Stability and variability in extinction.

Some studies have found that extinction leaves response structures unaltered; others have found that response variability is increased. Responding by Long-Evans rats was extinguished after 3 schedules. In one, reinforcement depended on repetitions of a particular response sequence across 3 operanda. In another, sequences were reinforced only if they varied. In the third, reinforcement was yoked: not contingent upon repetitions or variations. In all cases, rare sequences increased during extinction— variability increased—but the ordering of sequence probabilities was generally unchanged, the most common sequences during reinforcement continuing to be most frequent in extinction. The rats' combination of generally doing what worked before but occasionally doing something very different may maximize the possibility of reinforcement from a previously bountiful source while providing necessary variations for new learning. The main goal of the present study is to reconcile two competing accounts of extinction. One is that variability increases during extinction of operant responses. Another is that operant structures, manifest in response topographies, sequences, and distributions, are unaffected by extinction and remain intact. How can structure

Food Use and Health Effects of Soybean and Sunflower Oils

This review provides a scientific assessment of current knowledge of health effects of soybean oil (SBO) and sunflower oil (SFO). SBO and SFO both contain high levels of polyunsaturated fatty acids (PUFA) (60.8 and 69%, respectively), with a PUFA:saturated fat ratio of 4.0 for SBO and 6.4 for SFO. SFO contains 69% C18:2n-6 and less than 0.1% C18:3n-3, while SBO contains 54% C18:2n-6 and 7.2% C18:3n-3. Thus, SFO and SBO each provide adequate amounts of C18:2n-6, but of the two, SBO provides C18:3n-3 with a C18:2n-6:C18:3n-3 ratio of 7.1. Epidemiological evidence has suggested an inverse relationship between the consumption of diets high in vegetable fat and blood pressure, although clinical findings have been inconclusive. Recent dietary guidelines suggest the desirability of decreasing consumption of total and saturated fat and cholesterol, an objective that can be achieved by substituting such oils as SFO and SBO for animal fats. Such changes have consistently resulted in decreased total and low-density-lipoprotein cholesterol, which is thought to be favorable with respect to decreasing risk of cardiovascular disease. Also, decreases in high-density-lipoprotein cholesterol have raised some concern. Use of vegetable oils such as SFO and SBO increases C18:2n-6, decreases C20:4n-6, and slightly elevated C20:5n-3 and C22:6n-3 in platelets, changes that slightly inhibit platelet generation of thromboxane and ex vivo aggregation. Whether chronic use of these oils will effectively block thrombosis at sites of vascular injury, inhibit pathologic platelet vascular interactions associated with atherosclerosis, or reduce the incidence of acute vascular occlusion in the coronary or cerebral circulation is uncertain. Linoleic acid is needed for normal immune response, and essential fatty acid (EFA) deficiency impairs B and T cell-mediated responses. SBO and SFO can provide adequate linoleic acid for maintenance of the immune response. Excess linoleic acid has supported tumor growth in animals, an effect not verified by data from diverse human studies of risk, incidence, or progression of cancers of the breast and colon. Areas yet to be investigated include the differential effects of n-6- and n-3-containing oil on tumor development in humans and whether shorter-chain n-3 PUFA of plant origin such as found in SBO will modulate these actions of linoleic acid, as has been shown for the longer-chain n-3 PUFA of marine oil

Operant Variability and the Evolution of Volition

Volition has been debated for thousands of years:  what is it, how is it possible for biophysical beings to behave in a voluntary manner, indeed, does volition exist?  Evolution of volition has rarely been part of the discussion.  In this paper, I argue that operant-conditioning studies provide evidence for evolved volition.  Three attributes are common to operant and voluntary behaviors.  One is that responses are goal-directed, purposeful, some say rational, or controlled by reinforcing consequences.  A second is that the responses vary – from random-like to repetitive – with predictability (or unpredictability) depending upon contexts and consequences.  A third attribute is that responses appear to be self-generated or, in operant terms, emitted.  These attributes are found in many species, simple to complex, but species also differ in details.  Taken together, the evidence supports an evolutionary basis of volition

Operant Variability and the Evolution of Volition

Volition has been debated for thousands of years:  what is it, how is it possible for biophysical beings to behave in a voluntary manner, indeed, does volition exist?  Evolution of volition has rarely been part of the discussion.  In this paper, I argue that operant-conditioning studies provide evidence for evolved volition.  Three attributes are common to operant and voluntary behaviors.  One is that responses are goal-directed, purposeful, some say rational, or controlled by reinforcing consequences.  A second is that the responses vary – from random-like to repetitive – with predictability (or unpredictability) depending upon contexts and consequences.  A third attribute is that responses appear to be self-generated or, in operant terms, emitted.  These attributes are found in many species, simple to complex, but species also differ in details.  Taken together, the evidence supports an evolutionary basis of volition

Operant Variability and the Evolution of Volition

Volition has been debated for thousands of years: what is it, how is it possible for biophysical beings to behave in a voluntary manner, indeed, does volition exist? Evolution of volition has rarely been part of the discussion. In this paper, I argue that operant-conditioning studies provide evidence for evolved volition. Three attributes are common to operant and voluntary behaviors. One is that responses are goal-directed, purposeful, some say rational, or controlled by reinforcing consequences. A second is that the responses vary – from random-like to repetitive – with predictability (or unpredictability) depending upon contexts and consequences. A third attribute is that responses appear to be self-generated or, in operant terms, emitted. These attributes are found in many species, simple to complex, but species also differ in details. Taken together, the evidence supports an evolutionary basis of volition.</jats:p