The impact of orienting attention in fast task-irrelevant perceptual learning

Task-irrelevant perceptual learning (TIPL) refers to the phenomenon where the stimulus features are learned when they are consistently presented at behaviorally relevant times (e.g., with task targets or rewards). Studies on the role of attention in TIPL have found that attention negatively impacts this type of learning; however, these studies involved stimuli that were completely irrelevant to the subjects and that, when noticed, were distracting to the subjects?? task. Here, we asked whether attention would have a beneficial impact on learning in the case where the target-paired stimuli were relevant to a secondary task that subjects were required to perform. We conducted three experiments in adult subjects, using the fast-TIPL paradigm (which allows one to study TIPL with as little as a single trial of exposure). The results from Experiments 1 and 2 showed that fast-TIPL occurred for the target-paired stimuli but that the manipulation of attention increased performance for stimuli presented after the target. Experiment 3 was conducted to address whether the direction of attention positively or negatively impacted fast-TIPL and to better control for the effects of attention. The results of this experiment demonstrate that in the case of fast-TIPL, exogenously directed attention aids in the memorization of target-paired stimuli. Overall, our results demonstrate that attention operates in a beneficial manner in fast-TIPL, where the target-paired stimuli are relevant to a secondary task that subjects perform.     

Unconsciously learning task-irrelevant perceptual sequences

We demonstrated unconscious learning of task-irrelevant perceptual regularities in a Serial Reaction Time (SRT) task in both visual and auditory domains. Participants were required to respond to different letters (‘F’ or ‘J’, experiment 1) or syllables (‘can’ or ‘you’, experiment 2) which occurred in random order. Unbeknownst to participants, the color (red, green, blue or yellow) of the two letters or the tone (1–4) of the syllables varied according to certain rules. Reaction times indicated that people indeed learnt both the color and tonal regularities indicating that task-irrelevant sequence structure can be learned perceptually. In a subsequent prediction test of knowledge of the color or tonal cues using subjective measures, we showed that people could acquire task irrelevant knowledge unconsciously.     

Linguistic cues enhance the learning of perceptual cues

When language is correlated with regularities in the world, does it enhance the learning of these regularities? This question lies at the core of both notions of linguistic bootstrapping in children and the Whorfian hypothesis. Support for an affirmative answer is provided in an artificial-noun-learning task in which 2-year-old children were taught to distinguish categories of solid and nonsolid things with and without supporting correlated linguistic cues.     

Multisensory perceptual learning reshapes both fast and slow mechanisms of crossmodal processing

Previous research has shown that sounds facilitate perception of visual patterns appearing immediately after the sound but impair perception of patterns appearing after some delay. Here we examined the spatial gradient of the fast crossmodal facilitation effect and the slow inhibition effect in order to test whether they reflect separate mechanisms. We found that crossmodal facilitation is only observed at visual field locations overlapping with the sound, whereas crossmodal inhibition affects the whole hemifield. Furthermore, we tested whether multisensory perceptual learning with misaligned audio-visual stimuli reshapes crossmodal facilitation and inhibition. We found that training shifts crossmodal facilitation towards the trained location without changing its range. By contrast, training narrows the range of inhibition without shifting its position. Our results suggest that crossmodal facilitation and inhibition reflect separate mechanisms that can both be reshaped by multisensory experience even in adult humans. Multisensory links seem to be more plastic than previously thought.     

Effects of task-irrelevant cues and reinforcement delay on choice-escape learning following inescapable shock: evidence for a deficit in selective attention

Prior exposure to inescapable shock has been reported to interfere with choice-escape learning, but several investigators have failed to obtain this effect. A series of five experiments examined the conditions under which choice-escape learning in an automated Y-maze is impaired by pretreatment with inescapable shock. Inescapably shocked rats made more errors and responded more slowly than did controls only when shock termination was delayed and task-irrelevant cues were present during choice-escape training. These findings are discussed in terms of information processing and neurochemical consequences of exposure to inescapable shock.     

The perceptual span and peripheral cues in reading

Skilled readers read passages that were displayed on a Cathode Ray Tube controlled by a computer. The readers' eye movements were monitored and certain critical words were changed by the computer as the eye was in motion. The experimental technique utilized in the study provided data on how wide the area is from which a reader acquires information during a fixation in silent reading. The results also delineate different types of visual information that are acquired from various areas within the perceptual span. It was found that a reader was able to make a semantic interpretation of a word that began 1–6 character spaces from his fixation point. When he fixated 7–12 character spaces prior to a word, he was able to pick up such gross visual characteristics as word shape and initial and final letters. It was concluded that the skilled reader is able to take advantage of information in the periphery. However, the size of the area from which he does is rather small.     

Incremental learning of perceptual and conceptual representations and the puzzle of neural repetition suppression

Incremental learning models of long-term perceptual and conceptual knowledge hold that neural representations are gradually acquired over many individual experiences via Hebbian-like activity-dependent synaptic plasticity across cortical connections of the brain. In such models, variation in task relevance of information, anatomic constraints, and the statistics of sensory inputs and motor outputs lead to qualitative alterations in the nature of representations that are acquired. Here, the proposal that behavioral repetition priming and neural repetition suppression effects are empirical markers of incremental learning in the cortex is discussed, and research results that both support and challenge this position are reviewed. Discussion is focused on a recent fMRI-adaptation study from our laboratory that shows decoupling of experience-dependent changes in neural tuning, priming, and repetition suppression, with representational changes that appear to work counter to the explicit task demands. Finally, critical experiments that may help to clarify and resolve current challenges are outlined.     

Imprinting and perceptual learning

Filial responses are first considered by reference to the initial stimulus situations. Findings on variability in responsiveness of chicks are reported and discussed. Facilitated responsiveness subsequent to visual stimulation is reported. The concept of critical period is examined in the light of other workers' and our own findings; it is concluded that imprinting ends as a result of its own action rather than through the effects of fear. Following responses are further considered by reference to the influences of early experiences and the act of following upon the occurrence and strength of subsequent responses. The degree of attachment to a moving object tends to be proportional to the amount of experience. Individual chicks were allowed to spend several hours following a box in a runway and their ability to discriminate between familiar and unfamiliar moving objects and static environments was studied. Strong evidence for imprintability to environment has been found. Imprinting phenomena are discussed in terms of perceptual learning.     

Target selection during bimanual reaching to direct cues is unaffected by the perceptual similarity of the targets

Investigations of bimanual movements have shed considerable insight on the constraints underlying our ability to perform coordinated actions. One prominent limitation is evident when people are required to produce reaching movements in which the two trajectories are of different amplitudes and/or directions. This effect, however, is only obtained when the movements are cued symbolically (e.g., letters indicate target locations); these planning costs are absent when the target locations are directly cued (J. Diedrichsen, E. Hazeltine, S. Kennerley, & R. B. Ivry, 2001). The present experiments test whether the absence of planning costs under the latter condition is due to the perceptual similarity of the direct cues. The results demonstrate that measures of response planning and execution do not depend on the perceptual similarity of the direct cues. Limitations in our ability to perform distinct actions with the two hands appear to reflect interactions related to response selection involving the translation of symbolic cues into their associated movements rather than arise from interactions associated with perception, motor programming, and motor execution.     

Enhancement and suppression effects resulting from information structuring in sentences

Information structuring through the use of cleft sentences increases the processing efficiency of references to elements within the scope of focus. Furthermore, there is evidence that putting certain types of emphasis on individual words not only enhances their subsequent processing, but also protects these words from becoming suppressed in the wake of subsequent information, suggesting mechanisms of enhancement and suppression. In Experiment 1, we showed that clefted constructions facilitate the integration of subsequent sentences that make reference to elements within the scope of focus, and that they decrease the efficiency with reference to elements outside of the scope of focus. In Experiment 2, using an auditory text-change-detection paradigm, we showed that focus has similar effects on the strength of memory representations. These results add to the evidence for enhancement and suppression as mechanisms of sentence processing and clarify that the effects occur within sentences having a marked focus structure.     

Procedural learning in perceptual categorization

In two experiments, observers learned two types of category structures: those in which perfect accuracy could be achieved via some explicit rule-based strategy and those in which perfect accuracy required integrating information from separate perceptual dimensions at some predecisional stage. At the end of training, some observers were required to switch their hands on the response keys, whereas the assignment of categories to response keys was switched for other observers. With the rule-based category structures, neither change in response instructions interfered with categorization accuracy. However, with the information-integration structures, switching response key assignments interfered with categorization performance, but switching hands did not. These results are consistent with the hypothesis that abstract category labels are learned in rule-based categorization, whereas response positions are learned in information-integration categorization. The association to response positions also supports the hypothesis of a procedural-learning-based component to information integration categorization.     

Acetylcholine and olfactory perceptual learning

Olfactory perceptual learning is a relatively long-term, learned increase in perceptual acuity, and has been described in both humans and animals. Data from recent electrophysiological studies have indicated that olfactory perceptual learning may be correlated with changes in odorant receptive fields of neurons in the olfactory bulb and piriform cortex. These changes include enhanced representation of the molecular features of familiar odors by mitral cells in the olfactory bulb, and synthetic coding of multiple coincident odorant features into odor objects by cortical neurons. In this paper, data are reviewed that show the critical role of acetylcholine (Ach) in olfactory system function and plasticity, and cholinergic modulation of olfactory perceptual learning at both the behavioral and cortical level.     

知觉线索对元记忆监控的影响

近年来, 越来越多的证据表明知觉线索影响个体的高级认知--元记忆。元记忆指个体对自己学习和记忆活动的认知, 其核心成分是监测和控制。研究发现, 多种知觉线索(如字体大小、音量、文本清晰度、重量、亮度等)影响个体的元记忆监测(如学习判断和自信心评定)及控制(如学习时间分配)。这种影响可能是加工流畅性所致, 也可能基于人们的信念产生。未来研究有必要进一步探究知觉线索影响元记忆监控的条件, 并厘清加工流畅性和信念的具体作用。     

An asymmetry in transmodal perceptual learning

Transmodal perceptual learning was examined in a canonical same/different paradigm. Subjects naive to vibrotactile stimulation and unfamiliar with the task were asked to discriminate sequentially presented shapes moving laterally across an aperture. On all trials, the shapes were presented either visually and then vibrotactually or in the opposite modality order, and on all trials the shapes moved in opposite directions. Analyses of the data revealed that although perceptual learning was evident in both groups, the rate of the learning was more rapid in the visual-vibrotactile group. This interaction of modality order and practice was significant and was considered in terms of E.J. Gibson's theory of perceptual learning and in terms of the constructs, suggested by J.J. Gibson, of available and accessible information-in-stimulation and the education of attention.     

Kinematic cues in perceptual weight judgement and their origins in box lifting

When accepting a parcel from another person, we are able to use information about that person’s movement to estimate in advance the weight of the parcel, that is, to judge its weight from observed action. Perceptual weight judgment provides a powerful method to study our interpretation of other people’s actions, but it is not known what sources of information are used in judging weight. We have manipulated full form videos to obtain precise control of the perceived kinematics of a box lifting action, and use this technique to explore the kinematic cues that affect weight judgment. We find that observers rely most on the duration of the lifting movement to judge weight, and make less use of the durations of the grasp phase, when the box is first gripped, or the place phase, when the box is put down. These findings can be compared to the kinematics of natural box lifting behaviour, where we find that the duration of the grasp component is the best predictor of true box weight. The lack of accord between the optimal cues predicted by the natural behaviour and the cues actually used in the perceptual task has implications for our understanding of action observation in terms of a motor simulation. The differences between perceptual and motor behaviour are evidence against a strong version of the motor simulation hypothesis. A. F. de C. Hamilton and D. W. Joyce have contributed equally to this work.