Prevalence of suicidal ideation in German psychotherapy outpatients: A large multicenter assessment

BACKGROUND

Suicidal ideation is a major concern in clinical practice. Yet, little is known about prevalence rates of suicidal ideation in patients undergoing outpatient psychotherapeutic treatment. Therefore, the aim of the current study is to assess the prevalence of suicidal ideation in a large sample of psychotherapy outpatients in Germany. The data analyzed in this study is taken from the KODAP-project on the coordination of data collection and analysis at German university-based research and training outpatient clinics for psychotherapy.

METHODS

A total of N = 10,357 adult outpatients (64.4 % female; age: M(SD) = 35.94 (13.54), range: 18-92 years of age) starting cognitive-behavioral therapy at one of 27 outpatient clinics in Germany were included in the current study. Prevalence of suicidal ideation was assessed with the Suicide Item (Item 9) of the Beck-Depression Inventory II.

RESULTS

Suicidal ideation was reported by 36.7 % (n = 3795) of the participants. Borderline Personality Disorder, Posttraumatic Stress Disorder, and recurrent Major Depression were the diagnoses most strongly associated with the presence and severity of suicidal ideation.

LIMITATION

Suicide ideation was assessed only with the respective item of the Beck Depression Inventory II.

CONCLUSION

Suicidal ideation is very common among adult patients who start psychotherapy in Germany. A well-founded knowledge of risk assessment in suicidal patients and suicide-specific treatment options is therefore highly relevant.

The role of tacit knowledge in communication and decision-making during emerging public health incidents

Strong communication systems for knowledge exchange are required to prevent, respond to and mitigate the effects of emerging public health incidents (EPHIs). The objective of this paper is to examine how "tacit knowledge" - implicit knowledge used to guide everyday practice - is employed in professional relationships and communication processes between public health and acute care settings. A qualitative study design was used to explore the experiences of key informants from public health and acute care settings in Ontario, Canada, to examine how specific dimensions of tacit knowledge are employed in communications about EPHIs. Twenty-six in-depth interviews were conducted from 2014 to 2015. The results describe the way in which participants employ discretion and knowledge of local context, and rely on relationships built on trust and credibility, to facilitate decision-making and communication during EPHIs. Given the uncertainty characterizing most EPHIs, communicators rely a great deal on their informal knowledge and networks which allow them to remain flexible and respond quickly to changing situations. The results reveal that communication about public health guidance during emergencies is a complex and active process that draws from past experiences of the individuals involved, and is shaped by the requirements of local circumstances. The broader implications of these findings for building resilient and responsive health systems are considered. In particular, for rethinking the authority of standardized forms of evidence in public health decision-making, and the importance of knowledge which is grounded in the uniqueness of specific local contexts.

Elevated Interferon Alpha in the Serum of Laboratory Strains of Mice and Porcine Serum by ELISA

We examined Interferon (IFN)-Alpha and -Beta levels in pooled sera and individual bleeds from C57/Bl, Balb/C and CD-1 mice. 20 Individuals from each strain from two independent colonies were evaluated in commercial assays. The IFN-Beta ELISA detected IFN in 1 of the 60 individuals while the IFN-Alpha assay which detects all 14 subtypes measured IFN in 13 of 60. 5 individuals exhibited greater than 4 pg/ml of IFN-Alpha detected. Specificity was demonstrated by knockdown of the signal using non-biotinylated detection antibody. 14 of 54 porcine sera samples from 4 independent sources were positive for IFN alpha by an ELISA under development, and similar knock-down experiments suggest specificity. This is in contrast to human sera/plasma samples where less than 3% of healthy donor samples have quantifiable IFN-Alpha or -Beta above 0.5 pg/ml. This study may raise questions about the regulation of the IFN system in different species and the potential of these differences to affect experimental results in a variety of models.

Comparison of Interferons and Other Biomarkers in Influenza and Healthy Donor Samples

Toward an understanding of biomarkers for acute viral diseases we have examined Influenza serum in comparison to healthy donors. We determined the levels of Interferon (IFN) Alpha, Beta, Gamma as well as Neopterin and Beta-2 Microglobulin (B2M) by ELISA in the Serum of 38 Influenza and 65 healthy donors using commercial assays. We measured chemokines and proinflammatory cytokines as biomarkers for IFN Activity by electrochemiluminescence. Assays were performed according to the manufacturer’s protocol. IFN-Omega levels were determined using a newly developed ultra-sensitive single molecule assay sensitive to 0.04 pg/ml. Percentile stratification was by Mann-Whitney non-parametric testing and correlations were determined under Spearman conditions. None of the healthy donors exhibited quantifiable IFN-Alpha or Beta and only two had detectable levels of IFN-Omega. Within the Flu cohort, 68.5% of samples contain quantifiable IFN-Alpha and Omega and 39.5% had IFN-Beta. 79% of the Flu samples displayed IFN-Gamma levels above the 95th percentile determined from the healthy donor distribution. Neopterin, B2M, and CXCL-10 were all significantly elevated in the Flu cohort versus the healthy subclass. Other chemokines either showed no correlation or a mild negative correlation. There was a striking concordance between IFN-Alpha and Omega levels. To our knowledge this is the first study to measure IFN-Omega and a broad panel of other analytes in Flu samples. As such this study may provide a beginning to discriminate between different viral diseases.

Cognitive impairment and depression symptoms are independently associated with suicidal ideation in US Veterans

Depression is associated with cognitive impairment and suicidality. The independent association between cognitive impairment and suicidality is less clear. We examined the relationship between suicidal ideation and cognitive impairment in a sample of 50 veterans with depressive disorder diagnoses. Using zero-inflated Poisson regression, the severity of suicidal ideation was negatively associated with attention (incidence rate ratio [IRR] = 0.78, p < .001), memory (IRR = 0.87, p < .001), and total cognition (IRR = 0.90, p = .007) index scores as measured by the Dementia Rating Scale 2 (DRS-2). These three indices continued to significantly predict suicidal ideation severity once depression symptoms were controlled for.

Public Health Efforts Can Impact Adoption of Current Susceptibility Breakpoints, but Closer Attention from Regulatory Bodies Is Needed

Microbiological testing, including interpretation of antimicrobial susceptibility testing results using current breakpoints, is crucial for clinical care and infection control. Continued use of obsolete Enterobacteriaceae carbapenem breakpoints is common in clinical laboratories. The purposes of this study were (i) to determine why laboratories failed to update breakpoints and (ii) to provide support for breakpoint updates. The Los Angeles County Department of Public Health conducted a 1-year outreach program for 41 hospitals in Los Angeles County that had reported, in a prior survey of California laboratories, using obsolete Enterobacteriaceae carbapenem breakpoints. In-person interviews with hospital stakeholders and customized expert guidance and resources were provided to aid laboratories in updating breakpoints, including support from technical representatives from antimicrobial susceptibility testing device manufacturers. Forty-one hospitals were targeted, 7 of which had updated breakpoints since the prior survey. Of the 34 remaining hospitals, 27 (79%) assumed that their instruments applied current breakpoints, 17 (50%) were uncertain how to change breakpoints, and 10 (29%) lacked resources to perform a validation study for off-label use of the breakpoints on their systems. Only 7 hospitals (21%) were familiar with the FDA/CDC Antibiotic Resistance Isolate Bank. All hospitals launched a breakpoint update process; 16 (47%) successfully updated breakpoints, 12 (35%) received isolates from the CDC in order to validate breakpoints on their systems, and 6 (18%) were planning to update within 1 year. The public health intervention was moderately successful in identifying and overcoming barriers to updating Enterobacteriaceae carbapenem breakpoints in Los Angeles hospitals. However, the majority of targeted hospitals continued to use obsolete breakpoints despite 1 year of effort. These findings have important implications for the quality of patient care and patient safety. Other public health jurisdictions may want to utilize similar resources to bridge the patient safety gap, while manufacturers, the FDA, and others determine how best to address this growing public health issue.

An Exploratory Study of Exercise-related Effects on Memory and Hippocampal Connectivity in Schizophrenia

Memory impairment in schizophrenia has been linked to abnormal functioning of fronto-temporal networks. In this pilot study, we investigated whether 12-weeks of exercise improved hippocampal-dependent memory functions and resting-state functional connectivity in middle-aged adults with schizophrenia. The exercise regimen was feasible, well-attended, and safe. There was a pre- to post-intervention increase in spatial memory accuracy that was correlated to an increase in hippocampal-prefrontal cortex connectivity. No increase was found in pattern separation performance or hippocampal volume. A controlled trial is needed to replicate these findings and elucidate the functional brain networks underlying exercise-induced cognitive improvement in schizophrenia.

A Phase 1 study of ARQ 087, an oral pan-FGFR inhibitor in patients with advanced solid tumours

Background:

ARQ 087 is an orally administered pan-FGFR inhibitor with multi-kinase activity. This Phase 1 study evaluated safety, pharmacokinetics, and pharmacodynamics of ARQ 087 and defined the recommended Phase 2 dose (RP2D).

Methods:

Patients with advanced solid tumours received ARQ 087 administered initially at 25 mg every other day and dose-escalated from 25 to 425 mg daily (QD) continuous dosing. FGF19, 21, 23, and serum phosphate were assessed as potential biomarkers of target engagement.

Results:

80 patients were enrolled, 61 in dose-escalation/food-effect cohorts and 19 with pre-defined tumour types in the expansion cohort. The most common ARQ 087-related adverse events were fatigue (49%), nausea (46%), aspartate aminotransferase (AST) increase (30%), and diarrhoea (23%). Four patients (5%) experienced grade 1 treatment-related hyperphosphataemia. Dose-limiting toxicity was reversible grade 3 AST increase. The RP2D was 300 mg QD. Pharmacokinetics were linear and dose-proportional from 25 to 325 mg QD, and were unaffected by food. Statistically significant changes (P-value<0.05) suggest phosphate and FGF19 levels as markers of target engagement. In 18 evaluable patients with FGFR genetic alterations, 3 confirmed partial responses (two intrahepatic cholangiocarcinomas (iCCA) with FGFR2 fusions and one urothelial cancer with FGFR2 and FGF19 amplification) and two durable stable disease at ⩾16 weeks with tumour reduction (FGFR2 fusion-positive iCCA and adrenocortical carcinoma with FGFR1 amplification) were observed.

Conclusions:

ARQ 087 had manageable toxicity at the RP2D of 300 mg QD, showed pharmacodynamics effects, and achieved objective responses, notably in patients with FGFR2 genetic alterations.

A pilot study of the trauma recovery group for veterans with post traumatic stress disorder and co-occurring serious mental illness

BACKGROUND

Many Veterans may not benefit from gold-standard evidence-based treatments for post-traumatic stress disorder (PTSD) because they suffer from co-occurring serious mental illness (SMI).

AIMS

This pilot study is the first to evaluate the feasibility and preliminary effectiveness of the Trauma Recovery Group in a sample of Veterans with PTSD and SMI.

METHODS

Fourteen Veterans with PTSD and SMI were enrolled in a 21-session group-based cognitive behavioral therapy program targeting PTSD. The PTSD Checklist was the primary outcome measure; secondary outcomes included the Participant Health Questionnaire, the Post Traumatic Cognitions Inventory, and the Beck Cognitive Insight Scale.

RESULTS

Seventy-one percent of participants completed the trial. The intervention was associated with a significant reduction of PTSD symptoms and a trend-level reduction of maladaptive post-traumatic cognitions. There was a significant positive correlation between change in PTSD symptoms and change in post-traumatic cognitions.

CONCLUSIONS

The findings support the feasibility and preliminary effectiveness of the Trauma Recovery Group for Veterans with co-occurring PTSD and SMI, and suggest that controlled research on the program is warranted.

Evaluation of STAT medication ordering process in a community hospital

Background:

In most health care facilities, problems related to delays in STAT medication order processing time are of common concern.

Objective:

The purpose of this study was to evaluate processing time for STAT orders at Kimball Medical Center.

Methods:

All STAT orders were reviewed to determine processing time; order processing time was also stratified by physician order entry (physician entered (PE) orders vs. non-physician entered (NPE) orders). Collected data included medication ordered, indication, time ordered, time verified by pharmacist, time sent from pharmacy, and time charted as given to the patient.

Results:

A total of 502 STAT orders were reviewed and 389 orders were included for analysis. Overall, median time was 29 minutes, IQR 16–63; p<0.0001.). The time needed to process NPE orders was significantly less than that needed for PE orders (median 27 vs. 34 minutes; p=0.026). In terms of NPE orders, the median total time required to process STAT orders for medications available in the Automated Dispensing Devices (ADM) was within 30 minutes, while that required to process orders for medications not available in the ADM was significantly greater than 30 minutes. For PE orders, the median total time required to process orders for medications available in the ADM (i.e., not requiring pharmacy involvement) was significantly greater than 30 minutes. [Median time = 34 minutes (p<0.001)].

Conclusion:

We conclude that STAT order processing time may be improved by increasing the availability of medications in ADM, and pharmacy involvement in the verification process.

Sleep health literacy in head start families and staff: exploratory study of knowledge, motivation, and competencies to promote healthy sleep

CONTEXT

Healthy child development requires sufficient, quality sleep. Sleep problems in early childhood impair social-emotional and cognitive function and increase obesity risk. From a health literacy framework, "sleep health literacy" denotes the knowledge, motivation, and competencies to promote healthy sleep and to recognize a sleep problem.

DESIGN

To explore the untapped potential of early childhood education (ECE) programs to promote sleep health literacy, we surveyed staff (n=63) and parents (n=196) in Head Start about sleep-related knowledge, attitudes/beliefs, sleep hygiene, and sleep problems. Head Start is the largest ECE program in the United States.

RESULTS

Most parents believed that their child had healthy sleep habits (81%); few believed that he or she had a sleep problem (10%). Yet, unhealthy bedtime practices and insufficient sleep for age were reported in 50% and 33% of children, respectively. Between 10% and 12% of children had 1 or more sleep onset or awakening problems. Every unhealthy bedtime practice but one was associated with a sleep problem; parental presence at bedtime was associated with the most problems. Insufficient sleep was significantly associated with unhealthy sleep practices. More children with late vs early bedtimes (48% vs14%, P < .01) and frequent vs less frequent parental presence at bedtime (50% vs 26%-30%, P < .02) failed to obtain sufficient sleep. Staff members are more comfortable discussing healthy sleep with parents (87%) than counseling them (45%).

CONCLUSION

Among parents, there is a "disconnect" between actual and perceived sleep hygiene. Similarly, staff perceived a gap between their competencies to promote healthy sleep in families and their capacity to address sleep problems. US health literacy goals include the need to embed accurate, accessible, and actionable health information in ECE programs. Study findings strongly support the need to work toward sleep health literacy in ECE programs.

GeSn/Ge multiquantum well photodetectors on Si substrates

Vertical incidence GeSn/Ge multiquantum well (MQW) pin photodetectors on Si substrates were fabricated with a Sn concentration of 7%. The epitaxial structure was grown with a special low temperature molecular beam epitaxy process. The Ge barrier in the GeSn/Ge MQW was kept constant at 10 nm. The well width was varied between 6 and 12 nm. The GeSn/Ge MQW structures were grown pseudomorphically with the in-plane lattice constant of the Ge virtual substrate. The absorption edge shifts to longer wavelengths with thicker QWs in agreement with expectations from smaller quantization energies for the thicker QWs.

Evaluating the students' perspectives of a clinic mentoring programme

The purpose of this article is to describe and examine the effectiveness of a mentoring program for third and fourth year clinical dental students. This is an educational intervention for the pre-doctoral students at the Schulich School of Dentistry. We have recently instituted this program and have developed a questionnaire to assess the student perspectives using a SWOT analysis of the strengths, weaknesses, opportunities and threats of this intervention by analyzing the quantitative and qualitative responses of the students towards their clinical education and patient management. Our findings, both quantitative and qualitative, indicated that the mentoring program was well received by most students who would like to see the program expanded. The majority of students felt that the mentoring program aligned well with comprehensive care of their patients while enhancing their clinical experience. One of the strongest areas of agreement involved the ability to discuss cases in a non-threatening environment. The SWOT analysis identified key areas for future improvements. We offer steps to successfully implement a similar program based on our findings. It is our hope that our results might be instrumental for other schools wishing to adopt a similar model which supports patient-based comprehensive care.

A phase I dose escalation study of oral c-MET inhibitor tivantinib (ARQ 197) in combination with gemcitabine in patients with solid tumors

BACKGROUND

Tivantinib (ARQ 197) is an orally available, non-adenosine triphosphate competitive, selective c-MET inhibitor. The primary objective of this study was to evaluate the safety, tolerability and to establish the recommended phase II dose (RP2D) of tivantinib and gemcitabine combination.

PATIENTS AND METHODS

Patients with advanced or metastatic solid tumors were treated with escalating doses of tivantinib (120-360 mg capsules) in combination with gemcitabine (1000 mg/m(2) weekly for 3 of 4 weeks). Different schedules of administration were tested and modified based on emerging preclinical data. Tivantinib was given continuously, twice a day (b.i.d.) for 2, 3 or 4 weeks of a 28-day cycle or on a 5-day on, 2-day off schedule (the day before and day of gemcitabine administration).

RESULTS

Twenty-nine patients were treated with gemcitabine and escalating doses of tivantinib: 120 mg b.i.d. (n = 4), 240 mg b.i.d. (n = 6) and 360 mg b.i.d. (n = 19). No dose-limiting toxicities were observed in escalation. The RP2D was 360 mg b.i.d. daily, and 45 additional patients were enrolled in the expansion cohort. Grade ≥3 treatment-related toxicities were observed in 54 of 74 (73%) patients with the most common being neutropenia (43%), anemia (30%), thrombocytopenia (28%) and fatigue (15%). There was one treatment-related death due to neutropenia. Administration of gemcitabine did not affect tivantinib concentration. Fifty-six patients were assessable for response. Eleven (20%) patients achieved a partial response and 26 (46%) had stable disease (SD), including 15 (27%) who achieved SD for over 4 months. Ten of 37 patients with clinical benefit had prior exposure to gemcitabine.

CONCLUSION

The combination of tivantinib at its monotherapy dose and standard dose gemcitabine was safe and tolerable. Early signs of antitumor activity may warrant further development of this combination in nonsmall-cell lung cancer, ovarian, pancreatic and cholangiocarcinoma.

CLINICALTRIALSGOV IDENTIFIER

NCT00874042.

A Phase-1b study of tivantinib (ARQ 197) in adult patients with hepatocellular carcinoma and cirrhosis

BACKGROUND

The mesenchymal-epithelial transition factor (MET) receptor is dysregulated in hepatocellular carcinoma (HCC), and tivantinib (ARQ 197) is an oral, selective, MET inhibitor.

METHODS

This Phase-1b study assessed tivantinib safety as primary objective in patients with previously treated HCC and Child-Pugh A or B liver cirrhosis. Patients received oral tivantinib 360 mg twice daily until disease progression or unacceptable toxicity.

RESULTS

Among 21 HCC patients, common drug-related adverse events (AEs) were neutropaenia, anaemia, asthenia, leucopaenia, anorexia, diarrhoea, and fatigue. No drug-related worsening of liver function or performance status occurred, but one Child-Pugh B patient experienced drug-related bilirubin increase. Four patients had drug-related serious AEs, including one neutropaenia-related death. Haematologic toxicities were more frequent than in previous tivantinib studies but were manageable with prompt therapy. Best response was stable disease (median, 5.3 months) in 9 of 16 evaluable patients (56%). Median time to progression was 3.3 months.

CONCLUSION

Tivantinib demonstrated a manageable safety profile and preliminary antitumour activity in patients with HCC and Child-Pugh A or B cirrhosis.

Mechanisms linking obesity, inflammation and altered metabolism to colon carcinogenesis

Due to its prevalence, obesity is now considered a global epidemic. It is linked to increased risk of colorectal cancer, the third most common cancer and the second leading cause of death among adults in Western countries. Obese adipose tissue differs from lean adipose tissue in its immunogenic profile, body fat distribution and metabolic profile. Obese adipose tissue releases free fatty acids, adipokines and many pro-inflammatory chemokines. These factors are known to play a key role in regulating malignant transformation and cancer progression. Obese adipose tissue is infiltrated by macrophages that participate in inflammatory pathways activated within the tissue. Adipose tissue macrophages consist of two different phenotypes. M1 macrophages reside in obese adipose tissue and produce pro-inflammatory cytokines, and M2 macrophages reside in lean adipose tissue and produce anti-inflammatory cytokines, such as interleukin-10 (IL-10). The metabolic networks that confer tumour cells with their oncogenic properties, such as increased proliferation and the ability to avoid apoptosis are still not well understood. We review the interactions between adipocytes and immune cells that may alter the metabolism towards promotion of colorectal cancer.

Short communication: adhesion pathways utilized by HIV-infected lymphocytes

We recently reported a novel adhesion pathway in lymphocytes that is mediated by cyclin-dependent kinase (Cdk) 4 activity and mediates lymphocyte interactions with endothelial matrix. We now demonstrate that HIV-infected lymphocytes also use Cdk4 to mediate spontaneous adhesion to fibronectin and endothelial matrix. We further demonstrate that HIV-infected lymphocytes require Rap-1 activity for phorbol-stimulated adhesion. Understanding adhesion pathways used by HIV-infected lymphocytes may lead to interventions to regulate aberrant adhesion and migration.

Emergency Medical Services: a resource for victims of domestic violence?

BACKGROUND

Domestic violence (DV), also known as intimate partner violence (IPV), is one of the leading causes of serious injury among women of childbearing age. As first responders on the scene during DV calls where personal injuries have occurred, Emergency Medical Services (EMS) could routinely identify, report and assist victims of violence. Yet, little is known of the prevalence of DV calls in EMS practice, Emergency Medical Technicians' (EMT) knowledge and comfort in responding to such calls, or how they care for victims.

METHOD

The objectives of this study were to assess EMTs' knowledge of and experience with providing care to victims of DV in the province of Ontario, Canada. Data were gathered through an online, short-answer survey. Survey data were analysed using basic frequency displays, and descriptive statistics are reported.

RESULTS

Almost 500 EMTs participated in this study, the vast majority of whom (90%) attended at least one DV call in the preceding year, with 65% attending between 10 and 20 DV calls. The majority of respondents (84.5%) wished for more education and training on the issue.

CONCLUSION

EMTs have frequent contact with victims of DV yet have received little education about the issue. The majority of those surveyed would like specific education and training on DV.

Heart rate monitoring as a reliable tool for assessing energy expenditure in obese individuals

Previous studies have suggested the use of the FlexHR method for predicting daily energy expenditure in various populations. We investigated the stability of the relation between oxygen consumption (VO2) and heart rate (HR) in obese subjects undergoing a fitness and weight reduction program. Eleven obese (BMI>30) healthy subjects (6 males, 5 females) were recruited from a Wellness program. Subjects performed a laboratory calibration procedure between HR and VO2 in resting and exercising conditions, before starting the Wellness program (Stage I) and after reducing 10% of their initial body weights (BW) within 6 months (Stage II). Mean BW, BMI and % body fat were reduced by 13.1±4.4 kg, 4.2±1.4 kg.m-2 and 6.8±4.1%, respectively, for all parameters (P<0.001). Mean peak VO2 increased from 31.3±7.1 at the beginning to 37.2±7.3 mL.kg-1.min-1 at the end of the intervention period (P<0.01). The mean flex HR point changed from 96±14 to 86±15 beats.min-1 (P<0.05). There were no significant individual differences in the HR-VO2 prediction equations derived from the laboratory calibrations in either stage. In conclusion, the relationship between HR and VO2 consumption remains stable during a time period of weight reduction. The use of the FlexHR method for predicting energy expenditure by heart rate monitoring is recommended for subjects undergoing a weight-reduction program. It should be taken in account, however, that an increase in aerobic capacity, in parallel to changes in body weight and composition, might cause a decrease in the flex point.

Studies of operant and reflexive key pecks in the pigeon

The duration of pigeons' key pecks was studied in three experiments. Experiment I revealed that key pecks early in exposure to continuous reinforcement were of short duration, as were key pecks observed on an omission procedure in which pecks prevented food delivery. Key pecks later in exposure to continuous reinforcement, and those that occurred on positive automaintenance procedures, were of long duration. In Experiment II, pigeons were exposed to fixed-interval and fixed-ratio reinforcement schedules, and durations were recorded separately for each quarter of each interval or ratio. On fixed interval, durations were shorter in the first quarter of each interval than in subsequent quarters; on fixed ratio, durations were longer in the first quarter of the ratio than in subsequent quarters. These data parallel observations of concurrent operant responding and salivation in dogs. In Experiment III, pigeons were exposed to a discrete trial, differential-reinforcement-of-low-rate 6-sec schedule. Durations of responses in the first 2 sec of the trial were substantially shorter than those of responses that occurred later. The data from all three experiments support the view that the pigeon's "key peck" actually consists of two subclasses of peck, one reflexive and one operant.

Two types of pigeon key pecking: suppression of long- but not short-duration key pecks by duration-dependent shock

The key pecking of eight pigeons was maintained on a variable-interval 1-minute schedule of food reinforcement. Sometimes, all responses between 35 and 50 milliseconds in duration produced a shock; sometimes, all responses between 10 and 25 milliseconds produced a shock; sometimes, shocks were produced by pecks without regard to duration (nondifferential punishment), and sometimes shocks were delivered independently of responding. Punishment of 35- to 50-millisecond responses selectively suppressed those responses, while punishment of 10- to 25-millisecond responses and nondifferential punishment suppressed responding overall but did not suppress responses of particular duration. Punishment of 35- to 50-millisecond responses suppressed key pecking slightly less than did nondifferential punishment. Punishment of 10- to 25-millisecond responses and response-independent shock produced roughly equal amounts of suppression, substantially less than the other punishment procedures. The data support the view that there are at least two kinds of key peck, identifiable on the basis of duration, one of which (short duration) is insensitive to its consequences.

Stimulus-reinforcer contingencies and local behavioral contrast

Four pigeons were exposed to a series of multiple schedules of variable-interval reinforcement in which pecks were required on one key (operant key) and components were signalled on a second key (signal key). Four additional pigeons experienced identical conditions, except that a yoking procedure delivered food on variable-time schedules, with no key pecks required. One of the components of the multiple schedule was constant throughout the experiment as a variable-interval (or variable-time) 30-second schedule. Operant-key responding during the constant component was uniform throughout the component, uninfluenced by changes in the duration of the variable component, and only slightly influenced by changes in reinforcement frequency correlated with the variable component. By comparison, signal-key response rate during the constant component was highest at the onset of the component, was higher when the variable component was 60-sec long than when it was 1-sec long, and was higher when no reinforcement occurred in the variable component than when reinforcement was scheduled in the variable component. These characteristics of signal-key pecking matched characteristics of local positive behavioral contrast. These data are taken to support the "additivity theory" of behavioral contrast and to suggest that Pavlovian stimulus-reinforcer relations contribute primarily to the phenomenon of local positive contrast.

Effects of reinforcement magnitude on pigeons' preference for different fixed-ratio schedules of reinforcement

In concurrent, two-member chains, the completion of one or the other of two initial percentage fixed-interval 90-sec links produced a terminal link in which the completion of a fixed ratio produced food reinforcement. The fixed ratios and the duration of reinforcement in the terminal links were varied. Relative response rate in initial links was proportional to the relative reinforcement duration per ratio response (reinforcement duration divided by fixed ratio) in terminal links. The rate of responding in the terminal fixed-ratio links was insensitive to both ratio size and reinforcement duration and therefore did not vary sufficiently to distinguish between responses per reinforcement and immediacy of reinforcement as controlling variables in terminal links.