Compensation of neural delays in visual‐motor behaviour: No evidence for shorter afferent delays for visual motion

Abstract

Faces and other objects that share a configuration present a special problem to the visual system. Two components of the visual system's solution to this homogeneity problem have been identified. Inversion studies have identified the use of relational features (Diamond &; Carey, 1986; Rhodes, Brake, &; Atkinson, 1993), and caricature studies have identified norm-based coding (Carey, Rhodes, Diamond, &; Hamilton, in preparation; Rhodes, Brennan, &; Carey, 1987; Rhodes &; McLean, 1990). Here we explore a possible link between these two components, asking whether caricature effects depend selectively on exaggeration of relational features. If so, then inversion, which makes relational features particularly difficult to code (compared with isolated features), should reduce caricature effects. In three experiments we found a caricature equivalence effect (caricatures identified as accurately as undistorted images and both better than anticaricatures) that was unaffected by orientation, suggesting that relational feature coding is not necessary for caricatures to be effective. Therefore, caricature and inversion effects reflect distinct components of face recognition. Caricature level and orientation also interacted differently with other factors, as would be expected if their effects depend upon different underlying processes. For one set of faces there was a caricature advantage in accuracy (Experiments 1 and 3). This superportrait effect occurred even for subjects who were unfamiliar with the faces prior to the experiment (Experiment 3), a result with important forensic implications. Furthermore, the effect was restricted to upright faces. Therefm, although caricatures can be recognized as well as undistorted images whatever features are exaggerated, exaggeration of relational features may be needed for a superportrait effect.     

Contextual cueing in multiple object tracking

In this study, we examined whether visual context can be learned through a dynamic display and whether it can facilitate sustained attentional tracking by combining a multiple object tracking (MOT) task and a contextual cueing procedure. The trajectories of the targets and distractors in the MOT task were made invariant by repeatedly presenting them. The results revealed that when the targets were repeatedly displayed, tracking performance implicitly improved, and this effect was enhanced when the unattended distractors in the displays were also repeated. However, the repetition of the distractors alone did not produce any effect. Interestingly, when the targets and distractors were switched in a display in which the distractors had been previously repeated, the tracking performance was impaired as compared with that in the case of nonrepeated displays. We concluded that the contextual information in a dynamic display facilitates attentional tracking and that different types of contextual modulations occurred in MOT processes, such as facilitation for attended targets and inhibition for ignored distractors.     

Nitric oxide is involved in appetitive but not aversive olfactory learning in the land mollusk Limax valentianus

The land slug Limax performs both aversive and appetitive olfactory learning, and we investigated neurotransmitters involved in each type of learning. Slugs were conditioned by presenting a vegetable juice (appetitive conditioning) or a mixture of vegetable juice and quinidine (aversive conditioning), and the latency to reach the juice became shorter (appetitive conditioning) or longer (aversive conditioning) after conditioning. L-NAME injected either before conditioning or testing blocked the reduction in latency in appetitive conditioning but had no significant effects in aversive conditioning. 5,7-dihydroxytryptamine had no significant effects in appetitive conditioning. These results suggest different mechanisms for appetitive and aversive learning.     

Salivary conditioning with antennal gustatory unconditioned stimulus in an insect

Classical conditioning of olfactory conditioning stimulus (CS) with gustatory unconditioned stimulus (US) in insects has been used as a pertinent model for elucidation of neural mechanisms underlying learning and memory. However, a conditioning system in which stable intracellular recordings from brain neurons are feasibly obtained while monitoring the conditioning effect has remained to be established. Recently, we found classical conditioning of salivation in cockroaches Periplaneta americana, in which an odor was associated with sucrose solution applied to the mouth, and this conditioning could be monitored by activities of salivary neurons. Application of gustatory US to the mouth, however, leads to feeding movement accompanying a movement of the brain that prevents stable recordings from brain neurons. Here we investigated whether a gustatory stimulus presented to an antenna could serve as an effective US for producing salivary conditioning. Presentation of sucrose or sodium chloride solution to an antenna induced salivation and also increased activities of salivary neurons. A single pairing trial of an odor with antennal presentation of sucrose or sodium chloride solution produced conditioning of salivation or of activities of salivary neurons. Five pairing trials led to a conditioning effect that lasted for one day. Water or tactile stimulus presented to an antenna was not effective for producing conditioning. The results demonstrate that gustatory US presented to an antenna is as effective as that presented to the mouth for producing salivary conditioning. This conditioning system provides a useful model for studying the neural basis of learning at the level of singly identifiable neurons.     

Persisting effect of prior experience of change blindness

Most cognitive scientists know that an airplane tends to lose its engine when the display is flickering. How does such prior experience influence visual search? We recorded eye movements made by vision researchers while they were actively performing a change-detection task. In selected trials, we presented Rensink's familiar 'airplane' display, but with changes occurring at locations other than the jet engine. The observers immediately noticed that there was no change in the location where the engine had changed in the previous change-blindness demonstration. Nevertheless, eye-movement analyses indicated that the observers were compelled to look at the location of the unchanged engine. These results demonstrate the powerful effect of prior experience on eye movements, even when the observers are aware of the futility of doing so.     

When sound affects vision: effects of auditory grouping on visual motion perception

Two identical visual targets moving across each other can be perceived either to bounce off or to stream through each other. A brief sound at the moment the targets coincide biases perception toward bouncing. We found that this bounce-inducing effect was attenuated when other identical sounds (auditory flankers) were presented 300 ms before and after the simultaneous sound. The attenuation occurred only when the simultaneous sound and auditory flankers had similar acoustic characteristics and the simultaneous sound was not salient. These results suggest that there is an aspect of auditory-grouping (saliency-assigning) processes that is context-sensitive and can be utilized by the visual system for solving ambiguity. Furthermore, control experiments revealed that such auditory context did not affect the perceptual qualities of the simultaneous sound. Because the attenuation effect is not manifest in the perception of acoustic characteristics of individual sound elements, we conclude that it is a genuine cross-modal effect.     

Pigeons (<Emphasis Type="Italic">Columba livia</Emphasis>) know when they will need hints: prospective metacognition for reference memory?

Despite their impressive cognitive abilities, avian species have shown less evidence for metacognition than mammals. We suspect that commonly used tasks such as matching to sample might be too demanding to allow metacognitive processing within birds’ working memory. Here, we examined whether pigeons could control their behavior as a function of knowledge levels on a three-item sequence learning task, a reference memory task supposedly requiring fewer working memory resources. The experiment used two types of lists differing in familiarity. One was familiar to the pigeons through repeated exposure, whereas the other was novel in every new session. In test sessions, pigeons could choose between a trial with a hint specifying the next item to peck and one with no hint. However, successful responses in trials with a hint resulted in lowered rates of primary reinforcement: .60 in the first test and .75 in the second. Results showed that two of four pigeons chose the trial with a hint significantly more often before receiving a novel list than the familiar list in the four sessions of the first test, and three did so in the second test. Impressively, one bird showed robust evidence in the very first sessions in both tests. These results suggest that pigeons may monitor their long-term knowledge states and thereby control their environment before starting to solve a task.     

Differentiation of international terrorism: attack as threat,means, and violence

This study examined whether international terrorism could be differentiated into different behavioural themes related to the way of using force. The sample consisted of 217 international terrorist organisations that had perpetrated five or more terrorist incidents. A non‐metric multidimensional scaling analysis revealed that all of the terrorist incidents could be assigned to one of three themes reflecting different styles of the use of force: ‘attack as threat’, ‘attack as means’, and ‘attack as violence’. In the current sample, 189 of the terrorist organisations repeated one theme in more than 50% of their series of incidents, suggesting their preference for one of the three themes. Copyright © 2008 John Wiley & Sons, Ltd.