversive stimulus is introduced: into a simulated foraging situation varies as a function of risk.     

Autonomy at mealtime: Building healthy food preferences and eating behaviors in young children

This article discusses family-style meal service as a means to building autonomy and healthy eating behaviors in young children. The authors discuss the development of food preferences, age-related developmental responses to food, and the importance of socially mediated exposure to food as a way to increased food acceptance. Guidelines for implementing family-style mealtimes in child care settings are outlined. To think, “On a typical day in 1992, 1.9 million children ate at least one of their meals in a child care center or family day care home”. (Briley, Roberts-Gray, & Simpson, 1994).     

Rats' performance on an interval time-place task: Increasing sequence complexity

Rats were trained on an interval time-place learning (TPL) task in which the location of food availability depended on the time since the start of the session. Each of four levers (numbered 1, 2, 3, 4) provided food on an intermittent schedule for two nonconsecutive 3-min periods. The order in which the levers provided food was 1, 2, 4, 3, 2, 3, 1, 4. This order was consistent across sessions. Previous research conducted in our lab has shown that when only four “places” are used, rather than the eight in the present study, rats use a timing strategy to track the location of food. Pizzo and Crystal (2004) recently trained rats on an interval TPL in which each of eight arms of a radial arm maze provided food. They found evidence suggesting that rats used both spatial and temporal information. In the present study, in which a revisiting strategy was used (i.e., each lever provided food on more than one occasion), the rats tracked both the spatial and the temporal availability of food for the first half of the session. Interestingly, in the second half of the sessions, the rats appeared to be timing the availability of food even though they did not know where it would occur. That is, the rats knew the temporal, but not the spatial, contingencies for the second half of the session. It appears that the requirement of revisiting a previously reinforced lever resulted in rats' no longer being able to solve the spatial aspect of the task.     

Adjunctive behavior of the rat under periodic food delivery in a 24-hour environment

The behavior of 4 rats living in complex environments was monitored 24 h per day during free-feeding baseline and under conditions of periodic access to food. Under the periodic schedules, the minimum interfood interval (IFI) was increased from 16 to 512 sec in an ascending series. Periodic food produced robust overall increases in investigation of the feeder, drinking, general activity, and rearing, but not in wheel-running. The temporal distribution of behavior within the IFI was similar across subjects and supported the hypothesis that some responses were largely time-locked to the period immediately following eating, while other responses expanded to fill the interval. However, these response differences were not adequately captured by present classification schemes. Finally, the distribution of drinking following a food pellet strongly resembled the distribution of drinking following bouts of feeding in baseline. The results suggest that adjunctive behavior stems from three sources: (1) a simple increase in the number of opportunities for expression of normal preprandial and postprandial behavior, (2) an increase in the preprandial behavior directed toward the site of expected food, and (3) an increase in the postprandial distribution of both site-directed and more general exploratory behavior. These findings suggest that adjunctive behavior is not extraneous, but is an orderly distribution of responses ordinarily related to feeding and foraging for food.     

襄樊职业技术学院学生膳食营养状况

目的 了解襄樊职业技术学院学生营养状况并针对问题提出改进措施，以便为高职学生提供合理的膳食营养。方法 采用24h膳食记录法和称重法。连续调查5d学生膳食状况，计算每人每日能量和营养素摄入量，与推荐摄入量进行比较。结果 男生能量摄入量占推荐摄入量的93．9％。女生为77．9％;蛋白质摄入量占推荐摄入量男生为89．5％，女生为86．9％；钙摄入量不足，男生为推荐摄入量的67．4％，女生为57.3％；视黄素、维生素B2、维生素C和锌、铁也存在不同程度的摄入不足。结论 应对学生进行营养教育，提高早餐质量和比例，增加副食摄入，补充牛奶。     

草原文化背景下蒙餐文化特征解析

草原文化是内蒙古独特的资源优势。以草原文化为依托的蒙餐文化,具有绿色天然、饮食一体、注重本味、突出礼仪、食娱同行、体现民俗、营养保健、医食同补的特征,迎合了时代消费理念。新经济时代,应大力弘扬蒙餐饮食文化,增强蒙餐的影响力,为当地经济发展助力。     

Procedure for preventing response strain on random interval schedules with a linear feedback loop

An experiment examined the impact of a procedure designed to prevent response or extinction strain occurring on random interval schedules with a linear feedback loop (i.e., an RI+ schedule). Rats lever-pressed for food reinforcement on either a RI+ or a random interval (RI) schedule that was matched to the RI+ schedule in terms of reinforcement rate. Two groups of rats responded on an RI+ and two on an RI schedule matched for rate of reinforcement. One group on each schedule also received response-independent food if there had been no response for 60 s, and response-independent food continued to be delivered on an RT-60 schedule until a response was made. Rats on the RI and RI+ obtained similar rates of reinforcement and had similar reinforced inter-response times to one another. On the schedules without response-independent food, rats had similar rates of response to one another. However, while the delivery of response-independent food reduced rates of response on an RI schedule, they enhanced response rates on an RI+ schedule. These results suggest that rats can display sensitivity to the molar aspects of the free-operant contingency, when procedures are implemented to reduce the impact of factors such as extinction-strain.     

Sign-tracking (autoshaping) in rats: A comparison of cocaine and food as unconditioned stimuli

A series of experiments was performed to determine whether sign-tracking would occur in rats with intravenous (i.v.) cocaine as the unconditioned stimulus. In Experiment 1, a retractable lever paired with food produced strong sign-tracking, but a lever paired with one of three doses of i.v. cocaine did not elicit any approach or contact behavior. Experiment 2 demonstrated that doses of cocaine that did not elicit sign-tracking would function as a positive reinforcer for a lever contact operant. In Experiment 3, an artificialconsummatory response was added to make the cocaine reinforcement episode more behaviorally comparable to that occasioned by food. Although the rats readily performed this response when it was required to receive cocaine infusions, they still did not contact a lever that signaled the availability of these infusions. It appears that cocaine is different from other positive reinforcers (e.g., food, water, warmth, or intracranial stimulation) in that it will not produce sign-tracking in rats.     

Variation in the effectiveness of instructional interactions across preschool classroom settings and learning activities

This exploratory study examined the extent to which the effectiveness of instructional interactions varies among classroom social settings (i.e., large group, free choice, meals, and routines), learning activities (i.e., shared reading, literacy, math, science, social studies, and esthetics), or their combination. Participants were 314 preschool teachers primarily serving children from low-income backgrounds. Instructional interactions were measured in multiple cycles across one day of classroom observation as teachers engaged in a variety of settings and learning activities. Linear mixed models indicated that the effectiveness of teachers’ instructional interactions was generally higher in the large group setting than in free choice, meals, and routine settings. When considering settings and learning activities in combination, teachers displayed the most effective global instructional interactions when leading science activities in large group or free choice settings, and the most effective literacy-focused interactions during large group literacy activities.     

The lag effect in secondary school classrooms: Enhancing students’ memory for vocabulary

Educators often face serious time constraints that impede multiple repetition lessons on the same material. Thus, it would be useful to know when to schedule a single repetition unit to maximize memory performance. Laboratory studies revealed that the length of the retention interval (i.e., the time between the last learning session and the final memory test) dictates the optimal lag between two learning sessions. The present study tests the generalizability of this finding to vocabulary learning in secondary school. Sixth-graders were retaught English–German vocabulary after lags of 0, 1, or 10 days and tested 7 or 35 days later. In line with our predictions, we found that the optimal lag depends on the retention interval: Given a 7-day retention interval, students performed best when relearning occurred after 1 day. When vocabulary was tested after 35 days, however, students benefited from lags of both 1 and 10 days. Model-based analyses show that enhanced encoding processes and stronger resistance to forgetting—but not better retrieval processes—underlie the benefits of optimal lag. Our findings have practical implications for classroom instruction and suggest that review units should be planned carefully by taking the time of the final test into consideration.     

Foraging for covered and uncovered food on a radial maze

Rats were trained to forage for food on a four-arm radial maze. Each arm of the maze was defined as a patch and contained four feeding stations. Each patch contained a total of 20 45-mg food pellets, with the first feeding station in each patch baited with 1 pellet and the remaining stations baited with 1, 5, or 13 pellets. In Experiment 1, one group of rats was tested with feeders open and food readily accessible, and another group was tested with metal covers on the feeders, which necessitated extra time to gain access to food. With open feeders, the rats visited each feeder in a patch in the order in which they encountered the feeders, from the center of the maze to the end of the arm. The rats in the group with the covered feeders often visited the feeders containing 5 or 13 pellets first and the feeders containing 1 pellet last. In Experiment 2, it was found that the rats switched readily between these two foraging strategies when tested with covered and open feeders on alternate sessions. The extra time and effort required to uncover food appeared to produce selective foraging in rats.     

Quality in Kindergarten Classrooms: Observational Evidence for the Need to Increase Children's Learning Opportunities in Early Education Classrooms

Research Findings: Using observational data gathered in 730 kindergarten classrooms in 6 states, the present study focuses on the quality of children's learning opportunities in kindergarten classrooms. Findings show that overall, children experience moderate to low levels of quality in the areas of classroom organization and instructional support in kindergarten. Results are also presented in comparison to children's experiences in the pre-kindergarten year. These comparisons indicate that kindergarten children spend a greater proportion of the school day in language arts, math, and whole-group instruction and less time in centers than they do in pre-kindergarten. An examination of predictors of kindergarten classroom quality indicated that program characteristics (i.e., adult–child ratio, length of school day) and teacher psychological variables (i.e., beliefs and depressive symptoms) were stronger predictors of classroom quality than were teacher experience and educational background. Practice or Policy: Findings are discussed in terms of implications for children's academic and social development in kindergarten as well as for kindergarten teacher preparation and development.     

Discrimination of what, when, and where is not based on time of day

Rats (n=6) visited four baited locations (randomly chosen on each trial; study phase), one of which was randomly selected to provide chocolate. After short (1-h) or long (25-h) retention intervals (RIs), eight locations were available, and the four locations not available in the study phase provided food (test phase); the chocolate location also provided food after long RIs. More visits to the chocolate location occurred after long RIs than after short RIs. Next, chocolate was paired with LiCl during the long RI (i.e., after encoding the chocolate location). Fewer revisits to the chocolate location occurred after LiCl than in previous testing with the long RI. The rats demonstrated complete transfer when grape replaced chocolate after LiCl-chocolate pairing. The discrimination of what, when, and where could not be based on adopting different revisit strategies at different times of testing.     

Evidence for a calorically costly negative consummatory contrast effect in rats

For 2 h prior to their daily meal of Purina Chow, rats (which were 14% below ad-lib weight levels) had access to a sucrose solution. For half (Group 16-4), the solution was alternated daily between 18% and 4%; for the other half (Group 4-4), the solution was always 4%. On 18% days, Group 16-4 consumed significantly more calories and gained significantly more weight than did Group 4-4, because of a greater consumption of sucrose calories (Purina intake was similar for the two groups). On 4% days, however, Group 16-4 consumed both significantly fewer sucrose calories and significantly fewer Purina calories than did Group 4-4. These two contrast effects resulted in a 17% shortfall in total caloric intake for Group 16-4 on 4% days. As a consequence, Group 16-4 showed a significant drop in body weight, compared to Group 4-4, on 4% days. A second experiment was carried out to investigate whether the contrast-induced reduction in Purina intake shown by Group 16-4 on 4% days would be eliminated if (1) a 30-min interval separated sucrose ingestion from Purina ingestion, or (2) a 25-min interval plus 5-mmn exposure to 16% sucrose separated ingestion of 4% sucrose from Purina ingestion. Purina intake was still suppressed in Group 16-4 under both conditions.     

Eco-friendly alternative refrigeration systems

Refrigeration applications at the domestic, commercial and industrial levels are becoming an integral part of the present day living. The demand and supply of refrigeration systems is increasing day by day with the changing lifestyle. The existing compressor-based refrigeration (i.e., mechanical refrigeration) system has reached the maximum level of innovation. For the last few decades, there has not been any significant increase in the efficiency (i.e., coefficient of performance, COP) of the system. Moreover, with the increasing awareness of environmental degradation, the production, use and disposal of ChloroFluoro Carbons (CFCs) and HydroChloroFluoroCarbons (HCFCs) as refrigerants in mechanical refrigeration system has become a subject of great concern. However, such systems are being developed using more ecofriendly refrigerants viz., air, CO₂, NH₃, etc. Besides, efforts are being directed to develop other types of refrigeration technologies e.g., magnetic refrigeration, thermoelectric refrigeration (discussed in Part 1) and thermoacoustic refrigeration (discussed in Part 2), which will be moreecofriendly, cost effective, efficient, simple in design, convenient and reliable.     

The effect of discrimination training on the response rate and response duration of the rat

Response rate (responses per minute) and response duration (time in seconds per press) were recorded in rats shifted from multiple variable-interval variable-interval (mult VI VI) to multiple extinction variable-interval (mult EXT VI). This procedure produced positive contrast (i.e., a decrease in response rate in EXT and an increase in VI) in 11 of 12 rats and, in addition, produced an increase in response duration (i.e., bar holding), which, for the most part, was confined to the EXT component of the mult EXT VI condition. One of the 12 rats showed negative induction (i.e., a decrease in response rate in both the EXT and VI components), and also an increase in response duration in both the EXT and VI components of the mult EXT VI condition. The results indicate that generalization of behavior from the EXT to the VI component can produce negative induction, and that such generalization must be prevented if positive contrast is to occur in the rat.     

Resistance to extinction of a learned taste aversion varies with time of conditioning

Sixteen rats were maintained out of doors in cages with natural light, temperature, and social stimulation for 3 months. Subsequently, by pairing the taste of sucrose with IP injections of LiCl, the rats were conditioned to avoid sucrose. Each of four groups of rats received the CS-US pairing at a different time of day. Times of conditioning were 6 a.m., 12 a.m., 6 p.m. and 12 p.m. EST. A two-bottle preference test between 4% sucrose solution and tap water was initiated 24-h after conditioning. Daily measurements of preference were continued for 16 consecutive days. Results indicated that, although all groups initially exhibited equivalent sucrose aversions, the groups conditioned at 12 a.m. and 6 p.m. extinguished within 12 days while the 6 a.m. and 12 p.m. groups continued to manifest profound aversions for sucrose throughout the 16 test days.     

Reinforcing the occurrence or nonoccurrence of interim drinking

Four pairs of rats were studied in a yoked control design intended to determine if an interim activity (schedule-induced drinking) was sensitive to operant contingencies. Food was always presented on a fixed-time 30-sec schedule. Additionally, a positive or negative operant contingency was in effect during the first 6 sec of each interval. The positive (drink/food) contingency produced an extra food presentation at the 6th second of an interval if the lead rat drank at least once in the first 6 sec. The negative (no-drink/food) contingency produced an extra food presentation only if the lead rat did not drink in the first 6 sec. Two pairs of rats were first exposed to the positive contingency and then to the negative contingency. Two pairs received training in the reverse order. In drink/food training, all lead rats developed patterns of drinking that produced extra food presentations in most intervals. There were some indications that the positive contingency facilitated early acquisition of drinking, but the yoked rats eventually developed temporal distributions and asymptotic levels of drinking comparable to those that occurred in lead rats. In no-drink/food training, the two lead rats initially exposed to the positive contingency showed high levels of drinking inappropriate to the negative contingency, but the two lead rats initially exposed to the negative contingency showed appropriately low levels of drinking. The latter effects seem attributable to the no-drink/food contingency.     

The influence of temporal spacing on time-place discrimination

The conditions under which circadian and interval-timing mechanisms are used in time-place discrimination were investigated. Rats earned the first daily meal by pressing a lever beginning 3.5 h after the start of the session and a second daily meal by pressing another lever. The second meal started 3.5 or 7 h (Experiment 1) or 0.75 or 1.75 h (Experiment 2) after the start of the first meal, using independent groups. In Experiment 1, approximately half of the rats used an interval-timing mechanism, and the other half used a circadian mechanism. In Experiment 2, the rats timed two intervals, one from the start of the session until the first meal and the other from the first to the second meal. A circadian mechanism is relevant to timing intervals in the range of 1.75–3.5 h, and an interval-timing mechanism can be used to time intervals from 0.75–7 h.