Analysis of a trial-spacing effect with relatively long intertrial intervals

In three experiments with rat subjects, we examined the effects of trial spacing in appetitive conditioning. Previous research in this preparation suggests that self-generated priming of the conditional stimulus (CS) and/or unconditional stimulus (US) in short-term memory is a cause of the trial-spacing effect that occurs with intertrial intervals (ITIs) of less than 240 sec. Experiment 1 nonetheless showed that a trial-spacing effect still occurs when ITIs are increased beyond 240 sec, and that the effect of ITI over 60–1,920 sec on conditioned responding is best described as a linear function. In Experiment 2, some subjects were removed from the context during the ITIs, preventing extinction of the context. Removal abolished the advantage of the long ITI, suggesting the importance of exposure to the context during the long ITI. Experiment 3 still produced a trial-spacing effect in a within-subjects design that controlled for the level of context conditioning and reinforcement rate in the absence of the CS. Overall, the results are most consistent with the idea that adding time to the ITI above 240 sec facilitates conditioning by extinguishing context-CS associations—and possibly context-US associations—that otherwise interfere with CS-US learning through retrieval-generated priming (see, e.g., Wagner, 1981).     

Overshadowing of environmental cues by an odor in toxicosis-based conditioning in rats

It was demonstrated that an odor presented to rats in a distinctive environment can interfere with toxicosis-based conditioning to the environmental cues. Rats poisoned when they drank unflavored water in a black compartment odorized with oil of eucalyptus exhibited no suppression of water intake when they were subsequently tested in the same compartment minus the odor. In contrast, rats poisoned in the same compartment minus the odor later exhibited reduced water consumption in that environment. Oil of eucalyptus proved to be as effective an overshadowing stimulus as a taste cue (a 1.5% NaCl solution).     

Overshadowing of geometric cues by a beacon in a spatial navigation task

In three experiments, we examined whether overshadowing of geometric cues by a discrete landmark (beacon) is due to the relative saliences of the cues. Using a virtual water maze task, human participants were required to locate a platform marked by a beacon in a distinctively shaped pool. In Experiment 1, the beacon overshadowed geometric cues in a trapezium, but not in an isosceles triangle. The longer escape latencies during acquisition in the trapezium control group with no beacon suggest that the geometric cues in the trapezium were less salient than those in the triangle. In Experiment 2, we evaluated whether generalization decrement, caused by the removal of the beacon at test, could account for overshadowing. An additional beacon was placed in an alternative corner. For the control groups, the beacons were identical; for the overshadow groups, they were visually unique. Overshadowing was again found in the trapezium. In Experiment 3, we tested whether the absence of overshadowing in the triangle was due to the geometric cues being more salient than the beacon. Following training, the beacon was relocated to a different corner. Participants approached the beacon rather than the trained platform corner, suggesting that the beacon was more salient. These results suggest that associative processes do not fully explain cue competition in the spatial domain.     

Children's integration of facial and situational cues to emotion

Children at 4 age levels (3-5, 6-7, 8-9, and 10-12 years) were shown a series of pictures in which facial and situational cues were (a) congruent, (b) conflicting, or (c) presented alone. Children rated the type (happy or sad) and intensity of the emotion felt by each character. Developmental changes in the relative weights assigned to facial and situational cues were examined using Anderson's information integration approach. The results showed that children's reliance on situational cues increased with age, but their reliance on facial expression decreased with age. Analysis of individual children's ratings indicated a developmental increase in the tendency to integrate facial and situational cues. Children's ability to resolve the conflicting cues (through stories) also increased with age, but there were no age differences in the types of resolutions used. At all age levels, children were less likely to resolve pictures involving an inconsistent positive expression than pictures showing an inconsistent negative expression.     

The effects of intertrial and feature-target intervals on operant serial feature-positive discrimination learning

The effects of intertrial interval (ITI) and feature-target interval (FTI) on the nature of learning in discrete-trial operant serial feature-positive (feature → target+ / target?) discrimination training were examined in two experiments with rats. Discrimination performance was acquired more rapidly with longer ITIs and shorter FTIs. In contrast, transfer to a separately trained target was greater with shorter ITIs regardless of FTI. Persistence of discrimination performance after feature extinction was greater with longer ITIs. Only the last of these performance measures showed evidence for invariance with constant ITI/FTI ratios. The results are discussed in the context of theories of occasion setting.     

Overshadowing not potentiation of illness-based contextual conditioning by a novel taste

In four experiments using rat subjects, we investigated the effects of presenting a novel flavor cue at the time of pairing an environmental context with illness. In each experiment, the subjects were allowed to spend time in a distinctive cage before receiving an injection of LiCl. For some, plain water was made available on these conditioning trials; for others, a novel taste (HCl) was presented. We measured the strength of the context aversion by assessing the ability of the contextual cues to block the acquisition of an aversion to sucrose in a further phase of training. We found that initial training with HCl present made the context less effective as a blocking cue and concluded that the HCl had overshadowed learning about the context. We suggest that this blocking procedure provides a more accurate assessment of contextual aversion than does the consumption test that has more usually been used and that taste-context overshadowing may be a more robust phenomenon than has thus far been thought.     

Influence of intertrial interval duration on the intertrial agreement effect in delayed matching-to-sample with pigeons

Accuracy on even-numbered trials was assessed as a function of (1) the relation between the sample on the immediately preceding trial and that on the current trial and (2) the length of the intertrial interval (ITI) that intervened between odd- and even-numbered trials. A relatively long interval intervened between pairs of trials in the clustered-dyads procedure, whereas this interval was equal to the ITI in the massed-trials procedure. Both procedures revealed an intertrial agreement effect in that accuracy was higher when the sample on the immediately preceding trial was identical rather than opposite. A decrease in the magnitude of this effect at longer ITIs was apparent only in the clustered-dyads procedure. The insensitivity of the intertrial agreement effect to variations in ITI in the massed-trials procedure may reflect floor effects and the carryover of memory from multiple prior trials that mask the true magnitude of the intertrial agreement effect at short ITIs.     

Extended exposure to environmental cues,but not to sucrose,reduces sucrose cue reactivity in rats

In the present study, we examined the effects of extinction of sucrose-predictive contextual cues and/or sucrose satiation on the expression of sucrose cue reactivity in a rat model of relapse. Context extinction was imposed by housing rats in their home cage or in the operant conditioning chamber for 17 h prior to testing. For sucrose satiation, rats were allowed unlimited access to water or sucrose for 17 h prior to testing. Cue reactivity was assessed after either one (Day 1) or 30 (Day 30) days of forced abstinence from sucrose self-administration. An abstinence-dependent increase in sucrose cue reactivity was observed in all conditions (“incubation of craving”). Context extinction dramatically reduced lever responding on both Day 1 and Day 30. Sucrose satiation had no significant effect on cue reactivity in any condition. These results demonstrate that the context in which self-administration occurs maintains a powerful influence over cue reactivity, even after extended forced abstinence. In contrast, the primary reinforcer has little control over cue reactivity. These findings highlight the important role of conditioned contextual cues in driving relapse behavior.     

《素问》"生而勿杀、予而勿夺、赏而勿罚"语义辨析

《素问·四气调神大论》是古代医家在“天人相应”观指导下,根据四季气候变化对人体的影响,提出如何顺应四时阴阳变化规律而养生防病的一篇极为重要的文献。正确地译释该文,对继承、发掘前人的学术思想,拓展与丰富养生保健的方法与措施十分重要。但对原文中“生而勿杀、予而勿夺、赏而勿罚”句的语义,自唐、明、清代至今,历代注家见解不一。或言其意指应“顺时待物”;或言其意为“勿伐天时”;或言其意是指人不同的“神志活动”;或言其意仅为春生之气的“形容词”等等。本文从原文的主旨、语言逻辑、语法规律、词义注释、中医理论等方面提出了自己全新的看法。认为“生、予、赏”三句是古人对如何顺应春生之气养生防病的具体要求;并由此提出春季养生防病应重在调肝护肝和顺时序治疗肝病的新观点。     

Stimuli associated with the cancellation of food and its cues enhance eating but display negative incentive value

Initially neutral conditioned stimuli paired with food often acquire motivating properties, including serving as secondary reinforcers, enhancing instrumental responding in Pavlovian-instrumental transfer procedures, and potentiating food consumption under conditions of food satiation. Interestingly, cues associated with the cancellation of food and food cues may also potentiate food consumption (e.g., Galarce and Holland, 2009), despite their apparent negative correlations with food delivery. In three experiments with rats, we investigated conditions under which potentiation of feeding by such “interruption stimuIi” (ISs) develops, and some aspects of the content of that learning. Although in all three experiments ISs enhanced food consumption beyond control levels, they were found to act as conditioned inhibitors for anticipatory food cup entry (Experiment 1), to serve as conditioned punishers of instrumental responding (Experiment 2), and to suppress instrumental lever press responding in a Pavlovian instrumental transfer procedure (Experiment 3). Furthermore, when given concurrent choice between different foods, an IS enhanced consumption of the food whose interruption it had previously signaled, but when given a choice between performing two instrumental responses, the IS shifted rats’ choice away from the response that had previously yielded the food whose interruption had been signaled by IS (Experiment 3). Thus, the effects of an IS on appetitive responses were opposite to its effects on consummatory responding. Implications for our understanding of learned incentive motivation and the control of overeating are discussed.     

Beyond situational ambiguity in peer conflict: unique and combined effects of cues from an antagonist and a best friend

In accord with increasing recognition of the situation specificity of childhood social behaviors, individual and contextual differences in children's responses to potential peer conflict were examined (hostile attribution, behavioral strategies, and affective reactions; N = 367, 9-12 years, 197 girls). Situational cues from 2 sources, the antagonist and a witnessing best friend, were designed to suggest the antagonist's intentions. Multilevel modeling indicated that children's responses generally varied more according to cues from the antagonist than friend, but the latter also affected responses, especially when conflicting with other situational information. Cognitive and affective responses were also influenced by gender, social goals, friendship quality, and self-efficacy for peer interaction. Findings provide theoretical insight on the context of peer conflict.     

Retrieval practice after multiple context changes,but not long retention intervals,reduces the impact of a final context change on instrumental behavior

Recent evidence from this laboratory suggests that a context switch after operant learning consistently results in a decrement in responding. One way to reduce this decrement is to train the response in multiple contexts. One interpretation of this result, rooted in stimulus sampling theory, is that conditioning of a greater number of common stimulus elements arising from more contexts causes better generalization to new contexts. An alternative explanation is that each change of context causes more effortful retrieval, and practice involving effortful retrieval results in learning that is better able to transfer to new situations. The current experiments were designed to differentiate between these two explanations for the first time in an animal learning and memory task. Experiment 1 demonstrated that the detrimental impact of a context change on an instrumental nose-poking response can be reduced by training the response in multiple contexts. Experiment 2 then found that a training procedure which inserted extended retention intervals between successive training sessions did not reduce the detrimental impact of a final context change. This occurred even though the inserted retention intervals had a detrimental impact on responding (and, thus, presumably retrieval) similar to the effect that context switches had in Experiment 1. Together, the results suggest that effortful retrieval practice may not be sufficient to reduce the negative impact of a context change on instrumental behavior. A common elements explanation which supposes that physical and temporal contextual cues do not overlap may account for the findings more readily.     

Outcome-selective effects of intertrial reinforcement in a Pavlovian appetitive conditioning paradigm with rats

The outcome-selective effects of presenting intertrial unconditioned stimuli (USs) in a rat appetitive conditioning paradigm were examined in two experiments. In both experiments, two stimuli were paired with different outcomes, while one of these outcomes was also presented in the intertrial interval (A+, B*, +). Two measures of learning, stimulus-elicited magazine approach and Pavlovian-to-instrumental transfer, were used to examine these effects. The presence of freely occurring outcomes in the intertrial interval (ITI) was observed to interfere more with the learning of a new association (Experiment 1) and to degrade more an already established association (Experiment 2) when the conditioned stimulus had been paired with the same outcome as that occurring in the ITI. An outcome-selective effect of ITI USs distinguishes among accounts of contingency based on general performance, attentional, and motivational mechanisms from those based on more specific associative mechanisms. Overall, the data highlight the importance of specific encoding processes in the analysis of associative learning.     

To cheat or not to cheat: effects of moral perspective and situational variables on students' attitudes

One hundred and ninety‐six Israeli middle‐school students participated in a study that explored the effects of moral orientation (moral versus conventional)and of three situational variables on attitudes toward two types of cheating in school exams—copying from others (‘active’)and letting others copy (‘passive’). Several vignettes that were comprised of different combinations of the three situational variables—exam importance, supervision level and peers' norms—were used as the main instrument. It was found that a‐morally oriented students approved significantly more of cheating than morally oriented students. Importance of exam had marginally significant effects on active copying. Level of supervision during exam and classmates' norms had significant effects on both active and passive cheating attitudes.     

Under threat but engaged: Stereotype threat leads women to engage with female but not male partners in math

This research tests how experiencing stereotype threat before a dyadic interaction affects women’s engagement with peers during a dyadic math task. In a pilot study (N = 167; M_age = 20.1 years), women who completed a manipulation of stereotype threat (a socially evaluative math task in front of male evaluators) experienced greater subjective threat than did men. In Studies 1A and 1B, math-identified female undergraduates completed the stereotype threat or control (doing math alone) manipulation and then completed a collaborative math task with another female or male student (who completed the control task). Sympathetic nervous system responses were collected to measure physiological linkage—the effect of participants’ physiological states on their partners’ subsequent physiological states—as an indicator of attention to the partner. We also measured the number of math-related questions participants asked their partners and task performance. In Study 1A (female-female dyads; N = 104; M_age = 19.9 years), threatened women asked more questions than controls did and became physiologically linked to their partners when those partners were speaking about math. Threatened women performed comparably to controls. In Study 1B (female-male dyads; N = 140; M_age = 20.0 years), threatened women did not ask more questions of their male partners than controls did, nor did they show physiological linkage to their male partners. Women performed worse than men did, regardless of condition. When working with a female, experiencing stereotype threat outside of a working interaction leads women to engage more; this effect does not occur when with a male.     

The effects of changeover delays of fixed or variable duration on concurrent variable-interval performance in pigeons

The effects of changeover delays of fixed or variable duration on concurrent variable-interval performance in pigeons were investigated in a series of three experiments. Experiment 1 compared the effects of a fixed, variable, or variable signaled changeover delay on interchangeover times and responding during and after the changeover delay. The duration of the changeover delays was systematically varied in Experiment 2, and the relative reinforcement frequencies were manipulated in Experiment 3. Interchangeover times were found to be shorter when changeover delays of variable duration were compared with those of fixed duration. Changeover delays of fixed duration produced higher response rates during the changeover delay than after the changeover delay had elapsed; changeover delays of variable duration produced such differences to a lesser extent. It was concluded that the changeover delay in concurrent variable-interval schedules of reinforcement functionally acts as a delay period to the next opportunity for reinforcement, possibly serving as a conditioned reinforcer for the behavior preceding it (the interchangeover time) and as a discriminative stimulus for the behavior in its presence (response rates during the delay).     

Apparent disinhibition of successive but not of simultaneous negative contrast

In a series of three experiments, rats shifted from a 32% to a 4% sucrose solution, after 10 days’ exposure to the 32% solution, exhibited a negative contrast effect in lick rate. In each experiment, shifted rats that received a novel stimulus (tone) during the postshift period exhibited a higher lick rate (smaller contrast effect) than shifted subjects not receiving the tone. This increase in lick rate resembles Pavlovian disinhibition and is interpreted as supporting an inhibitory view of successive negative contrast effects. Control conditions included in Experiments 2 and 3 favored the disinhibition interpretation of the effect of the tone, as opposed to a rate-dependency hypothesis or to the nonspecific energization of behavior. In Experiments 4–6, the tone was introduced coincident with the occurrence of a simultaneous negative contrast effect. Rather than disinhibition, a decrease in licking occurred. These results were discussed in terms of differences between successive and simultaneous contrast.     

An eye tracking comparison of external pointing cues and internal continuous cues in learning with complex animations

Two experiments used eye tracking to investigate a novel cueing approach for directing learner attention to low salience, high relevance aspects of a complex animation. In the first experiment, comprehension of a piano mechanism animation containing spreading-colour cues was compared with comprehension obtained with arrow cues or no cues. Eye tracking data revealed differences in learner attention patterns between the different experimental conditions. The second experiment used eye tracking with synchronized and non-synchronized cues to investigate the role of dynamic direction of attention in cueing effectiveness. Results of Experiment 1 showed that spreading-colour cues resulted in better targeting of attention to thematically relevant aspects and in higher comprehension scores than arrow cues or no cues. For Experiment 2, superior comprehension after the synchronized version together with eye tracking data indicated that cue effectiveness depended on attention direction being spatially and temporally coordinated with onsets of animation events having high thematic relevance to the learning task. The findings suggest the importance of perceptual cues and bottom-up processing.     

Stimulus- and feeder-directed behavior in a long-box: Effect of fixed versus variable time schedules of food presentation

Two groups of 6 pigeons were exposed to either a fixed-time (FT) or a variable-time (VT) schedule of response-independent food presentation. The interval between two successive food presentations (food-food [FF] interval) was either 20 or 40 sec. The duration of stimulus presentation (stimulus-food [SF] interval) was varied relative to the FF interval. All subjects were exposed to different information ratios (IRs; IR = SF/FF; IR = 1.00, 0.50, 0.15). To study the relative contribution of sign- and goal-tracking behavior to keypecking observed in standard autoshaping procedures, pigeons were autoshaped in a long-box. In the long-box, the stimulus key and the feeder are located 60 cm apart. Stimuli were always presented at one end of the box, and food was presented at the other end. Locomotor behavior and keypecks were recorded. Pigeons engaged in sign-tracking behavior when IR = 0.15, but only when presentation of the food was unpredictable on the basis of other variables (e.g., the passage of time since the last food presentation, as in FT schedules). In the case of FT schedules, subjects engaged in feeder-directed activities. No effects of varying the FF interval were found. Keypecking was observed only when the SF interval was short (IR = 0.15) and food was presented on a VT schedule.     

Interocular transfer of simultaneous but not successive discriminations in the pigeon

Pigeons were trained with one eye covered on each of two types of visual discriminations. They then were tested for interocular transfer with the previously covered eye. Transfer was shown by every pigeon trained on a simultaneous discrimination, while lack of transfer was shown by thesesame pigeons when trained on a spatial conditional (successive) discrimination. As opposed to the pigeon, animals with a larger proportion of ipsilateral (uncrossed) retinal fibers (e.g., cats) do show transfer of both discrimination problems. This difference in the decussation of the optic pathways may be a critical variable in interocular transfer in vertebrates. Furthermore, these studies demonstrate that interocular transfer in the pigeon depends upon the experimental paradigm.