Inhibition of evaluative and perceptual odour–taste learning by attention to the stimulus elements

Pairing of odours and tastes in solution results in the odour taking on the taste's hedonic and perceptual properties. Theoretical accounts of such conditioning propose that the stimulus elements form a configuration with hedonic and/or perceptual properties. One implication of this account is that configural binding may be inhibited by allocation of attention to the individual elements during conditioning (analytical attention). This was tested here by training participants to attend analytically or synthetically during pairing of odours with either sucrose or water. Differential conditioning effects for sucrose- and water-paired odours were seen only in the synthetic group, with sucrose-paired odours increasing in both smelled sweetness and liking. These data support configural models as explanations for these forms of associative learning and emphasize the role of top-down processes in mediating transfer of perceptual and hedonic properties from tastes to odours.     

Losing control in front of a fearful face: The effect of emotional information on cognitive control

How is our cognitive control system modulated by emotional information, especially fearful stimuli? An intuitive hypothesis is that fearful stimuli would enhance cognitive control so that people could switch from the ongoing task to emergent events more quickly to secure themselves. To test this hypothesis, we investigated the influence of emotional information on the shift function of cognitive control by using the task-cueing procedure, in which face images were presented as cues. With the gender of faces indicating which task to do, we manipulated the emotional valence of faces (neutral vs. fearful), finding that the switch costs were larger in the trials containing fearful cues than in the trials containing neutral cues (Experiment 1). This effect was not caused by enlarging task-set interference (Experiment 2), nor by slowing down cue encoding (Experiment 3). Contrary to the intuitive hypothesis, our results suggested that the endogenous task-set reconfiguration process was impaired when fearful faces were presented. We speculated that the benefit of decreasing cognitive flexibility in face of fearful stimuli is to speed up response in a dangerous environment, and this accelerating response is achieved by suppressing the goal-directed system to permit the fast, automatic stimulus-driven system to govern behaviours.     

Aversive conditioning under conditions of restricted awareness: Effects on spatial cueing

In the literature on aversive conditioning there is still debate on the role of awareness. According to some authors, affective learning can occur with or without contingency learning (dual-process model), whereas others argue that a single process produces both affective responses and contingency knowledge. Although many studies have investigated these models, the results to date are inconclusive. Based on a review of the literature, a new series of experiments was designed to examine aversive conditioning in the absence of contingency awareness. In the present study we examined the effects of subliminal aversive conditioning on a spatial cueing task. Awareness was stringently tested after conditioning. Three kinds of awareness were distinguished: contingency awareness (awareness of the CS?US contingencies, where CS is the conditioned stimulus, and US is the unconditioned stimulus), perceptual awareness (awareness of the perceptual differences between the CSs), and US expectancy (awareness of a threat feeling when confronted with the CS+, but not when confronted with the CS?). The results of three experiments demonstrated that responses on the spatial cueing task were modulated by subliminal aversive conditioning. Importantly, none of the participants was contingency aware or able to perceptually discriminate between the conditioned stimuli. However, in Experiment 3, only those participants showing some level of postconditioning expectancy awareness exhibited conditioning effects. These experiments suggest that subliminal aversive conditioning produces small but significant effects, which may be modulated by expectancy awareness.     

The spread of fear: Symbolic generalization mediates graded threat-avoidance in specific phobia

Overgeneralization of fear and threat-avoidance represents a formidable barrier to successful clinical treatment of anxiety disorders. While stimulus generalization along quantifiable physical dimensions has been studied extensively, less consideration has been given to symbolic generalization, in which stimuli are indirectly and arbitrarily related. The present study examined whether the magnitude and extent of symbolic generalization of threat-avoidance and threat-beliefs differed between spider-phobic and nonphobic individuals. Initially, participants learned two sets of stimulus equivalence relations (A1?=?B1?=?C1; A2?=?B2?=?C2). Next, one cue (B1) was established as a conditioned stimulus (CS?+?; threat) that signalled onset of spider images and prompted avoidance, and another cue (B2) was established as a CS– (safety cue) that signalled the absence of such images. Subsequent testing showed that phobics compared to nonphobics exhibited greater symbolic generalization of threat-avoidance to threat cues A1 and C1 (indirect CS+ threat cues related via symmetry and equivalence, respectively), while all individuals showed nonavoidance to indirect safety cues A2 and C2. The enhanced symbolic generalization of threat-beliefs and avoidance behaviour observed in spider phobics warrants further investigation.     

Cholinergic modulation of trace conditioning trained in serial compound: A developmental analysis

In four experiments the effects of serial compound conditioning on responding to a trace-conditioned CS were evaluated using a fear conditioning paradigm. The subjects were 18- and 25-day-old Sprague-Dawley rats, previously shown to exhibit little or no trace fear conditioning. Here, animals as young as 18 days of age were shown to be capable of trace conditioning between a visual CS1 and a shock US, provided the trace interval was filled with a non-target CS2 during serial conditioning trials (CS1-->CS2-->US). To explore cholinergic mechanisms involved in trace and serial conditioning, additional experiments assessed conditioned responding following pre-training administration of the muscarinic receptor antagonist scopolamine. Scopolamine produced a dose-dependent reduction in responding to the trace CS1, regardless of whether subjects were trained with standard trace (CS1-->trace interval-->US) or serial (CS1-->CS2-->US) trials. Responding to CS2 was unaffected by scopolamine. These data suggest that central cholinergic systems are functional in the young animals, but are not normally sufficiently activated by standard trace conditioning procedures. The results suggest that serial compound conditioning can promote trace conditioning in young rats, as it does in adults, perhaps by enhancing cholinergic activity during training. Implications for the late ontogenetic emergence of trace conditioning as it relates to maturation of neural pathways and their role in the potentiating effects of a gap filler are discussed.     

Sex categorization of conspecific pictures in Japanese monkeys (Macaca fuscata)

We investigated whether monkeys discriminate the sex of individuals from their pictures. Whole-body pictures of adult and nonadult monkeys were used as stimuli. Two male Japanese monkeys were trained for a two-choice sex categorization task in which each of two choice pictures were assigned to male and female, respectively. Following the training, the monkeys were presented with novel monkey pictures, and whether they had acquired the categorization task was tested. The results suggested that while monkeys discriminate between the pictures of adult males and females, discrimination of nonadult pictures was difficult. Partial presentations of the pictures showed that conspicuous and sexually characteristic parts (i.e., underbellies including male scrotums or breasts including female nipples) played an important role in the sex categorization.     

The effects of behavioral history on response acquisition with immediate and delayed reinforcement

Effects of prior exposure to the experimental chamber with levers present or absent and variable-time (VT) 60-s water deliveries arranged during one, five, or no 1-hr sessions were examined in rats during a 6-hr response-acquisition session in which presses on one lever produced water delivery immediately or after a 15-s resetting delay, and presses on the other lever canceled scheduled water deliveries. Response acquisition was (a) slower to occur when water deliveries were delayed, (b) most consistent in groups that had received five VT sessions, and (c) impaired by the presence of levers only when there had been five VT sessions and water deliveries were delayed during the acquisition session.     

Medial preoptic area/anterior hypothalamus and sexual motivation

The medial preoptic area/anterior hypothalamus (MPOA/AH) is a brain site derived from proliferative zones from the diencephalon and telencephalon. It is probably this characteristic that makes this brain region participate in different physiological and behavioral functions. The present review addresses the role of the MPOA/AH in the control of male sexual behavior. It is clear that the MPOA/AH is a crucial site in the control of sexual behavior in males of all species studied to date. But although many different publications have followed the contribution of Heimer and Larsson there is no agreement as to what is specifically the role of the MPOA/AH in sexual behavior. At least three hypotheses have been presented. The first one suggests that this brain region is involved in the consummatory aspects (execution) of sexual behavior. The second indicates that the MPOA/AH is involved in the appetitive components (motivation) of masculine sexual behavior. The third hypothesis considers that MPOA/AH neurons are involved in the regulation of consummatory and appetitive aspects of sexual behavior. From the literature reviewed, it will become evident that the evidence supporting a role of the MPOA/AH in the execution of sexual behavior is based on a number of limited studies not easy to interpret. On the other hand, several lines of evidence using a variety of methodologies support the notion that the MPOA/AH is involved in the motivational aspects of male sexual behavior.     

Pavlov And Skinner: Two Lives In Science (An Introduction To B. F. Skinner's "Some Responses To The Stimulus 'Pavlov' ")

The sesquicentennial of Ivan Petrovich Pavlov's birth in September 1999 is being celebrated in Russia by a special issue of the Russian Journal of Physiology (the former I. M. Sechenov Physiological Journal, founded by Pavlov in 1917). The following article and the address by Skinner that it introduces are scheduled to appear in Russian translation in that special issue. Skinner's “Some Responses to the Stimulus ‘Pavlov’” was his presidential address to the Pavlovian Society of North America in 1966. The following article provides the context for Skinner's address by describing some ways in which Pavlov's research influenced Skinner's contributions.     

Olfactory context and memory retrieval in 3-month-old infants

Three experiments examineed whether olfactory stimuli can produce context-dependent effects in infant memory. In eash, 3-month-old infants learned to kick to control the movement of an overhead modile in the presence of an ambient odor. Retention was assessed 1, 3, or 5 days later. During the retention test, the olfactory context was either the same odor, a different odor, or “no odor.” At 1 day, infants exhibited retention when tested in the presence of the same odor. Infants in the no odor condition exhibited partial retention, whereas memory retrieval was completely disrupted for infants tested in the presence of the different odor. After the 3- and 5-day intervals, all groups showed forgetting. These results were not consistent with recent studies of 3-month-old infants trained and tested in the presence of a distinctive visual and auditory context. The findings suggest that olfactory stimuli are a silent feature of the environment for 3-month-old infants, but that they function as context cues in a way that differs from other sensory modalities.