Contextual dependencies in a stimulus equivalence paradigm

Two experiments with human subjects assessed contextual dependencies in a stimulus equivalence paradigm. Subjects learned to form two sets of stimuli in a matching-to-sample training procedure. Each set was presented against one of two different background colours, the contextual cues. At test, the influence of a context change--that is, presenting each set against the other context--was measured on baseline, symmetry, and equivalence trials. These three trial types reflect a difference in task complexity. It was predicted that the magnitude of context-dependent effects would be a positive function of task complexity. In Experiment 1, the context change was realized by switching the stimulus set at test while keeping the background colour constant. In Experiment 2, the stimulus set remained constant, and the background colour was switched. In both experiments, a change in context only resulted in an increase in response latency on equivalence trials; no effect was seen on symmetry and baseline trials. Results were discussed in the framework of switch costs, habituation to contextual stimuli, and a model based on Shea and Wright (1995) that explains the differential influence of a context switch on easy versus difficult tasks.     

Stimulus and response factors in mirror-image discrimination

Two choice-reaction time studies assessed the influence of stimulus-response mapping, stimulus complexity, and stimulus alignment on adults’ discrimination of mirror-image and nonmirror-image stimulus pairs. Half the subjects in Experiment 1 were instructed to treat nonmiiTor pairs as “same” and mirror pairs as “different”; the other half responded in the opposite manner. The first group responded more quickly to nonmirror pairs, while the second group responded more quickly to mirror pairs. This result, which held for horizontal stimuli (side by side) as well as for vertical stimuli (one above the other), confirms the importance of experiential factors in mirror-image “confusions. “ In Experiment 2. stimuli were drawn from a population of patterns whose complexity could be objectively defined. In general, the more complex the pattern, the slower the response and complexity seemed to influence the qualitative nature of pattern processing. In both experiments, subjects responded more quickly to horizontal stimuli than to vertical stimuli.     

Parallel memory retrieval in dual-task situations: II. Episodic memory

Three experiments asked whether subjects could retrieve information from a 2nd stimulus while they retrieved information from a 1st stimulus. Subjects performed recognition judgments on each of 2 words that followed each other by 0, 250, and 1,000 ms (Experiment 1) or 0 and 300 ms (Experiments 2 and 3). In each experiment, reaction time to both stimuli was faster when the 2 stimuli were both targets (on the study list) or both lures (not on the study list) than when 1 was a target and the other was a lure. Each experiment found priming from the 2nd stimulus to the 1st when both stimuli were targets. Reaction time to the 1st stimulus was faster when the 2 targets came from the same memory structure at study (columns in Experiment 1; pairs in Experiment 2; sentences in Experiment 3) than when they came from different structures. This priming is inconsistent with discrete serial retrieval and consistent with parallel retrieval.     

Perceptual differentiation as a source of category effects in object processing: Evidence from naming and object decision

The locus of category effects in picture recognition and naming was examined in two experiments with normal subjects. Subjects carried out object decision (deciding whether the stimulus is a “real” object or not) and naming tasks with pictures of clothing, furniture, fruit, and vegetables. These categories are distinguished by containing either relatively many exemplars with similar perceptual structures (fruit and vegetables;structurally similar categories), or relatively few exemplars with similar perceptual structures (clothing and furniture;structurally dissimilar categories). In Experiment 1, responses to the stimuli from the structurally similar categories were slower than responses to stimuli from the structurally dissimilar categories, and this effect was larger in the naming than in the object decision task. Further, prior object decisions to stimuli from structurally similar categories facilitated their subsequent naming. In Experiment 2, we orthogonally manipulated object decision and naming as prime and target tasks, again with stimuli from the four categories. Category effects, with responses slower to objects from structurally similar categories, were again larger in naming than in object decision, and these category effects in naming were reduced by priming with both naming and object decision. We interpret the data to indicate that category effects in object naming can reflect visually based competition which is reduced by the preactivation of stored structural knowledge for objects.     

Detection and Identification of Change in Naturalistic Scenes

Research using change detection paradigms has demonstrated that only limited scene information remains available for conscious report following initial inspection of a scene. Previous researchers have found higher change identification rates for deletions of parts of objects in line drawings of scenes than additions. Other researchers, however, have found an asymmetry in the opposite direction for addition/deletion of whole objects in line drawings of scenes. Experiment 1 investigated subjects' accuracy in detecting and identifying changes made to successive views of high quality photographs of naturalistic scenes that involved the addition and deletion of objects, colour changes to objects, and changes to the spatial location of objects. Identification accuracy for deletions from scenes was highest, with lower identification rates for object additions and colour changes, and the lowest rates for identification of location changes. Data further suggested that change identification rates for the presence/absence of objects were a function of the number of identical items present in the scene. Experiment 2 examined this possibility further, and also investigated whether the higher identification rates for deletions found in Experiment 1 were found for changes involving whole objects or parts of objects. Results showed higher identification rates for deletions, but only where a unique object was deleted from a scene. The presence of an identical object in the scene abolished this deletion identification advantage. Results further showed that the deletion/addition asymmetry occurs both when the objects are parts of a larger object and when they are entire objects in the scene.     

Locus of the effect of specific practice in continuous visual search

Specific practice in a visual search task can result either in a selective elaboration of the feature lists of the task stimuli or in a selective emphasis of their status within the task (targets vs. nontargets). According to the first explanation, which is related to the differentiation principle of perceptual learning, specific practice enhances the operation of stimulus identification. According to the second explanation, which is related to the enrichment principle of perceptual learning, it enhances the operation of response selection. Evidence from two transfer experiments with a reversal paradigm argues in favor of the second view, at least for tasks with easily codable letter stimuli. The results are discussed in the framework of a recent model of information integration in visual search.     

Establishing Arbitrary Stimulus Classes via Identity-matching Training and Non-reinforced Matching with Complex Stimuli

The present study investigated whether training on an identity match-to-sample task followed by non-reinforced matching probes with complex stimuli leads to the emergence of multiple arbitrary matching performances and arbitrary stimulus classes in preschool children. In Experiment 1, eight subjects were trained on a colour-matching task (A-A). Then they received tests with complex AB and AC colour-form stimuli (AB-A, B-AB; AC-A, C-AC). These tasks were designed to help subjects respond to both elements of each complex stimulus. Subsequent B-A, C-A, A-B, A-C, B-C, and C-B tests revealed that all subjects had acquired class-consistent colour-form and form-form relations. Experiment 2 examined whether these results could be replicated when subjects were encouraged to respond to the colour elements of some (AB) complex stimuli and to the form elements of other (AC) stimuli. The procedures were the same as in Experiment 1 except that during the first test only A-AB and C-AC tasks were used. Six of eight subjects demonstrated all tested relations.     

Retinal location and its effect on the processing of target and distractor information

Two experiments were conducted to study the perceptual facilitation and inhibition that occurs between foveal and parafoveal or peripheral regions of the eye. Experiment 1 used a Stroop task to compare color detection latencies of foveal and parafoveal targets. The target and distractor components of the Stroop stimuli were separated and presented with varied stimulus onset asynchronies. Experiment 2 used a Stroop-like task to replicate and extend the findings into the visual periphery. Subjects were found to process foveally presented distractor information while attending to targets presented in parafoveal or peripheral regions of the eye. Distractor information that was incompatible was suppressed while compatible information was used to facilitate target processing. When the targets were presented foveally along with the distractor information, subjects appeared to automatically process the distractor information. The findings are discussed within the framework of past studies that presented subjects with competing tasks across retinal location. The implications of these findings to a two-process theory of attention are also considered.     

Visuo‐spatial working memory in navigation

Two experiments employed dual task techniques to explore the role of working memory in route learning and subsequent route retrieval. Experiment 1 involved contrasting performance of two groups of volunteers respectively learning a route from a series of map segments or a series of visually presented nonsense words. Both groups performed learning and recognition under articulatory suppression or concurrent spatial tapping. Both concurrent tasks had an overall disruptive effect on each learning task. However, spatial tapping disrupted route recognition rather more than did articulatory suppression, while the nonsense word recognition was impaired more by articulatory suppression than by concurrent spatial tapping. Experiment 2 again used dual task methodology, but explored route learning by asking volunteers to follow the experimenter through the winding streets of a medieval European town centre. Retrieval involved following the same route while the experimenter followed and noted errors in navigation. Overall the results partially replicated those of Experiment 1 in that both concurrent tasks interfered with route learning. However, volunteers with high spatial ability appeared more affected by the concurrent spatial tapping task, whereas low spatial subjects appeared more affected by the concurrent articulatory suppression task. Results are interpreted to suggest that different aspects of working memory are involved in learning a route from a map with a greater emphasis on visuo‐spatial resources, but in tasks set in real environments where many cues of a varied nature are available, only high spatial ability subjects appear to rely heavily upon the visuospatial component of working memory. Copyright © 2002 John Wiley & Sons, Ltd.     

Unconscious processing of color and form in metacontrast masking

Three experiments employed a metacontrast masking procedure to examine the extent and nature of priming effects from visual stimuli not consciously perceived. The results showed effects of unconscious stimuli on subsequent target responses that (1) were more consistent, reliable, and not subject to strategic control, as compared with consciously perceived stimuli (Experiment 1); (2) produced both facilitation and interference of subsequent processing (Experiment 2); and (3) did not influence indirect response-related levels of processing (Experiment 3). These results demonstrate that color and form attributes of unconscious stimuli are sufficiently registered within the visual system to influence behavior, and that some of these unconscious effects occur at early levels of stimulus encoding, prior to higher level perceptual and response-related processes.     

Verbal overshadowing of visual memories: some things are better left unsaid

It is widely believed that verbal processing generally improves memory performance. However, in a series of six experiments, verbalizing the appearance of previously seen visual stimuli impaired subsequent recognition performance. In Experiment 1, subjects viewed a videotape including a salient individual. Later, some subjects described the individual's face. Subjects who verbalized the face performed less well on a subsequent recognition test than control subjects who did not engage in memory verbalization. The results of Experiment 2 replicated those of Experiment 1 and further clarified the effect of memory verbalization by demonstrating that visualization does not impair face recognition. In Experiments 3 and 4 we explored the hypothesis that memory verbalization impairs memory for stimuli that are difficult to put into words. In Experiment 3 memory impairment followed the verbalization of a different visual stimulus: color. In Experiment 4 marginal memory improvement followed the verbalization of a verbal stimulus: a brief spoken statement. In Experiments 5 and 6 the source of verbally induced memory impairment was explored. The results of Experiment 5 suggested that the impairment does not reflect a temporary verbal set, but rather indicates relatively long-lasting memory interference. Finally, Experiment 6 demonstrated that limiting subjects' time to make recognition decisions alleviates the impairment, suggesting that memory verbalization overshadows but does not eradicate the original visual memory. This collection of results is consistent with a recording interference hypothesis: verbalizing a visual memory may produce a verbally biased memory representation that can interfere with the application of the original visual memory.     

A comparison of generalization functions and frame of reference effects in different training paradigms

Six experiments were carried out to compare go/no-go and choice paradigms for studying the effects of intradimensional discrimination training on subsequent measures of stimulus generalization in human subjects. Specifically, the purpose was to compare the two paradigms as means of investigating generalization gradient forms and frame of reference effects. In Experiment 1, the stimulus dimension was visual intensity (brightness); in Experiment 2, it was line orientation (line-angle stimuli). After learning to respond (or to respond “right”) to stimulus value (SV) 4 and not to respond (or to respond “left”) to SV2 (in Experiment 1) or SV1 (in Experiment 2), the subjects were tested for generalization (recognition) with an asymmetrical set of values ranging from SV1 to SV11. Go/no-go training produced peaked gradients, whereas choice training produced sigmoid gradients. The asymmetrical testing resulted in a gradual shift of the peak of responding (go/no-go group) or in the point of subjective indifference (PSI; choice group) toward. the central value of the test series; thus, both paradigms revealed a frame of reference effect. The results were comparable for the quantitative (intensity) and the qualitative (line-angle) stimulus dimensions. Experiment 3 compared the go/no-go procedure with a yes/no procedure in which subjects responded “right” to SV4 and “left” to all other intensities and found no differences between these procedures. Thus the difference in gradient forms in go/no as opposed to (traditional) choice paradigms depends on whether one or two target stimuli are used in training. In Experiment 4, in which visual intensity was used, the shift in the PSI following choice training varied positively with the range of asymmetrical test stimuli employed. In Experiment 5, also with visual intensity, the magnitude of the peak shift following go/no-go training varied as a function of over representing a high or a low stimulus value during generalization testing. Experiment 6, with line angles, showed that the PSI following choice training varies in a similar way. The frame of reference effects obtained in these experiments are consistent with an adaptation-level model.     

A comparison of generalization functions and frame of reference effects in different training paradigms.

Six experiments were carried out to compare go/no-go and choice paradigms for studying the effects of intradimensional discrimination training on subsequent measures of stimulus generalization in human subjects. Specifically, the purpose was to compare the two paradigms as means of investigating generalization gradient forms and frame of reference effects. In Experiment 1, the stimulus dimension was visual intensity (brightness); in Experiment 2, it was line orientation (line-angle stimuli). After learning to respond (or to respond "right") to stimulus value (SV) 4 and not to respond (or to respond "left") to SV2 (in Experiment 1) or SV1 (in Experiment 2), the subjects were tested for generalization (recognition) with an asymmetrical set of values ranging from SV1 to SV11. Go/no-go training produced peaked gradients, whereas choice training produced sigmoid gradients. The asymmetrical testing resulted in a gradual shift of the peak of responding (go/no-go group) or in the point of subjective indifference (PSI; choice group) toward the central value of the test series; thus, both paradigms revealed a frame of reference effect. The results were comparable for the quantitative (intensity) and the qualitative (line-angle) stimulus dimensions. Experiment 3 compared the go/no-go procedure with a yes/no procedure in which subjects responded "right" to SV4 and "left" to all other intensities and found no differences between these procedures. Thus the difference in gradient forms in go/no as opposed to (traditional) choice paradigms depends on whether one or two target stimuli are used in training. In Experiment 4, in which visual intensity was used, the shift in the PSI following choice training varied positively with the range of asymmetrical test stimuli employed. In Experiment 5, also with visual intensity, the magnitude of the peak shift following go/no-go training varied as a function of overrepresenting a high or a low stimulus value during generalization testing. Experiment 6, with line angles, showed that the PSI following choice training varies in a similar way. The frame of reference effects obtained in these experiments are consistent with an adaptation-level model.     

Decision latencies of “same” and “different” judgments

When a subject is asked to judge whether two stimuli are “same” or“different,” the time he takes to reach the decision same is frequently unequal to the time he takes to reach the decision different. We studied this discrepancy as a function of several variables, including stimulus modality, “codability” vs.“noncodability” of test stimuli, interstimulus interval, and discrimination difficulty. Results of four different experiments performed on a total of 111 subjects showed codability and discrimination difficulty to be the most important factors. Stimuli that are codable (i.e., which can be categorized by absolute judgment) yield a shorter latency for decision same, and noncodable stimuli (i.e., those requiring a reference stimulus for categorization) yield a longer latency for decision same. The modality of test stimuli, the prothetic or metathetic nature of the dimension to be judged, and simultaneous vs. successive presentation of the stimuli appear not to be crucial factors.     

Combining experiences over time: the effects of duration,intensity changes and on-line measurements on retrospective pain evaluations

Two experiments were conducted to examine the effects of various factors on retrospective pain evaluation. The factors examined in Experiment 1 were the rate and pattern of change, the intensity (particularly the final intensity), and the duration of the painful experience. Experiment 2 manipulated these factors and, in addition, examined the effect of continuous (on-line) ratings on the overall retrospective evaluation. The two experiments utilized different pain modalities, heat in the first and mechanical pressure in the second. In addition, all subjects in Experiment 1 experienced stimuli with the same physical magnitude, while in Experiment 2 stimuli were individually tailored to make them subjectively equivalent. In both experiments, subjects were presented with a series of painful stimuli and evaluated the intensity of each stimulus immediately upon its termination. The stimuli themselves were composed of multiple intensity levels that differentially changed over time (Intensity-Patterns). Subjects' on-line ratings in Experiment 2 closely mirrored the physical patterns of the intensities. The main conclusion from both experiments is that the retrospective evaluations of painful experiences are influenced primarily by a combination of the final pain intensity and the intensity trend during the latter half of the experience. In addition, results indicated that duration has little impact on retrospective evaluations for stimuli of relatively constant intensity. However, when the stimulus intensity changes over time, duration does play a role. Finally, the task of continuously reporting the stimulus intensity had a moderating impact on the retrospective evaluations. © 1998 John Wiley & Sons, Ltd.     

Exposure effects on music preference and recognition

In three experiments, the effects of exposure to melodies on their subsequent liking and recognition were explored. In each experiment, the subjects first listened to a set of familiar and unfamiliar melodies in a study phase. In the subsequent test phase, the melodies were repeated, along with a set of distractors matched in familiarity. Half the subjects were required to rate their liking of each melody, and half had to identify the melodies they had heard earlier in the study phase. Repetition of the studied melodies was found to increase liking of the unfamiliar melodies in the affect task and to be best for detection of familiar melodies in the recognition task (Experiments 1, 2, and 3). These memory effects were found to fade at different time delays between study and test in the affect and recognition tasks, with the latter leading to the most persistent effects (Experiment 2). Both study-to-test changes in melody timbre and manipulation of study tasks had a marked impact on recognition and little influence on liking judgments (Experiment 3). Thus, all manipulated variables were found to dissociate the memory effects in the two tasks. The results are consistent with the view that memory effects in the affect and recognition tasks pertain to the implicit and explicit forms of memory, respectively. Part of the results are, however, at variance with the literature on implicit and explicit memory in the auditory domain. Attribution of these differences to the use of musical material is discussed.     

Task demands and representation in long-term repetition priming

The effects of task demands on the representation of letter strings in long-term repetition priming (LTRP) were explored in two lexical decision experiments. The stimuli in both experiments were words and nonwords, some presented horizontally and some vertically. The only difference between the two experiments was the response required by the participant. In Experiment 1, the participants pressed one of two buttons, indicating whether or not a given stimulus was a word. In Experiment 2, the participants pressed one of four buttons, indicating both the lexical status and the orientation of a given stimulus. The results were that in Experiment 1, LTRP was not disrupted by a change in stimulus orientation, whereas in Experiment 2 it was, suggesting that the nature of the stimulus representation utilized in LTRP is partially dependent on the demands of the task.     

不同注意条件下的知觉启动及其机制

采用快速命名方法探讨不同注意条件下的知觉启动效应及其机制。实验中呈现一系列颜色词,要求被试分别完成集中和分散注意任务,然后进行词命名和再认测验。在词命名任务中．实验1包括旧词、重组颜色词和新词,而在实验2中重组颜色词改为新颜色词。结果表明,在实验1中,只有在集中注意条件下,被试对旧词的命名时间明显短于重组颜色词．即表现出知觉启动效应。而在实验2的两种注意条件下,被试对旧词的命名时间均明显短于新颜色词。这提示,在不同注意条件下的学习会影响其后的颜色知觉启动,并且与词和颜色的联结捆绑有关。     

Visual form recognition threshold and the psychological refractory period

Two experiments studied the effect of a reaction time response (RT) on visual form recognition threshold when the temporal interval separating the RT stimulus and the recognition stimulus was short. In Experiment 1 an initial RT response to an auditory signal did not impair the subsequent forced-choice visual form recognition threshold. Interstimulus intervals (ISI) of 0, 50, 100, 150, and 200 msec were used; S was always aware of the ISI under test. In Experiment 2 a visual stimulus was used to elicit the R T response; this shift to an intramodal stimulus did not alter the recognition threshold. These data were interpreted as supporting the hypothesis that two stimulus events can be processed simultaneously even when the temporal interval between them is short.     

Semantic priming: subliminal perception or context?

Briefly presented, masked priming stimuli that cannot be identified by themselves can affect the processing of subsequent targets. The effect, which is sometimes viewed as a demonstration of unconscious processing, has been linked to the subliminal perception literature. Experiments 1 and 2 indicated that the identification of primes in the context of semantically related targets is superior to the identification of primes presented alone, and that the identification of primes in the context of semantically unrelated targets is inferior to the identification of primes presented alone. Experiment 3 indicated parallel findings in a recognition task. Consequently, an explanation of semantic priming in terms of the interactive nature of stimuli that are near to one another in time seems preferable to one based upon concepts of unconscious processing and subliminal perception.