Preshock Period Research Articles

Analysing the differential impact of the COVID-19 pandemic on the resilience of the tourism economy: A case study of the Chengdu-Chongqing urban agglomeration in China

The outbreak of the COVID-19 pandemic in 2019 had a profound impact on the tourism economy, underscoring the critical importance of assessing and analyzing tourism economic resilience. Traditionally, prior research predominantly focused on constructing evaluation systems based on three dimensions: Risk preparedness capability, Restoration capability, and Reorganization and modernization capacity. In this study, we take an innovative approach by incorporating urban network thinking and establishing a tourism economic network, while introducing the dimension of “The rationality of network structure.” To comprehensively understand the dynamics of tourism economic resilience, we divided the period from 2018 to 2021 into three distinct phases: Stable period, Pre-shock period, and Shock period. This division allowed us to conduct comparative research that highlights the variations in tourism economic resilience across these different time frames. Additionally, we employed advanced methods, such as kernel density estimation and the GTWR model, for empirical analysis of tourism economic resilience within the Chengdu-Chongqing city cluster. The results of our research unveiled that Chengdu and Chongqing both demonstrate a remarkable level of resilience within their tourism economies. However, given their status as the “dual core” of the Chengdu-Chongqing city agglomeration, they are inherently more susceptible to significant fluctuations when confronted with shocks. The spatial pattern of tourism economic resilience is characterized by prominent wings on both sides, a North-South balance, and a central region with vulnerabilities. The predominant evolutionary patterns are marked by multi-level stabilization, moderate growth, and moderate decline. Ziyang is an exceptional region within the broader growth zone, and its reduced risk preparedness capability has led to an overall decline in tourism economic resilience. Furthermore, key influencing factors, including the economy, infrastructure, and ecological environment, exhibit significant spatial heterogeneity. In conclusion, our study offers valuable insights into researching tourism economic resilience under external shocks, such as the COVID-19 pandemic. These findings can be instrumental in guiding policymakers as they develop effective strategies to bolster tourism economic resilience.

Financial Contagion of the Commodity Markets from the Stock Market during Pandemic and New Sanctions Shocks

In the context of financial globalization, there is an increasing transmission of global turbulence between different markets, which enhances overall financial instability. The purpose of this study is to identify the financial contagion of the commodity market from the stock market in the 1920s. The research hypothesis is that contagion manifested itself during the period of pandemic shocks of 2020-2021 and new sanctions shocks of 2022-2023. Based on 2016-2023 data on the intersessional average daily return of the S&P GLOBAL 100 index and 22 commodity futures, DCC GARCH models are built. Significant increases in these correlations during periods of external shocks indicate potential contagion. A dynamic Student's t-test for the equality of correlations in the pre-shock period and in the sliding window within the shock and inter-shock periods is used to definitively prove the presence or absence of contagion. The study confirmed the contagion of 22 commodity markets from the stock market of varying strength and duration, both during the pandemic and new sanctions shocks. It proved that the metals market, especially the gold market, was the most susceptible to contagion during the period under review. Copper and zinc turned out to be risk dampers during the period of new sanctions. Among food products, the sugar market has demonstrated the greatest propensity to contagion, but during a period of relative stability it has proven its ability to mitigate systemic risks. A number of agricultural commodities (e.g., soybeans and soybean products, corn, wheat), as well as Brent oil, have shown relative resistance to contagion and are recommended as hedging tools. The results and conclusions of the study can be useful to investors in managing optimal portfolios, and to the state when adjusting anti-crisis financial policy during the period of external shocks affecting the economy.

The Resilience of Russia's Regions in the Conditions of Recovery Growth: Bouncing Forward or Bouncing Back?

The recovery growth of regional economies after shocks can be expressed both in a return to the initial state and in a new development trajectory. Many researchers associate the direction of the movement caused by the shock with sectoral transformations, considering structural proportions in the economy as the main factor in regional resilience. This study aims to analyze the recovery growth trajectory of Russian regions in the post-pandemic period, as well as to find out whether shifts in the sectoral structure of their economies have affected it. The hypothesis of the study was the assumption that the vector of regional development is determined by the changes in the sectoral structure of the region that occurred during the crisis. Research methods included: analysis of the deviations of the actual values of GRP and employment indicators from their possible values, defined as a continuation of the trend of economic development in the pre-shock period; comparison of changes in the indicators of the economic development of regions with changes in the growth rates of individual sectors of the economy: industry, agriculture, construction, transport, trade and services. The results of the study showed significant differences in the speed and nature of recovery processes in Russia's regions. The vast majority of regions returned to the pre-shock trajectory of development. At the same time, some regions could not cope with the shocks of the corona crisis and saw their socio-economic situation worsen, while some showed a “leap forward” with higher development indicators. The author comes to the following conclusions: 1) sectoral transformations of the regional economy during the crisis are not decisive in determining the trajectory of the recovery movement and a “favorable” change in the sectoral structure can be neutralized by the influence of other factors; 2) the high vulnerability of the region's economy and its individual industries to shock events does not mean a longer period of recovery growth. From a practical point of view, this is important for understanding what aspects of sustainability may be relevant for the post-crisis recovery of the regional economy. The theoretical significance of the study is expressed in the expansion of ideas about the factors of regional resilience.

RESILIENCE ASSESSMENT METHODOLOGIES OF SOCIO-ECONOMIC SYSTEM IN THE CONDITIONS OF GLOBAL INSTABILITY

Purpose. The article aims to substantiate the need to analyze the resilience of a socio-economic system based on “technical”, “environmental”, and “adaptive” approaches. It characterizes the features of the evaluation of a socio-economic system’s resilience against global shocks following the identification of the main resilience parameters. Design/methodology/approach. The author of the article uses the literature review method to explain the importance of the methodological approach to the evaluation of a socio-economic system’s resilience against global shocks, which can be singled out based on economic, innovative, socio-demographic, institutional-managerial, and environmental drivers of economic development. Such scientific research methods as a theoretical-logical explanation, systematization and explanation, and semantic analysis were also applied to study the essence and evaluate the resilience of a socio-economic system. The research is carried out in the framework of institutional economic theory, national economic recovery, and national and regional economies. Findings. The conducted research proves the fact that a socio-economic system’s resilience is a multifaceted concept, while resilience consists of a lot of elements of economic, social, organizationalinstitutional, managerial, environmental, innovative nature, etc. Therefore, resilience cannot evaluated based on one or two parameters or a certain integral index. The article characterizes the measurement of resilience by the volume of a shock the system can withstand (absorb) before it becomes capable to enter a new stability phase. If a new post-shock configuration or condition deteriorates compared to the pre-shock period, a system is assessed as a low-resilience system. Therefore, the system that has managed to enter a new post-shock configuration or its development trajectory is in a better condition compared to the pre-shock period is characterized by high resilience. The article proves the objective necessity to analyze the drivers of organizational and managerial nature since the resilience level is formed under the impact of certain decisions in a socio-economic system’s management, its links to other systems, etc. When evaluating a socio-economic system’s resilience, it is also reasonable to analyze the budget resilience drivers, primarily the observance of balance (prevention of imbalances) between budgetary expenditures and revenues. Therefore, interbudgetary transfers as an essential factor of impact on the resilience, including subsidized regions, should be analyzed when evaluating a system’s resilience. Practical implications. The emphasis on the causal relationship between dependent and independent variables in the course of evaluating the resilience of a socio-economic system is substantiated. The article offers a recursive model, which is more appropriate for the evaluation of “prospective output” to reveal the system’s ability to recover and return to the pre-shock event growth trajectory. Originality/value. The research value lies in the development of a methodological approach to the evaluation of a socio-economic system’s resilience in global instability. The article provides recommendations regarding the application of a multidimensional methodology, which, on the one hand, analyzes the system’s resilience based on the system and holistic approaches and, on the other hand, describes the results of a shock and driving variables with the allocation of individual components of a socio-economic system (economic, social, environmental, managerial, and organizational-institutional, etc.).

MINING AND PRODUCTIVE SPECIALIZATION: ECONOMIC IMPACTS OF THE COLLAPSE OF THE DAM OF FUNDÃO IN MARIANA/BRAZILzil

This paper analyzes the economic impacts in the municipality of Mariana from the Fundão Dam rupture occurred at the end of 2015. The central hypothesis is that economic dependence on the mineral extraction sector makes this municipality more vulnerable to adverse shocks affecting this productive sector, compromising its job recovery capacity. In order to calculate the impacts of this disaster, datas on formal employment estimated through the Synthetic Control Method were used. The results showed that, although Mariana and its synthetic version show similar formal employment trajectory in the pre-shock period, Mariana recovered employability in the second year after the dam rupture, unlike the control group. However, this result is not due to the recovery of formal employment based on sustainable economic diversification strategies, but essentially by dependence of the mining activity and the post-disaster remediation actions that has been gradually implemented in order to recover affected areas.

Trade Adjustment: Worker-Level Evidence *

Abstract We analyze the effect of exposure to international trade on earnings and employment of U.S. workers from 1992 through 2007 by exploiting industry shocks to import competition stemming from China’s spectacular rise as a manufacturing exporter paired with longitudinal data on individual earnings by employer spanning close to two decades. Individuals who in 1991 worked in manufacturing industries that experienced high subsequent import growth garner lower cumulative earnings, face elevated risk of obtaining public disability benefits, and spend less time working for their initial employers, less time in their initial two-digit manufacturing industries, and more time working elsewhere in manufacturing and outside of manufacturing. Earnings losses are larger for individuals with low initial wages, low initial tenure, and low attachment to the labor force. Low-wage workers churn primarily among manufacturing sectors, where they are repeatedly exposed to subsequent trade shocks. High-wage workers are better able to move across employers with minimal earnings losses and are more likely to move out of manufacturing conditional on separation. These findings reveal that import shocks impose substantial labor adjustment costs that are highly unevenly distributed across workers according to their skill levels and conditions of employment in the pre-shock period.

Trade Adjustment: Worker Level Evidence

We analyze the effect of exposure to international trade on earnings and employment of U.S. workers from 1992 through 2007 by exploiting industry shocks to import competition stemming from China's spectacular rise as a manufacturing exporter paired with longitudinal data on individual earnings by employer spanning close to two decades. Individuals who in 1991 worked in manufacturing industries that experienced high subsequent import growth garner lower cumulative earnings, face elevated risk of obtaining public disability benefits, and spend less time working for their initial employers, less time in their initial two-digit manufacturing industries, and more time working elsewhere in manufacturing and outside of manufacturing. Earnings losses are larger for individuals with low initial wages, low initial tenure, and low attachment to the labor force. Low-wage workers churn primarily among manufacturing sectors, where they are repeatedly exposed to subsequent trade shocks. High-wage workers are better able to move across employers with minimal earnings losses, and are more likely to move out of manufacturing conditional on separation. These findings reveal that import shocks impose substantial labor adjustment costs that are highly unevenly distributed across workers according to their skill levels and conditions of employment in the pre-shock period.

Trade Adjustment: Worker Level Evidence

In the past two decades, China’s manufacturing exports have grown spectacularly, U.S. imports from China have surged, but U.S. exports to China have increased only modestly. Using representative, longitudinal data on individual earnings by employer, we analyze the effect of exposure to import competition on earnings and employment of U.S. workers over 1992 through 2007. Individuals who in 1991 worked in manufacturing industries that experienced high subsequent import growth garner lower cumulative earnings and are at elevated risk of exiting the labor force and obtaining public disability benefits. They spend less time working for their initial employers, less time in their initial two-digit manufacturing industries, and more time working elsewhere in manufacturing and outside of manufacturing. Earnings losses are larger for individuals with low initial wages, low initial tenure, low attachment to the labor force, and those employed at large firms with low wage levels. Import competition also induces substantial job churning among high-wage workers, but they are better able than low-wage workers to move across employers with minimal earnings losses, and are less likely to leave their initial firm during a mass layoff. These findings, which are robust to a large set of worker, firm and industry controls, and various alternative measures of trade exposure, reveal that there are significant worker-level adjustment costs to import shocks, and that adjustment is highly uneven across workers according to their conditions of employment in the pre-shock period.

TRAUMA-SHOCK-INDUCED GUT INJURY AND THE PRODUCTION OF BIOLOGICALLY ACTIVE INTESTINAL LYMPH IS ABROGATED BY CASTRATION IN A LARGE ANIMAL PORCINE MODEL

Although small animal rodent studies indicate that there is a sexual dimorphism in the resistance to organ injury after trauma-hemorrhagic shock (T/HS), confirmatory studies are largely lacking in more clinically relevant large animal species. Thus, we tested the hypothesis that castration would reduce the susceptibility of adult minipigs to gut injury and abrogate the production of biologically active intestinal (mesenteric) lymph after T/HS. The hemodynamic response to T/HS was similar between castrated and noncastrated minipigs. Mesenteric lymph collected during the preshock period and in the trauma-sham shock (T/SS) animals did not have increased biological activity. However, T/HS-lymph from the noncastrated males increased the respiratory burst of normal neutrophils, increased endothelial cell monolayer permeability, and was cytotoxic for endothelial cells. Castration abrogated the T/HS-induced neutrophil-activating and endothelial-injurious activities of mesenteric lymph, and the biological activity of the T/HS-lymph from the castrated minipigs was not different from the T/SS animals. As compared with the T/SS minipigs, T/HS increased ileal mucosal injury and intestinal permeability. This increase in gut permeability after T/HS was manifest by in vivo bacterial translocation and by the increased passage of bacteria as well as permeability probes across intestinal segments when tested in the Ussing chamber system. In contrast, neither mucosal injury nor increased intestinal permeability was observed in the castrated minipigs subjected to T/HS. In summary, this large animal porcine study validates the notion that castration limits gut injury and the production of biologically active intestinal lymph after T/HS.

A preliminary study on the monitoring of mixed venous oxygen saturation through the left main bronchus

IntroductionThe study sought to assess the feasibility and accuracy of measuring mixed venous oxygen saturation (SvO2) through the left main bronchus (SpO2trachea)MethodsTwenty hybrid pigs of each sex were studied. After anesthesia, a Robertshaw double-lumen tracheal tube with a single-use pediatric pulse oximeter attached to the left lateral surface was introduced toward the left main bronchus of the pig by means of a fibrobronchoscope. Measurements of SpO2trachea and oxygen saturation from pulmonary artery samples (SvO2blood) were performed with an intracuff pressure of 0 to 60 cmH2O. After equilibration, hemorrhagic shock was induced in these pigs by bleeding to a mean arterial blood pressure of 40 mmHg. With the intracuff pressure maintained at 60 cmH2O, SpO2trachea and SvO2blood were obtained respectively during the pre-shock period, immediately after the onset of shock, 15 and 30 minutes after shock, and 15, 30, and 60 minutes after resuscitation.ResultsSpO2trachea was the same as SvO2blood at an intracuff pressure of 10, 20, 40, and 60 cmH2O, but was reduced when the intracuff pressure was zero (p < 0.001 compared with SvO2blood) in hemodynamically stable states. Changes of SpO2trachea and SvO2blood corresponded with varieties of cardiac output during the hemorrhagic shock period. There was a significant correlation between the two methods at different time points.ConclusionMeasurement of the left main bronchus SpO2 is feasible and provides similar readings to SvO2blood in hemodynamically stable or in low saturation states. Tracheal oximetry readings are not primarily derived from the tracheal mucosa. The technique merits further evaluation.

DECELERATING PRESHOCK SEISMIC DEFORMATION IN FAULT REGIONS DURING CRITICAL PERIODS

We examine the behavior of the intermediate magnitude preshock activity in the fault region of a mainshock during the critical period, that is, in the period when accelerating seismic activity is observed in a broader region (critical region). For this purpose, data concerning 10 recent strong mainshocks (M=6.6-8.3) occurred since 1981 in Greece, Anatolia, Japan and California are used. It is observed that during the critical preshock period, decelerating seismic crustal deformation (Benioff strain) is observed in the fault region (within the fault zone and its close vicinity), whereas accelerating deformation is observed in the broader (critical) region. The dimension of the fault region where decelerating deformation is observed scales positively with the mainshock magnitude and negatively with the mean seismicity rate of this region. The duration of this decelerating deformation scales also negatively with the mean seismicity rate. The physical explanation and importance of these results for earthquake prediction are discussed

Effects of Environmental Enrichment on Rate of Contextual Processing and Discriminative Ability in Adult Rats

The effect of environmental enrichment on conditioned freezing to contextual cues in adult Sprague-Dawley rats was examined. The freezing of both enriched-and standard-reared rats increased with the time spent in the chamber prior to shock. Both groups of rats showed equally low levels of contextual conditioning following a preshock period of 4 s and equally high levels following a 120-s preshock period. However, following a preshock period of 16 s enriched rats displayed more contextual conditioning than standard rats. That is, enriched rats appeared to process contextual information faster than their standard-reared counterparts. Enriched- reared rats also showed a greater ability to discriminate between the conditioning context and a similar but distinctive context. Hence, in addition to forming a representation of the context in memory more rapidly than standard-reared rats, enriched-reared rats also appear to form a more complex representation.

Footshock-induced freezing behavior in rats as a model for assessing anxiolytics

A number of chemically distinct anxiolytics were examined for effects on defensive behavior (foot-shock-induced freezing) in rats. Central nervous system acting drugs which are not anxiolytics were also studied. Animals were injected with a drug or vehicle (IP) prior to being placed in a chamber with a grid floor through which two footshocks were delivered. Behavior was observed during the pre-shock period (2 min) and for 4 min after the second footshock. The effects of the following drugs on the duration of footshock-induced freezing were studied: diazepam (DZP); 2-amino-4,5-(1,2-cyclohexyl)-7 phosphonoheptonic acid (NPC 12626); 3-((+/-)-2-carboxypiperazine-4-yl)-propyl-l-phosphonic acid (CPP); [(+)-5-methyl-10-11,dihydroxy-5H-dibenzo(a,d)cyclohepten-5,10- imine (MK-801); buspirone hydrochloride (BUS); DL-amphetamine sulfate (AMP); haloperidol (HAL); ethyl-beta-carboline-3 carboxylate (beta-CCE). Compounds which reduced the duration of footshock-induced freezing included DZP, BUS, and the competitive NMDA antagonists NPC 12626 and CPP. The non-competitive NMDA antagonist, MK-801, had no effect on the response. The highest dose of amphetamine tested also reduced footshock-induced freezing. However, amphetamine-treated animals did not locomote or rear after footshock, suggesting fear of the environment. Animals injected with DZP, NPC 12626, CPP or buspirone spent at least 1.4 of the 4 post shock minutes locomoting. Haloperidol had no effect on freezing at the doses tested. beta-CCE tended to increase the duration of footshock-induced freezing.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential Response of Substance P-Containing Subtypes of Adrenomedullary Cells to Different Stressors*

Adrenal medullary cells produce not only the catecholamines norepinephrine and epinephrine but also a number of peptides; hence, they can be subclassified according to their peptide quality. The present study was an attempt to test whether different stressors address different subclasses of adrenal medullary cells. The adrenal gland of intact male rats was implanted with a dialysis system, and the jugular vein was catheterized. One day after surgery, the adrenal dialysis system was connected to a perfusion pump, and Ringer solution was used for dialysis; dialysate fractions were collected at 15-min intervals, and blood was withdrawn at the end of each fraction period after a 2-h equilibration period. The basal release rates of pituitary PRL and adrenal corticosterone, measured in plasma, and of epinephrine, norepinephrine, and substance P (SP) measured in the adrenal dialysates, were constant during the preshock period. SP concentrations in the blood were below the detection limit of the RIA. Application of mild electric foot shock stress resulted in a marked increase in adrenal catecholamine and SP release. Plasma PRL and corticosterone levels also rose during the time of exposure to foot shock, but plasma SP concentrations remained at undetectable values. In contrast, a metabolic stress i.e. insulin-induced hypoglycemia, did not affect adrenal SP release, although adrenal catecholamine release increased to a larger degree than after foot shock stress. Plasma PRL and corticosterone levels also increased during insulin-induced hypoglycemia. It is concluded that an exogenous stressor (electric foot shock) activates adrenomedullary cells containing catecholamines and SP, whereas these cells are not activated by the stress of insulin-induced hypoglycemia.

Internal countershock produces myocardial damage and lactate production without myocardial ischemia in anesthetized dogs.

The global myocardial extraction of lactate was measured in 13 halothane anesthetized dogs to assess the effect of electric countershock applied directly to the heart. Seven animals received two countershocks of 30 delivered joules each, while six animals were not shocked but were atrially paced to a rate of 190-200, both with and without occlusion of the vena cava to produce a mean arterial pressure of 40-50 mmHg. All animals had substantially positive lactate extraction in the baseline state (36 +/- 10% for countershock group vs. 41 +/- 3% for pacing group). Myocardial lactate extraction reached a markedly negative nadir 2.5 min after countershock (-19 +/- 15%), but returned toward normal by 6 min (10 +/- 6%). Lactate extraction was not significantly changed from baseline in the pacing group. The relationship between changes in regional myocardial blood flow (radiolabeled microspheres) and post-countershock myocardial damage (technetium pyrophosphate uptake) was assessed in six dogs shocked as above. Mean myocardial blood flow was increased minimally immediately after countershock (0.78 +/- 0.08 ml X min-1 X g-1 vs. 1.16 +/- 0.3), but there was no difference in blood flow between damaged and undamaged tissue at either time point. The epicardial-to-endocardial ratio of blood flow was unchanged after countershock (0.97 +/- 0.05 vs. 0.99 +/- 0.08). There was no relationship between myocardial damage and either the absolute amount of blood flow after countershock (r = -0.03) or the change in blood flow compared with the pre-shock period (r = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Preservation of Myocardial Contractility in Hemorrhagic Shock with Methylprednisolone

The left anterior descending or left circumflex coronary artery was cannulated selectively in 10 dogs. Methylprednisolone, 1 mg per kilogram of body weight, was injected into the artery and the cannula was withdrawn. The animals were then subjected to hemorrhagic shock for 90 minutes. Retransfusion to prestudy blood pressure was then accomplished. The electrocardiogram, arterial blood pressure, contractile force, and first derivative of contractile force were recorded continuously both from the areas that were pretreated and those that were not, the controls. Contractile force in the control area was reduced to 32 ± 3.2% of the preshock period after 90 minutes of shock, whereas in the pretreated area it was twice as high at the same time. Ten minutes after transfusion, the contractile force of the pretreated area exceeded the preshock level, whereas the recovery of contractile force in the control area reached only 70% of the preshock level. This study shows that intracoronary infusion of methylprednisolone can afford myocardial protection in hemorrhagic shock to a significant degree.

Prevention of myocardial depression in experimental hemorrhagic shock by pretreatment with hydrocortisone.

The left anterior descending or left circumflex coronary artery was cannulated in ten dogs. 4 mg/kg hydrocortisone were slowly infused and the cannula was withdrawn. The dogs were then subjected to hemorrhagic shock for 90 minutes followed by retransfusion. The contractile force (CF) and its first derivative (df/dt) were measured in the pretreated (infused) area and in a control (non-perfused) area of the left ventricle. During the shock period, CF and df/dt in the non-pretreated area showed a 50% reduction in comparison to the pre-shock level, whereas the contractile force in the area that had been pretreated with hydrocortisone did not change when compared to the pre-shock period. This study shows that myocardial depression secondary to hemorrhagic shock can be effectively prevented by pretreatment with hydrocortisone.

The role of carbon dioxide in the development of pulmonary insufficiency

The effects of carbon dioxide (PCO2 = 40 versus PCO2 = 20) on pulmonary function changes during 2 hours of hemorrhagic hypotension followed by resuscitation are evaluated in 21 dogs. Pulmonary hemodynamics, mechanics, gas exchange, functional residual capacity, and morphology are studied. In the preshock period, hypocapnia is associated with a decreased cardiac output, increased dead space, and increased alveolar-arterial (A-a) gradiant (room air). During the period of hypotension, all parameters in both groups changed similarly. After resuscitation, the A-a gradients in the two groups further widened. Following the return to control levels of normocapnia in all animals, the group which had been hypocapnic during the hypotensive episode continued to show increased shunting (20 versus 13 percent, p less than 0.05). These results correlated well with cinemicroscopic findings, which showed the normocapnic group to have less interstitial edema and better capillary flow.

Coping behavior, punishment and gastric secretion in the rat

One group of rats could avoid continuous grid shock by depressing a treadle manipulandum. In another group, the escape response was punished by shock administered via the treadle. Chronic gastric cannulas allowed the collection of gastric secretion. Total acid output was not significantly different between shock yoke control rats and their respective experimental mates. Gastric secretion and total acid output were significantly depressed during the shock period as compared to the preshock period, and rats whose coping response was punished secreted less acid as compared to rats which were not punished for eliciting the coping response. Gastric secretion, as a response to environmental stress, is discussed.

Discontinuous shock and generalization to the preshock period in discriminated avoidance learning

Discontinuous shock has been shown to have a facilitating effect upon discriminated bar-press avoidance learning. The effect has been attributed to enhanced generalization of escape responses to the preshock period. Since the factor crucial to enhanced generalization is presumed to be the occurrence of escape responses in the absence of shock, it was hypothesized that presentation of shock in what otherwise would have been off-shock periods, should inhibit avoidance learning. The avoidance performance of animals trained under standard discontinuous shock was compared with that of animals receiving an additional burst of shock contingent upon each escape response. Nonsignificant differences appeared between treatment groups and were in the opposite direction to that expected. It was concluded that rather than producing an increase in generalization, discontinuous shock improves the quality of the response generalized.