Use of Sub-Atmospheric Pressure Storage to Improve the Quality and Shelf-Life of Marmande Tomatoes cv. Rojito.

In this study, the feasibility of storing Marmande tomatoes (Solanum lycopersicum, cv Rojito) under hypobaric conditions was evaluated. The fruits were sorted into four lots of 72 fruits each. One lot was considered as a control, and the fruits were kept in the open box, while the fruits of the rest of the three remaining lots were enclosed in airtight containers and subjected to 101, 75 and 50 Kpa, respectively. Control fruits and airtight containers were kept at room temperature, and every three days from the beginning of the experiment the following main quality parameters were analysed: ethylene production rate, firmness, colour, total solids content, ascorbic acid, total phenolics and pigments, as well as a sensory analysis carried out by panellists. The results show that sub-atmospheric storage led a reduction in ethylene production, which was associated with a delay in ripening. The differences in the evolution of pigments were very significant, while a large degradation of chlorophylls was observed in the control fruits and in those kept at 101 kPa, in the fruits kept at 75 kPa and 50 kPa the degradation was much slower. In relation to carotenoid pigments, it was observed that sub-atmospheric treatments delayed their appearance compared to control and 101 kPa fruits. In relation to other quality parameters, it was found that control fruit and fruit held at 101 kPa softened more rapidly than fruit under sub-atmospheric conditions, whose loss of firmness was more gradual with differences found only at 9 and 12 days of storage with respect to fruit firmness at harvest. The appearance of these fruits was evaluated with the same score as at the time of harvesting, during 9 of the 12 days of the experiment, then a positive effect of sub-atmospheric treatments was also found in the sensory analysis. The results suggest that sub-atmospheric storage could be a suitable method of increasing the shelf-life of fruits.

The effects of stimulus pre-exposure and conditioning on overt visual attention.

Three experiments (a, b, c) combined to provide a well-powered examination of the effects of stimulus pre-exposure and conditioning on visual attention using an eye tracker and a space-shooter video game where a colored flashing light predicted an attacking spaceship. In each, group "control" received no pre-exposure to the light, group "same" received pre-exposure in the same context as conditioning, and group "different" received pre-exposure in a different context. Experiments differed in visual details regarding the game (1a vs. 1b and 1c) or minor details in the setup of the eye tracker (1a and 1b vs. 1c). Overall, pre-exposure retarded acquisition of keyboard responding. That effect was enhanced, rather than attenuated, by a context change. Separating participants by sign and goal trackers showed the context change enhanced the pre-exposure effect in goal trackers and reduced it in sign trackers. Visual attention to the light declined during pre-exposure and did not recover with either conditioning or a context switch. Visual attention to the light decreased during conditioning. Visual goal tracking toward where the spaceship would appear was also retarded with pre-exposure. Unlike the keyboard responding, a context change led to more normal goal-tracking acquisition. Results are discussed in terms of theories of attention and the potential effects of demand characteristics on the task. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Response reduction and stimulus pre-exposure effects in a human conditioning method.

Two experiments with humans determined whether reduced conditioning following pre-exposure to the conditioned stimulus could be explained by conditioned inhibition (Experiment 1 [E1]) or extinction of responding that the conditioned stimulus (CS) might elicit during pre-exposure (Experiment 2 [E2]). In a video game task (Nelson et al., 2014), participants learned to respond to lights that signaled attacking spaceships. In E1, a red light was either pre-exposed or not pre-exposed between groups prior to conditioning with a green light. Summation tests of red combined with green produced no evidence of conditioned inhibition. In E2, participants received either no pre-exposure to the light, exposure in the same context in which the conditioning would occur, or exposure in a different context. These conditions were factorially combined with whether the light and spaceship were similar (same color) or dissimilar (different colors). In the similar conditions, the light elicited weak responding during pre-exposure, which extinguished. Such extinction did not occur in the dissimilar conditions. Conditioning occurred more rapidly in the similar conditions than in the dissimilar ones, but both conditions showed an equivalent context-dependent pre-exposure effect. Pre-exposure reduced conditioning regardless of whether it reduced responding prior to conditioning. The data are consistent with animal research (Lubow et al., 1968) showing no relation between responding during pre-exposure and the effects of stimulus pre-exposure. Theories which account for the effects of stimulus pre-exposure are discussed, with the conclusion that the data are most consistent with the ideas presented by Wagner (1981). (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Extinction contexts fail to transfer control: Implications for conditioned inhibition and occasion-setting accounts of renewal.

The renewal effect is often explained as a side effect of the extinction context acting as a negative occasion setter. Four experiments tested whether extinction contexts show the selective-transfer property of occasion setters. Experiments 1-3 used a predictive judgment task where participants rated the probability of certain foods (cues) producing gastric malaise (outcomes) in different restaurants (contexts). Experiment 4 used a behavioral suppression task where sensor lights (cues) served as signals to suppress firing responses in certain galaxies (contexts). All 4 (Experiments 1-4) addressed whether a potentially negative occasion-setting context transferred its modulatory power to an extinguished (presumably occasion set) target in the test phase of an ABC renewal design. Experiments 2-4 further assessed the possibility that the extinction context acts as a conditioned inhibitor by testing a simple excitor on a context where extinction occurred. Neither selective (occasion-setting) nor nonselective transfer (conditioned inhibition) was demonstrated. Implications for theories of renewal and occasion-setting are discussed. (PsycInfo Database Record (c) 2020 APA, all rights reserved).

Conditioned anticipatory outcome searching in humans.

Two experiments used eye tracking to examine visual searching for expected outcomes in humans during an associative-learning task. In both, participants learned to press keys on a keyboard to activate weapons to repel invading spaceships in the presence of predictive "sensors." In both experiments, eye tracking showed that participants came to direct their overt visual attention to the portions of the screen where the spaceship would arrive during the presentation of the sensor in a cue-specific manner. Participants also directed attention to the weapon that was used to repel the spaceship. The same results were observed regardless of whether participants were responding on the keyboard, or not (Experiment 2). Pupil dilations occurred to the appearance of the spaceship from the first trial and occurred to the predictive sensor stimuli on later trials in both experiments, suggesting that they might be conditioned responses. In Experiment 2 participants again looked for the expected outcome, but dilations to the predictive stimuli were shown to be an artifact of responding and not due to conditioning. The discussion involves the implications for investigating attention to predictive stimuli using eye trackers, roles of context in behavior, and the utility of outcome searching and pupil dilations as indexes of learning.

Evaluation of physicochemical properties and enzymatic activity of organic substrates during four crop cycles in soilless containers.

BACKGROUND: Organic soilless production in containers requires substrates with appropriate physicochemical and biological properties to ensure that production is sustainable and profitable for several production cycles. The main objective of this study was to comprehensively evaluate these properties in three different mixtures of organic substrates (vermicompost [V] and coconut fibers [CF] in ratios 20V80CF, 40V60CF, 60V40CF) for four horticultural crop production cycles (PCs) using vermicompost tea (VT) as the main source of nutrients. RESULTS: Readily available water (25%) in the control treatment (20V80CF) was below the recommended limit, and dry bulk density (>450 g/L) surpassed the recommended limit in the 60V40CF treatment (p < 0.05). In terms of chemical properties, cations and anions in the saturated media extract decreased significantly to values below established optimal conditions. Furthermore, the substrates presented high enzymatic activity in successive production cycles (p < 0.05), including dehydrogenase (350-400 µg TFF g-1), acid phosphatase (4,700 µg p-nitrophenol g-1 soil hr-1), and ß-glucosidase (1,200 µg p-nitrophenol g-1 soil hr-1) activity during transformation from organic matter to inorganic compounds. CONCLUSION: The 40V60CF treatment presents adequate physicochemical and biological characteristics for reuse for more than four growing cycles when organic supplements are administered.

Learning to learn in conditioning and extinction in humans.

Learning to Learn (LTL) is the transfer of learning, separate from stimulus generalization, that appears across tasks that share a similar structure. Three experiments examined this phenomenon in both conditioning and extinction learning in humans. The latter effect is of special interest given the failures in the literature to obtain transfer of extinction between stimuli. Conditioning and extinction with one stimulus increased the rate of conditioning and, surprisingly, extinction of a different stimulus (Experiment 1). The effects appeared in the absence of physical generalization. The transfer of extinction was not enhanced by conditions that increased the chances of a mediated extinction effect (Experiment 2). Finally, Experiment 3 ruled out three possible sources for the effect in extinction: a common unconditioned-stimulus representation, a common reinforcement history, and within-stimuli associations. Overall, the findings are consistent with the idea that LTL is an emergent (non-immediate) form of mediated generalization that is dependent upon memory structures retrieved by trial outcomes. The over- or under-prediction of the outcome on the first trial with a new task might retrieve prior episodes associated with similar prediction errors promoting transfer.

Leaching techniques for saline wastes composts used as growing media in organic agriculture: assessment and modelling.

The purpose of this work was to examine solute release by the effect of leaching of a saline compost with two main objectives: (1) to identify the most efficient method for this purpose, in order to minimize the environmental impact of this process in terms of water consumption and (2) to study the composition of the leachates to manage them properly and avoid possible contamination. A laboratory method involving column leaching with distilled water (CL) and two field methods involving saturation leaching (SL) and drip leaching (DL) were compared to this end. In order to more accurately assess nutrient release and compare the three leaching techniques, the cumulative amounts of ions leached were processed by using an exponential growth model. All target ions fitted properly, and so did the curve for the ions as a whole. Salts were removed mainly by effect of the leaching of major ions in the substrate (Na(+), Cl(-), inorganic N, SO4 (2-) and K(+)). SL and CL proved similarly efficient and reduced the salt content of the substrate to an electrical conductivity below 2 dS m(-1) in the saturation extract, which is the optimum level for nursery crops. By contrast, the DL method provided poor results: salt contents were reduced to an electrical conductivity of only 8 dS m(-1) in the saturation extract, so the resulting substrate can only be useful to grow highly salt-tolerant crops.

An easy-to-hard effect after nonreinforced preexposure in a sweetness discrimination.

Experiments 1A and 1B used a taste-aversion procedure with rats to demonstrate that exposure to easily discriminated flavors along a dimension (1 % and 10 % sucrose) can facilitate learning a subsequent hard discrimination (4 % and 7 % sucrose) when one of those flavors is paired with illness. Experiment 1A compared the effects of preexposure to the easily discriminated flavors against exposure to the same stimuli used in the discrimination training or no exposure at all. Experiment 1B replicated the conditions in Experiment 1A, with 2 additional days of training and unrestricted access to the flavors on CS+/CS- trials in discrimination training. Contrary to findings with multidimensional stimuli (Scahill & Mackintosh, Journal of Experimental Psychology: Animal Behavior Processes, 30, 96-103, 2004; Suret & McLaren, The Quarterly Journal of Experimental Psychology, 56B, 30-42, 2003), we found that preexposure to the easily discriminable stimuli varying along a single dimension of sweetness facilitated subsequent discrimination training over the other conditions in each experiment. We discuss the results in terms of the ideas presented by Gibson (1969) and Mackintosh (Psychological Review, 82, 276-298, 1975) and in terms of hedonic variables not considered by theories of perceptual learning.

Presentation and validation of "The Learning Game," a tool to study associative learning in humans.

This article presents a 3-D science-fiction-based videogame method to study learning, and two experiments that we used to validate it. In this method, participants are first trained to respond to enemy spaceships (Stimulus 2, or S2) with particular keypresses, followed by transport to a new context (galaxy), where other manipulations can occur. During conditioning, colored flashing lights (Stimulus 1, or S1) can predict S2, and the response attached to S2 from the prior phase comes to be evoked by S1. In Experiment 1 we demonstrated that, in accord with previous findings from animals, conditioning in this procedure was positively related to the ratio of the time between trials to the time within a trial. Experiment 2 demonstrated the phenomena of extinction, timing, and renewal. Responding to S1 was slightly lost with a context change, and diminished over trials in the absence of S2. On early extinction trials, responding during S1 declined after the time that S2 normally occurred. Extinguished responding to S1 recovered robustly with a context change.

The extinction context enables extinction performance after a change in context.

One experiment with human participants determined the extent to which recovery of extinguished responding with a context switch was due to a failure to retrieve contextually controlled learning, or some other process such as participants learning that context changes signal reversals in the meaning of stimulus-outcome relationships. In a video game, participants learned to suppress mouse clicking in the presence of a stimulus that predicted an attack. Then, that stimulus underwent extinction in a different context (environment within the game). Following extinction, suppression was recovered and then extinguished again during testing in the conditioning context. In a final test, participants that were tested in the context where extinction first took place showed less of a recovery than those tested in a neutral context, but they showed a recovery of suppression nevertheless. A change in context tended to cause a change in the meaning of the stimulus, leading to recovery in both the neutral and extinction contexts. The extinction context attenuated that recovery, perhaps by enabling retrieval of the learning that took place in extinction. Recovery outside an extinction context is due to a failure of the context to enable the learning acquired during extinction, but only in part.

Experimental renewal in human participants.

Two experiments with human participants are presented that differentiate renewal from other behavioral effects that can produce a response after extinction. Participants played a video game and learned to suppress their behavior when sensor stimuli predicted an attack. Contexts (A, B, & C) were provided by fictitious galaxies where the game play took place. In Experiment 1, participants who received conditioning in A, extinction in B, and testing in A showed some context specificity of conditioning during extinction and a recovery of suppression on test. Experiment 2 demonstrated recovery of extinguished responding when participants were conditioned in A, extinguished in B, and tested in C, a third, neutral context. The experiment also demonstrated that the context of extinction did not control performance by becoming inhibitory. Results are discussed in terms of mechanisms that can produce a response recovery after extinction. The experiments demonstrated a renewal effect: a response recovery that was not attributable to the contexts acting as simple conditioned stimuli and is the first work with human participants to conclusively do so.

The contribution of latent inhibition to reduced generalization after pre-exposure to the test stimulus.

Two experiments assessed the contribution of latent inhibition to the generalization-reducing effects of pre-exposure to the test stimulus using a taste aversion procedure in rats. In both experiments, lithium chloride induced illness was paired with a flavor compound (AX) of either salt or sugar (A or B) and hydrochloric acid (X). Generalization of the resulting aversion to a test compound (BX), was assessed after varying pre-exposure to BX, X, and B. Experiment 1 showed that generalization to BX was less when BX itself had been exposed than equivalent pre-exposure to either B and X separately or to B and a new compound (CX). Experiment 2 showed that levels of generalization varied directly as a function of the amount of pre-exposure to BX. The findings show that latent inhibition alone cannot account for the generalization-reducing effect of pre-exposure to BX.