The resistance of renewal to instructions that devalue the role of contextual cues in a conditioned suppression task with humans

The renewal of extinguished conditioned behaviour appears to reflect context-dependent learning. The present research used a conditioned suppression task with humans to examine whether instructions concerning the context could influence renewal. Pairings of a conditional stimulus (CS) and unconditional stimulus (US) were made in one context, followed by extinction trials of CS alone in a second context, and test trials of CS alone upon return to the original learning context. Four experiments tested whether the renewal of conditioned suppression observed during test would be attenuated if participants were instructed that the context changes were irrelevant to the predictive relationship between the CS and US. Using a differential conditioning design, no attenuation was found when the instructions were given prior to conditioning (Experiment 1) or immediately prior to the test trials (Experiment 2). The latter result was replicated with a single-cue conditioning design and further controls for exposure to the extinction contexts (Experiment 3). The collection of on-line ratings about the relationship between the contextual changes and the predictive nature of the CS indicated that participants did attend to and believe the instructions (Experiment 4). The results point to the resistance of renewal to explicit instructions that attempt to devalue the role of the contextual cues.     

Of snakes and faces: An evolutionary perspective on the psychology of fear

Snakes and faces are unique stimuli because they are deeply grounded in evolutionarily shaped behavior systems. Snakes are the prototypical stimulus in a predatory defense system promoting escape from predators, which prepares primates for efficient processing, attentional priority, and rapid fear acquisition to snakes and other stimuli related to predation. The social submissiveness system plays a similar role on the social arena by promoting yielding to dominant individuals without jeopardizing the protection of the group. Supporting these theoretical propositions, empirical data from a research program spanning four decades demonstrate enhanced fear conditioning to snakes and threatening faces compared to neutral stimuli, as well as fast nonconscious processing of, and prioritized attention to, snakes and threatening faces. Human brain‐imaging data show that these effects are mediated by an extensive fear‐network centering on the amygdala.     

Context blocking in rat autoshaping: Sign-tracking versus goal-tracking

Prior experience of unsignaled food can interfere with subsequent acquisition by birds of autoshaped key-pecking at a signal light. This has been understood to indicate that unsignaled food results in context conditioning, which blocks subsequent learning about the keylight-food relationship. In the present experiment with rats lever insertion as the conditioned stimulus (CS) preceded sucrose delivery as the unconditioned stimulus (US). Half the rats initially received unsignaled USs in the conditioning context, while the remainder did not. Both lever-presses (sign-tracking) and magazine-entries (goal-tracking) were recorded. Under immediate reinforcement conditions, prior unsignaled US interfered with sign-tracking, but had no effect on goal-tracking. In two further groups, a trace condition prevented development of sign-tracking. In this case, prior context conditioning interfered with goal-tracking. These results suggest that interference with sign-tracking may reflect response competition, while interference with goal-tracking under trace conditions may reflect failure to acquire a CS-US association.     

Changing explicit and implicit attitudes: The case of self-esteem

Three experiments investigated predictions concerning asymmetrical patterns of implicit and explicit self-esteem change. Specifically, we investigated the influence of knowledge about the own self that is momentarily salient as well as the influence of affective valence associated with the self in memory on implicit and explicit self-esteem. The latter was induced by evaluative conditioning, the former by directed thinking about oneself. We found that while evaluative conditioning changed implicit but not explicit self-esteem (Experiment 1), thinking about the own self altered explicit but not implicit self-esteem (Experiment 2). Moreover, in a third experiment, it could be shown that the effect of evaluative conditioning can spill over to the explicit level when participants are asked to focus on their feelings prior to making their self-report judgements (Experiment 3). Implications of our results are discussed in terms of recent controversies regarding dual-process models of attitudes and associative versus propositional modes of information processing.     

Acute systemic fibroblast growth factor-2 enhances long-term memory in developing rats

Recent findings have provided much insight into the mechanisms underlying long-term memory formation, and it is now known that long-term memory depends on the activation of a molecular cascade that culminates with structural changes in the brain. However, little is known about the signals that give rise to or regulate these structural changes. In this article we propose that fibroblast growth factor-2 (FGF2), a mitogen for several cell types, may be one of the molecular signals critically involved in the structural changes underlying long-term memory. If FGF2 is part of the signalling cascade involved in long-term memory, then increasing the activation of FGF2 should facilitate memory. In Experiments 1 and 2, we demonstrated that systemic injection of FGF2 (20 ng/g of body weight) facilitated memory for contextual fear in 16, 19, and 22 day old male Sprague Dawley rats. Experiment 3 demonstrated that the observed facilitation of memory was not due to FGF2 increasing rats’ sensitivity to footshock. These results implicate FGF2 as a possible molecular signal in long-term memory, and further, illustrate a novel means of enhancing memory.     

Sensitization and habituation regulate reinforcer effectiveness

We argue that sensitization and habituation occur to the sensory properties of reinforcers when those reinforcers are presented repeatedly or for a prolonged time. Sensitization increases, and habituation decreases, the ability of a reinforcer to control behavior. Supporting this argument, the rate of operant responding changes systematically within experimental sessions even when the programmed rate of reinforcement is held constant across the session. These within-session changes in operant responding are produced by repeated delivery of the reinforcer, and their empirical characteristics correspond to the characteristics of behavior undergoing sensitization and habituation. Two characteristics of habituation (dishabituation, stimulus specificity) are particularly useful in separating habituation from alternative explanations. Arguing that habituation occurs to reinforcers expands the domain of habituation. The argument implies that habituation occurs to biologically important, not just to neutral, stimuli. The argument also implies that habituation may be observed in “voluntary” (operant), not just in reflexive, behavior. Expanding the domain of habituation has important implications for understanding operant and classical conditioning. Habituation may also contribute to the regulation of motivated behaviors. Habituation provides a more accurate and a less cumbersome explanation for motivated behaviors than homeostasis. Habituation also has some surprising, and easily testable, implications for the control of motivated behaviors.     

情绪记忆的神经基础

情绪记忆具有强烈、持久的特点,在记忆中具有优势地位。杏仁核是情绪记忆的关键脑区,其外侧核被认为是情绪回路建立的中心部位。恐惧条件反射是情绪记忆,特别是情绪回路研究的有效手段。情绪记忆的编码,储存与提取受到杏仁核与各相关脑区共同影响,其中激素调节在这些过程中发挥重要作用。文中结合最新的研究成果对情绪记忆的神经机制进行讨论     

The kinematics of belief and desire

Richard Jeffrey regarded the version of Bayesian decision theory he floated in ‘The Logic of Decision’ and the idea of a probability kinematics—a generalisation of Bayesian conditioning to contexts in which the evidence is ‘uncertain’—as his two most important contributions to philosophy. This paper aims to connect them by developing kinematical models for the study of preference change and practical deliberation. Preference change is treated in a manner analogous to Jeffrey’s handling of belief change: not as mechanical outputs of combinations of intrinsic desires plus information, but as a matter of judgement and of making up one’s mind. In the first section Jeffrey’s probability kinematics is motivated and extended to the treatment of changes in conditional belief. In the second, analogous kinematical models are developed for preference change and in particular belief-induced change that depends on an invariance condition for conditional preference. The two are the brought together in the last section in a tentative model of pratical deliberation. This paper is one of a pair dedicated to Richard Jeffrey and prepared for a workshop held in his memory at the 26th International Wittgenstein Symposium. My thanks to the organisers of, and the participants in, this workshop and to two anonymous referees for their comments.     

Net Amount of Food Affects Autoshaped Response Rate, Response Latency, and Gape Amplitude in Pigeons

The contribution of net amount of food to conditioned response strength and topography was assessed in four pigeons under autoshaping contingencies. In each session, under one baseline phase and three replication phases, three trial types were presented sequentially: One conditioned stimulus (keylight) signaled one small pellet, another signaled one large pellet, and a third signaled seven small pellets which were weight-matched to one large pellet. Five dependent variables were response rates and latencies based on the occurrence of both keyswitch closures and gapes (beak openings) and gape amplitudes. In result, net amount of food, not pellet diameter or number, affected all dependent variables. Notably, gape amplitudes elicited by the seven-small pellet keylights were larger than the gape amplutides elicited by the one-small pellet keylights even though the gape amplitudes elicited by both unconditioned stimuli (one or seven pellets) were equally small. This mismatch between conditioned and unconditioned responses is incompatible with stimulus substitution accounts but is compatible with an associative strength account. Furthermore, the changes in the dependent variables were most likely determined by Pavlovian and not by inadvertent operant contingencies. The findings demonstrate that an analysis of classical conditioning benefits from the inclusion of topographical measures.     

Psychoneuroimmunology

Psychoneuroimmunology is the study of the relationships among behavioral, neural and endocrine, and immune processes. Bidirectional pathways connect the brain and the immune system and provide the foundation for neural, endocrine, and behavioral effects on immunity. Examples of such effects are conditioned and stress-induced changes in immune function and in susceptibility to immunologically mediated diseases. These data indicate that researchers should no longer study the immune system as if it functioned independently of other systems in the body. Changes in immune function are hypothesized to mediate the effects of psychological factors on the development of some diseases, and research strategies for studying the clinical significance of behaviorally induced changes in immune function are suggested.