A Positive Contrast Effect Following Multiple Shifts

1975 ◽  
Author(s):  
Garvin McCain ◽  
John Cooney
Keyword(s):  
Contrast Effect ◽  
Positive Contrast ◽  
Positive Contrast Effect

Behavioral Contrast in Pigeons with Qualitatively Different Reinforcers

1979 ◽  
Vol 45 (2) ◽  
pp. 535-538 ◽  
Author(s):  
Donald L. Pingrey ◽  
Denis L. Delehanty ◽  
D. Alan Stubbs
Keyword(s):  
Multiple Schedule ◽  
Contrast Effect ◽  
Reinforcement Schedule ◽  
Behavioral Contrast ◽  
Positive Contrast ◽  
Response Rates ◽  
Positive Contrast Effect ◽  
Positive Behavioral Contrast ◽  
Extinction Component

Three white Carneaux pigeons were trained to respond on a mult VI 1-min. (milo reinforcement), VI 1-min. (pea reinforcement) schedule when each component was associated with a different key, feeder, and reinforcer. The experiment was divided into four phases. In Phases 1 and 3, baseline rates of responding were established. In experimental Phases 2 and 4, one component of the multiple schedule was changed to extinction. During the experimental phases, response rates decreased in the extinction component and increased in the unchanged component (positive behavioral contrast). The increase in responding in the unchanged component was greater when the more valued reinforcer was extinguished. These findings are very similar to those reported by Beninger and Kendall (1975) and extend the positive contrast effect to another species, pigeons.

scholarly journals Successive Positive Contrast in One-Way Avoidance Learning

2002 ◽  
Vol 55 (2b) ◽  
pp. 171-184 ◽  
Author(s):  
Antonio Cándido ◽  
Antonio Maldonado ◽  
Alicia Rodríguez ◽  
Alberto Morales
Keyword(s):  
Avoidance Response ◽  
Avoidance Learning ◽  
Contrast Effect ◽  
Positive Contrast ◽  
Warning Signal ◽  
Specific Weight ◽  
Control Group ◽  
Positive Contrast Effect ◽  
Safe Place ◽  
Improved Performance

The main finding of these experiments was a positive contrast effect in one-way avoidance learning. Experiment 1 showed that increasing safety time during one-way avoidance training led to improved performance, surpassing that of a control group that had received the high reward (safe time) from the beginning of training. Experiment 2 showed that a similar positive contrast effect occurred when the time spent in the danger compartment before the onset of the warning signal was shortened. These results suggest that time spent in a safe context acts as a reinforcer of the avoidance response; however, its incentive value depends not only on its duration, but also on the length of the time spent in the danger compartment before the onset of the signal. Overall, results also suggest that the avoidance response is a mixture of flight (motivated by fear) and approach (to a safe place) behaviour. The specific weight of the flight or approach component may be a function of the time and the amount of activation of each emotional state (fear or relief) due to opponent homeostatic compensatory processes that occur in the danger and safe compartments during one-way avoidance learning.

Runway Performance as a Function of Magnitude of Runway Reward and Intertrial Reinforcement

1973 ◽  
Vol 32 (1) ◽  
pp. 331-335 ◽  
Author(s):  
Roger W. Black ◽  
William House ◽  
Jon Moss
Keyword(s):  
Contrast Effect ◽  
Negative Contrast Effect ◽  
Negative Contrast ◽  
Positive Contrast ◽  
Straight Alley ◽  
Positive Contrast Effect ◽  
Runway Performance ◽  
Extended Training ◽  
Runway Trial ◽  
Intertrial Reinforcement

Rats were trained to traverse a straight alley for either 1 or 10 food pellets as reward. Each runway trial was preceded by an intertrial reinforcement of 1 or 10 pellets. A negative contrast effect obtained and persisted throughout the 72 trials conducted. Although there was a strong suggestion of a positive contrast effect throughout training, the effect did not prove reliable. The contrast effect results were interpreted as challenging the view that with extended training ITRs become “irrelevant” to runway reward.

Multiple Shifts in Magnitude of Reward

1981 ◽  
Vol 49 (1) ◽  
pp. 335-338 ◽  
Author(s):  
David T. Goomas
Keyword(s):  
Contrast Effect ◽  
Large Reward ◽  
Small Reward ◽  
Negative Contrast Effect ◽  
Negative Contrast ◽  
Positive Contrast ◽  
Positive Contrast Effect ◽  
Shift Group

Three groups of 5 rats were administered either large reward (10 pellets), small reward (2 pellets), or multiple shifts (Iarge-small-large-etc.) in an alleyway. The multiple-shift group received a total of 7 large and 6 small phases of reinforcement. Early in training the shifted group exhibited positive contrast effect to a shift to large reward and negative contrast effect to a shift to small reward. Later in training, the same group showed neither effect perhaps because experience with the shift provided a smaller discrepancy between the upshifts and downshifts in magnitude of reward.

Effects of Shifts in Delayed Food Reward: Repeated Shifts

1979 ◽  
Vol 45 (1) ◽  
pp. 219-222
Author(s):  
David T. Goomas
Keyword(s):  
Contrast Effect ◽  
Food Reward ◽  
Negative Contrast Effect ◽  
Negative Contrast ◽  
Positive Contrast ◽  
Positive Contrast Effect ◽  
Second Shift

In a repeated-shifts study, a negative contrast effect was obtained when a group of rats was shifted from 0- to 20-sec. delayed food reward only in the first, but not the second, shift. No positive contrast effect was obtained in either shift when a group of rats was shifted from 20- to 0-sec. delayed food reward. Shifts in delay are not repeatedly effective in inducing negative contrast and not effective at all in inducing positive contrast.

Evaluation of Positive Contrast Arthrography in Canine Cranial Cruciate Ligament Disease

1996 ◽  
Vol 09 (01) ◽  
pp. 10-3 ◽  
Author(s):  
D.N. Aron ◽  
R. Roberts ◽  
J. Stallings ◽  
J. Brown ◽  
C.W. Hay
Keyword(s):  
Articular Surface ◽  
Cruciate Ligament ◽  
Positive Contrast ◽  
Joint Effusion ◽  
Radiographic Evaluation ◽  
Cranial Cruciate Ligament ◽  
Joint Pathology ◽  
Meniscal Pathology ◽  
Cranial Cruciate Ligament Disease ◽  
Better Than

SummaryArthrographic and intraoperative evaluations of stifles affected with cranial cruciate disease were compared. Arthrography did not appear to be helpful in predicting cranial cruciate ligament pathology. The caudal cruciate ligament was consistently not visualized in the arthrograms and was normal at surgery. The menisci were visualized consistently in the arthrograms, but conclusions could not be made as to the benefit of arthrography in predicting meniscal pathology. Arthrography was not helpful in predicting joint capsule and femoral articular surface pathology. Survey radiographic evaluation was better than arthrography in evaluating joint pathology. When cruciate injury is suspected, after history and physical examination, survey radiographs are better than positive contrast arthrograms at supporting the diagnosis.Positive contrast arthrography was evaluated as a diagnostic aid in canine cranial cruciate ligament disease. It did not appear to be useful in predicting joint pathology. With arthrography, both menisci could be visualized and evaluated for abnormalities. Joint effusion and presence of osteophytes evaluated on survey radiographs was better than arthrography in evaluating joint pathology.

scholarly journals Positive Contrast Imaging of SPIO Nanoparticles

2012 ◽  
Vol 2012 ◽  
pp. 1-9 ◽  
Author(s):  
Chenghong Lin ◽  
Shuhui Cai ◽  
Jianghua Feng
Keyword(s):  
Negative Contrast ◽  
Superparamagnetic Iron Oxide ◽  
Positive Contrast ◽  
Disease Diagnosis ◽  
Cell Labeling ◽  
Contrast Imaging ◽  
Advantages And Disadvantages ◽  
Tissue Interface ◽  
Dark Signal ◽  
Ideal Method

It is advantageous to achieve positive contrast images instead of negative contrast images in superparamagnetic iron-oxide (SPIO) nanoparticles-based MR imaging in order to distinguish the signal surrounding SPIO nanoparticles from the dark signal due to local field inhomogeneity and the artifacts due to tissue interface and background noise, eliminate the inherent defects in the traditional MRI such as partial-volume effects and large void volume for reliable visualization, and increase contrast-to-noise ratio. Many methods generating positive signal with SPIO nanoparticles have been developed in the last decade. This paper provides an overview of current visualization methods and states their advantages and disadvantages. In practice, these techniques have been widely applied to cell labeling and disease diagnosis and monitoring. However, there is still a need for an ideal method to achieve both accuracy and sensitivity.

Approaches to common conditions of the gastrointestinal tract in pet hamsters

2021 ◽  
Vol 26 (3) ◽  
pp. 20-26
Author(s):  
Vicki Baldrey
Keyword(s):  
Nutritional Support ◽  
Gastrointestinal Disease ◽  
Parasitic Infection ◽  
Positive Contrast ◽  
Abdominal Ultrasound ◽  
Gastrointestinal Diseases ◽  
Indications For Surgery ◽  
Pet Trade ◽  
Free Environment ◽  
The Uk

Hamsters are popular pets in the UK. The Syrian or Golden hamster (Mesocricetus auratus) is the best known species in the pet trade, with a variety of dwarf species also encountered. Gastrointestinal disease occurs frequently, and diarrhoea is a common presenting complaint. This is most often associated with bacterial or parasitic infection, but can also be related to neoplasia or the use of certain antibiotics. Initial stabilisation of the hamster with diarrhoea should include provision of a warm stress-free environment, fluid therapy, nutritional support with an appropriate critical care diet and analgesia. Following a full history and clinical examination, further diagnostic steps include faecal parasitology and microbiology, routine biochemistry and haematology, radiography with or without positive contrast, and abdominal ultrasound. Indications for surgery include evidence of intestinal obstruction or prolapsed intussusception. This article gives an overview of the most common gastrointestinal diseases encountered in hamster species and provides a guide of how to logically approach the investigation and treatment of these cases, achievable in general practice.

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