Reinforcing saccadic amplitude variability

Saccadic endpoint variability is often viewed as the outcome of neural noise occurring during sensorimotor processing. However, part of this variability might result from operant learning. We tested this hypothesis by reinforcing dispersions of saccadic amplitude distributions, while maintaining constant their medians. In a first experiment we reinforced the least frequent saccadic amplitudes to increase variability, and then reinforced the central part of the amplitude distributions to reduce variability. The target was placed at a constant distance from the fovea after the saccade to maintain the postsaccadic visual signal constant and an auditory reinforcement was delivered depending on saccadic amplitude. The second experiment tested the effects of the contingency. We reinforced high levels of variability in 4 participants, whereas 4 other participants were assigned to a yoked control group. On average, saccadic amplitude standard deviations were doubled while the medians remained mostly unchanged in the experimental participants in both experiments, and variability returned to baseline level when low variability was reinforced. In the control group no consistent changes in amplitude distributions were observed. These results, showing that variability can be reinforced, challenge the idea of a stochastic neural noise. We instead propose that selection processes constrain saccadic amplitude distributions.     

How emotional pictures influence visuospatial binding in short-term memory in ageing and Alzheimer’s disease?

The present study examines the prediction that emotion can facilitate short-term memory. Nevertheless, emotion also recruits attention to process information, thereby disrupting short-term memory when tasks involve high attentional resources. In this way, we aimed to determine whether there is a differential influence of emotional information on short-term memory in ageing and Alzheimer's disease (AD). Fourteen patients with mild AD, 14 healthy older participants (NC), and 14 younger adults (YA) performed two tasks. In the first task, involving visual short-term memory, participants were asked to remember a picture among four different pictures (negative or neutral) following a brief delay. The second task, a binding memory task, required the recognition by participants of a picture according to its spatial location. The attentional cost involved was higher than for the first task. The pattern of results showed that visual memory performance was better for negative stimuli than for neutral ones, irrespective of the group. In contrast, binding memory performance was essentially poorer for the location of negative pictures in the NC group, and for the location of both negative and neutral stimuli in the AD group, in comparison to the YA group. Taken together, these results show that emotion has beneficial effects on visual short-term memory in ageing and AD. In contrast, emotion does not improve their performances in the binding condition.     

Perspective taking instructions and self-other overlap: Different motives for helping

In two studies (N’s = 57 and 115), we demonstrate that type of perspective-taking instruction (“imagine self” vs. “imagine other”) differentially affects two motives for helping: self-other overlap and empathic concern. Imagine-self instructions produce greater self-other overlap than imagine-target and objective instructions, while both types of perspective-taking instruction promote empathic concern relative to an objective condition. In Study 2, imagine-self instructions indirectly increased the likelihood of helping via empathic concern and self-other overlap, while imagine-target instructions led indirectly to greater helping only through empathic concern. We discuss how different perspective-taking instructions may implicate different emotional and motivational paths to increasing helping.     

Of guns and snakes: testing a modern threat superiority effect*

Previous studies suggest that ancient (i.e. evolutionary-based) threats capture attention because human beings possess an inborn module shaped by evolution and dedicated to their detection. An alternative account proposes that a key feature predicting whether a stimulus will capture attention is its relevance rather than its ontology (i.e. phylogenetic or ontogenetic threat). Within this framework, the present research deals with the attentional capture by threats commonly encountered in our urban environment. In two experiments, we investigate the attentional capture by modern threats (i.e. weapons). In Experiment 1, participants responded to a target preceded by a cue, which was a weapon or a non-threatening stimulus. We found a larger cuing effect (faster reaction times to valid vs. invalid trials) with weapons as compared with non-threatening cues. In Experiment 2, modern (e.g. weapons) and ancient threats (e.g. snakes) were pitted against one another as cues to determine which ones preferentially capture attention. Crucially, participants were faster to detect a target preceded by a modern as opposed to an ancient threat, providing initial evidence for a superiority of modern threat. Overall, the present findings appear more consistent with a relevance-based explanation rather than an evolutionary-based explanation of threat detection.     

Using reinforcement learning to understand the emergence of "intelligent" eye-movement behavior during reading

The eye movements of skilled readers are typically very regular (K. Rayner, 1998). This regularity may arise as a result of the perceptual, cognitive, and motor limitations of the reader (e.g., limited visual acuity) and the inherent constraints of the task (e.g., identifying the words in their correct order). To examine this hypothesis, reinforcement learning was used to allow an artificial "agent" to learn to move its eyes to read as efficiently as possible. The resulting patterns of simulated eye movements resembled those of skilled readers and suggest that important aspects of eye-movement behavior might emerge as a consequence of satisfying the constraints that are imposed on readers. These results also suggest novel interpretations of some contentious empirical results, such as the fixation duration costs associated with word skipping (R. Kliegl & R. Engbert, 2005), and theoretical assumptions, for example the familiarity check in the E-Z Reader model of eye-movement control (E. D. Reichle, A. Pollatsek, D. L. Fisher, & K. Rayner, 1998).     

Cognitive processing specificity of anxious apprehension: impact on distress and performance during speech exposure

The present study examined the impact of different modes of processing anxious apprehension on subsequent anxiety and performance in a stressful speech task. Participants were informed that they would have to give a speech on a difficult topic while being videotaped and evaluated on their performance. They were then randomly assigned to one of three conditions. In a specific processing condition, they were encouraged to explore in detail all the specific aspects (thoughts, emotions, sensations) they experienced while anticipating giving the speech; in a general processing condition, they had to focus on the generic aspects that they would typically experience during anxious anticipation; and in a control, no-processing condition, participants were distracted. Results revealed that at the end of the speech, participants in the specific processing condition reported less anxiety than those in the two other conditions. They were also evaluated by judges to have performed better than those in the control condition, who in turn did better than those in the general processing condition.     

Concurrent Cognitive Processes in Rat Serial Pattern Learning: Item Memory, Serial Position, and Pattern Structure

Three experiments examined the processes mediating rat serial pattern learning for rule-consistent versus rule-violating pattern elements (“violation elements”). In all three experiments, rats were trained to press retractable levers in a circular array in a specific sequence for brain-stimulation reward (BSR). Experiment 1 examined the role of lever location (L) and element serial position (SP) cues in rats’ ability to learn to anticipate a violation element positioned at the end of a 24-element serial pattern. Rats with L cues either alone or in combination with SP cues learned to anticipate the violation element, whereas those with SP cues alone did not. Rats in groups L and L + SP underwent a series of transfers designed to remove various cues that might have controlled their performance on the violation element. Results indicated that intra-chamber lever location cues mediated performance on the violation element whereas performance on rule-consistent elements within pattern chunks was mediated by an internal mnemonic representation that was insensitive to changes in lever location cues. Experiment 2 examined whether rats could learn to use SP cues alone to anticipate a violation element if it was positioned earlier in a serial pattern. Rats learned to anticipate the violation element based on SP cues alone when it was located in SP6 in a 24-element pattern, but not when it was in SP12. Experiment 3 examined whether or not rats spontaneously encode information about chunk length and the serial position of phrasing cues in serial patterns. Rats were trained to a high criterion on the serial pattern used in Experiment 1, then were challenged with three probe patterns that manipulated both chunk length and overall pattern length. Results indicated that rats spontaneously encoded information regarding the serial position of phrasing cues in relation to chunk length. Thus, rats appear to use at least three cognitive processes concurrently in serial pattern learning tasks, namely, item memory involving external discriminative cues, counting- or timing-like processes for encoding serial position, and rule abstraction for encoding an internal representation of pattern structure.