The reference frame for encoding and retention of motion depends on stimulus set size

The goal of this study was to investigate the reference frames used in perceptual encoding and storage of visual motion information. In our experiments, observers viewed multiple moving objects and reported the direction of motion of a randomly selected item. Using a vector-decomposition technique, we computed performance during smooth pursuit with respect to a spatiotopic (nonretinotopic) and to a retinotopic component and compared them with performance during fixation, which served as the baseline. For the stimulus encoding stage, which precedes memory, we found that the reference frame depends on the stimulus set size. For a single moving target, the spatiotopic reference frame had the most significant contribution with some additional contribution from the retinotopic reference frame. When the number of items increased (Set Sizes 3 to 7), the spatiotopic reference frame was able to account for the performance. Finally, when the number of items became larger than 7, the distinction between reference frames vanished. We interpret this finding as a switch to a more abstract nonmetric encoding of motion direction. We found that the retinotopic reference frame was not used in memory. Taken together with other studies, our results suggest that, whereas a retinotopic reference frame may be employed for controlling eye movements, perception and memory use primarily nonretinotopic reference frames. Furthermore, the use of nonretinotopic reference frames appears to be capacity limited. In the case of complex stimuli, the visual system may use perceptual grouping in order to simplify the complexity of stimuli or resort to a nonmetric abstract coding of motion information.     

Judgement bias in pigs is independent of performance in a spatial holeboard task and conditional discrimination learning

Biases in judgement of ambiguous stimuli, as measured in a judgement bias task, have been proposed as a measure of the valence of affective states in animals. We recently suggested a list of criteria for behavioural tests of emotion, one of them stating that responses on the task used to assess emotionality should not be confounded by, among others, differences in learning capacity, i.e. must not simply reflect the cognitive capacity of an animal. We performed three independent studies in which pigs acquired a spatial holeboard task, a free choice maze which simultaneously assesses working memory and reference memory. Next, pigs learned a conditional discrimination between auditory stimuli predicting a large or small reward, a prerequisite for assessment of judgement bias. Once pigs had acquired the conditional discrimination task, optimistic responses to previously unheard ambiguous stimuli were measured in the judgement bias task as choices indicating expectation of the large reward. We found that optimism in the judgement bias task was independent of all three measures of learning and memory indicating that the performance is not dependent on the pig’s cognitive abilities. These results support the use of biases in judgement as proxy indicators of emotional valence in animals.     

The lengthening effect in sequential estimations of a short interval

Summary Experiments were carried out on the lengthening effect in sequential time estimations. It appeared that lengthening only occurred in the case of intuitive evaluation of an interval. Autocorrelation functions revealed that the estimation process may be described as a series of compensatory actions with respect to the last trial. It was assumed that the last estimate is more or less always experienced as too long or too short. In the resulting correction process the positive corrections reach higher mean values than the negative ones since the upper limit of the interval is not defined. In view of the negative autocorrelation in the last trial it was postulated that the correction process is not random, but is related to sequential response bias, i.e. too many alternations. Subsequently, several presentation and estimation modes were compared. The possibility that lengthening might result from trace decay of the standard stored in memory was doubtful since the phenomenon was also observed in the case of pure production on the basis of verbal instructions only. Apparently, it makes no difference whether a standard is presented or not. The distribution of the time estimates under various conditions revealed that the subject becomes more uncertain in proportion as the amount of external reference given increases, so that estimation process variables seem to be of greater importance than stimulus factors (standard presentation). It was assumed that the temporal memory could be described as a register in which only one event (the last) remains available and forms the subject's frame of reference. Since lengthening appeared to be connected with several cognitive variables of a general nature it was postulated that the effect is not only inherent in time estimation, but may be considered as a phenomenon occurring in repeated estimations of various stimuli as well. This assumption appeared to be correct, as analogous effects were observed in the case of repeated line drawing. It was shown that the increase of the time estimates could be influenced significantly by introducing different risk levels, i.e. the degree of lengthening is a function of the subject's decision criterion. Furthermore, there was some correlation between the compensatory actions and sequential response bias in a randomization task. It is concluded that the lengthening effect does not only show a general character, but that it might be described and explained adequately within the framework of the cognitive theory of time experience in which memory mechanisms, decision theory, and sequential response bias play a significant role.     

Coping with threat and memory for ambiguous information: testing the repressive discontinuity hypothesis

Two studies examined the influence of coping dispositions (repression, sensitization, and nondefensiveness) and anxiety on the encoding and memory representation of ambiguous threat-related stimuli. In Study 1, memory was tested shortly after encoding. Study 2 contrasted immediate and delayed testing. Repressers showed evidence of "mixed" affective reactions to ambiguous stimuli at encoding, accompanied by weak memory representation of potentially threatening implications of these stimuli. In contrast, sensitizers and anxious individuals manifested a processing bias in favor of threatening implications of ambiguous stimuli. Influences of coping on memory were most pronounced for delayed testing. Anxiety influences on memory were weak. An expectancy-based account of individual differences in processing ambiguous stimuli is discussed.     

Working memory and spatial judgments: Cognitive load increases the central tendency bias

Previous work demonstrates that memory for simple stimuli can be biased by information about the distribution of which the stimulus is a member. Specifically, people underestimate values greater than the distribution’s average and overestimate values smaller than the average. This is referred to as the central tendency bias. This bias has been explained as an optimal use of both noisy sensory information and category information. In largely separate literature, cognitive load (CL) experiments attempt to manipulate the available working memory of participants in order to observe the effect on choice or judgments. In two experiments, we demonstrate that participants under high cognitive load exhibit a stronger central tendency bias than when under a low cognitive load. Although not anticipated at the outset, we also find that judgments exhibit an anchoring bias not described previously.     

Strategic and perceptual factors producing tilt contrast in dot localization

Encoding spatial location in a frame of reference is often biased by both perceptual and strategic factors. For example,tilt contrast occurs when a line presented in the frame of horizontal and vertical axes appears to be repulsed from the nearest axis, including the diagonal axis of symmetry, due to symmetry perception mechanisms. Research has demonstrated, however, that people can adopt particular viewing strategies that eliminate this effect. In Experiment 1, a similar tilt contrast effect was observed when subjects reproduced from memory the position of a single dot in this reference frame. It was hypothesized that this effect resulted from a combination of strategic and perceptual factors. Specifically, people employ anorigin strategy, coding the location of the dot relative to the origin of the horizontal and vertical axes, thereby establishing a virtual line that appears tilted away from the axes due to the same perceptual processes affecting physically present lines. Two additional experiments support this hypothesis. In Experiment 2, no clear tilt contrast effect was observed in a perception condition, indicating that the tilt effect for dots cannot be accounted for by purely perceptual processes. In Experiment 3, the tilt contrast effect was found to be contingent upon the use of the origin strategy as opposed to a different strategy. The results demonstrate the importance of a viewer's strategy in determining the pattern of distortion observed in spatial encoding.     

Effects of pointing compared with naming and observing during encoding on item and source memory in young and older adults

Research showed that source memory functioning declines with ageing. Evidence suggests that encoding visual stimuli with manual pointing in addition to visual observation can have a positive effect on spatial memory compared with visual observation only. The present study investigated whether pointing at picture locations during encoding would lead to better spatial source memory than naming (Experiment 1) and visual observation only (Experiment 2) in young and older adults. Experiment 3 investigated whether response modality during the test phase would influence spatial source memory performance. Experiments 1 and 2 supported the hypothesis that pointing during encoding led to better source memory for picture locations than naming or observation only. Young adults outperformed older adults on the source memory but not the item memory task in both Experiments 1 and 2. In Experiments 1 and 2, participants manually responded in the test phase. Experiment 3 showed that if participants had to verbally respond in the test phase, the positive effect of pointing compared with naming during encoding disappeared. The results suggest that pointing at picture locations during encoding can enhance spatial source memory in both young and older adults, but only if the response modality is congruent in the test phase.     

空间参照框架的产生机制及与认知机能的关系

空间参照框架是个体表征空间方位的方式, 按照表征中心的不同分为自我中心和环境中心两种参照框架。长期对某一参照框架的持续激活可以形成对该空间参照框架的偏好, 不仅会影响个体的神经元结构, 还会对认知机能产生重要影响。偏好环境中心参照框架会增加海马及其附近脑区的灰质, 而偏好自我中心参照框架会增加尾状核的灰质。海马灰质体积增大会增强正常人的空间记忆能力。持续激活环境中心参照框架的个体会增加海马灰质体积, 从而降低患老年痴呆的风险。未来研究应关注, 地域差异、城乡差异等环境差异在空间参照框架与认知机能关系中的影响机制, 并进一步收集空间参照框架训练在老年痴呆病人中干预效果的实证证据。     

A functionalistic approach to memory: theory and data

The purpose of this article is to propose a conceptual frame of reference for memory research on the basis of two recent lines of development. One such key development is that of a functional orientation of memory research focusing on processing and function rather than structure and memory entities. The other line of development concerns information storage as distributed rather than localized. A functionalistic frame of reference involving a notion of distributed storage is proposed. According to this view remembering is seen as an interaction between available cognitive capabilities and demands of the task in which the individual is remembering something. Encoding is conceived of as an interaction between "affordances" of the environment and "functional dispositions" of the individual. Retrieval is seen as a re-activation of functional dispositions. The formation of unique combinations of functional dispositions plays a crucial role in obtaining perfect recall performance. The viability of the overall conceptual framework is demonstrated in three experimental studies. The development of the design and procedure for these experiments was a second purpose of this paper, namely to outline an experimental setting which could serve as a complement to computer simulations in studying notions of distributed storage.     

Cognitive and neural mechanisms of emotional memory

A highly adaptive aspect of human memory is the enhancement of explicit, consciously accessible memory for emotional stimuli. Recent findings from neuroimaging, neuropsychological, drug and neural stimulation studies indicate that emotional stimuli engage specific cognitive and neural mechanisms that enhance explicit memory. Emotional arousal influences memory via factors that act during memory encoding (attention and elaboration) and factors that modulate memory consolidation. Across studies, the amygdala has been consistently implicated as playing a key role in enhancing explicit memory for both pleasant and unpleasant emotional stimuli through modulation of encoding and consolidation processes.     

Encoding processes in memory scanning tasks

Three experiments are presented that deal with the effect of stimulus probability on the encoding of both alphanumeric characters and nonsense figures. Experiment I replicated a previous finding of an interaction between stimulus probability and stimulus quality in a memory scanning task with numbers as stimuli. Experiments II and III investigated the same paradigm with unfamiliar visual forms as stimuli, and no interaction was found. Results were interpreted as showing that probability affects the encoding mechanism only when the encoding process results in a representation of the name of the stimulus. When stimulus materials are visual forms without names, probability does not appear to affect encoding processes.     

High-fidelity perceptual long-term memory revisited--and confirmed

Experiments on short-term perceptual memory for elemental visual attributes, such as contrast, motion, orientation, and spatial frequency, have relied on a delayed discrimination technique in which the subject compares two stimuli presented at different points in time and memory is indexed by discrimination thresholds measured for the different time intervals between reference and test. In a variant of this procedure, used in experiments on long-term memory, the presentation of a single reference is followed by a memory test that combines two-alternative forced-choice decisions with the method of constant stimuli. With this procedure, it is impossible to distinguish the effects of criterion-setting processes and memory on performance, but this confound can be eliminated by testing many subjects and having each subject make a single decision. The resulting "group thresholds" are stable across time intervals of 24 hr, confirming previous findings of high-fidelity storage in the long-term memory range.     

抑郁症人群的心境一致性认知偏向

心境一致性认知偏向指的是抑郁病人的认知加工偏向负性情绪效价, 简称认知偏向。大量行为学、电生理学以及脑成像学的研究显示该认知偏向主要包括知觉偏向、注意偏向、记忆偏向以及解释偏向。该认知偏向以加工偏向负性、积极偏向缺失以及认知控制受损为特点, 且是杏仁核等边缘系统对负性信息过度激活、纹状体对正性信息激活不足以及额区激活模式异常三个相应脑机制协同作用的产物。目前此领域存在各认知偏向之间联系不清楚、认知偏向和抑郁症的因果关系难以确定以及各研究结果不一致等有待回答的问题, 这些重要问题值得引起该领域未来研究者的注意。     

Category effects on estimates of stimuli: perception or reconstruction?

The present study examined a common category effect that has been reported in the literature: the tendency for estimates of individual stimuli to be biased toward the central value of the presented set of stimuli. Both encoding and reconstruction accounts of this central-tendency effect are considered. Plain vertical lines and vertical lines embedded in the Müller-Lyer illusion were estimated while still in view or from memory. Although bias due to the Müller-Lyer illusion remained constant across the two conditions, bias due to the context set (category) occurred only when stimuli were estimated from memory. The results suggest that the category bias occurs at a later stage of processing that the Müller-Lyer effect and offer support for a reconstruction account of category effects on stimulus estimation.     

Coherence and specificity of information-processing biases in depression and social phobia

Research has not resolved whether depression is associated with a distinct information-processing bias, whether the content of the information-processing bias in depression is specific to themes of loss and sadness, or whether biases are consistent across the tasks most commonly used to assess attention and memory processing. In the present study, participants diagnosed with major depression, social phobia, or no Axis I disorder, completed several information-processing tasks assessing attention and memory for sad, socially threatening, physically threatening, and positive stimuli. As predicted, depressed participants exhibited specific biases for stimuli connoting sadness; social phobic participants did not evidence such specificity for threat stimuli. It is important to note that the different measures of bias in memory and attention were not systematically intercorrelated. Implications for the study of cognitive bias in depression, and for cognitive theory more broadly, are discussed.     

The importance of being upright: Use of environmental and viewer-centered reference frames in shape discriminations of novel three-dimensional objects

We investigated the frame of reference that people use to make shape discriminations when their heads are either upright or tilted. Observers madesame-different judgments of pairs of novel threedimensional objects that were aligned along their length within the frontal-parallel plane and rotated in depth around an axis parallel to their own axes of elongation. The aligned objects were displayed vertically, tilted 45°, or horizontally with respect to the environmental upright, but the distance of each pair from the upright was irrelevant to resolving the angular disparity between the stimuli for thesame-different judgment. Nevertheless, when observers’ heads were upright, the time to encode the stimuli was a linear function of the distance of the stimuli from the environmental upright, whereas when observers’ heads were tilted 45°, encoding times for tilted and vertical stimuli did not differ and were faster than the times to encode horizontal stimuli. We interpreted these data to mean that observers either rotate or reference the top of an object to the environmental upright, and they can use either a gravitational or retinal reference frame to do so when either they or the objects are not upright.     

Cognitive influences on perceptual processing

These experiments investigate the influence of frequency of occurrence of a visual stimulus (stimulus probability) on encoding processes, in an attempt to discover what sorts of mechanisms allow cognitive processes to modify perceptual processes. Experiments 1 and 2 show that frequently occurring visual letters do not facilitate encoding of visually similar letters. This implies that stimulus probability does not directly affect the feature detectors used in encoding the letters. Four more experiments provide evidence that stimulus probability has its effect on the availability of an abstract code that is generated by the encoding process from the visual input. Results from the experiments with letter stimuli could be interpreted using a model similar to the logogen model of Morton. Experiments with nonsense forms suggest that subjects use abstract codes in dealing with the forms only when the stimuli are constructed from a set of orthogonal features. A secondary finding was that visual quality has an effect that extends past the feature analysis stage and into a stage in which the visual input activities an abstract code. This result calls into question the common practice of interpreting the interaction of a factor with visual quality as evidence that the factor affects visual feature analysis.     

Evaluative conditioning depends on higher order encoding processes

Evaluative conditioning (EC) is commonly conceived as stimulus-driven associative learning. Here, we show that internally generated encoding activities mediate EC effects: Neutral conditioned stimuli (CS) faces were paired with positive and negative unconditioned stimuli (US) faces. Depending on the encoding task (Is CS a friend vs. enemy of US?), Experiment 1 yielded either normal EC effects (CS adopting US valence) or a reversal. This pattern was conditional on the degree to which encoding judgements affirmed friend or enemy encoding schemes. Experiments 2a and 2b replicated these findings with more clearly valenced US faces and controlling for demand effects. Experiment 3 demonstrated unconditional encoding effects when participants generated friend or enemy relations between CS and US faces. Explicitly stated friend or enemy relations in Experiment 4 left EC effects unaffected. Together, these findings testify to the importance of higher order cognitive processes in conditioning, much in line with recent evidence on the crucial role of conditioning awareness.