Discrete vs. continuous processing: The fate of an incompletely processed perceptual dimension

A relevant issue in the debate on continuous vs. discrete processing of information is whether incompletely processed information does or does not affect a subsequent reaction. Two stimuli (SL, SR) were presented on eye level, subtending a visual angle of 45 degrees. SL was always inspected first, followed by a saccade to SR and finally by a same/different response. The fixation time of SL (TL), the saccadic time (TM) and the time from fixating SR to the response (TR) were separately measured. SL and SR consisted of two-dimensional stimuli (size and letter shape) constructed in such a way that encoding size took longer for one group and encoding shape took longer for another group of 10 subjects. All subjects were tested in three conditions: Shape was relevant in one, size in the second, and both dimensions were relevant in the third condition.

TL was less when encoding the relevant dimension was fast. When both dimensions were relevant, TL was about as long as when only the slow dimension was relevant, suggesting parallel and interference-free processing during TL. When only the slow dimension was relevant, TR (same) was much longer when the fast dimension differed. When the fast dimension was relevant, TR (same) was slightly longer when the slow dimension differed, which can be handled by either model. The experiment was repeated with three well-practiced and less variable subjects who carried out sufficient trials to measure TR as a function of TL. The results of this study were in line with the discrete model: A different slow and irrelevant dimension did not affect the same response regardless of the duration of TL. Interestingly, subjects were capable of retrieving the slow dimension, suggesting a code which can be used for retrieval but which does not affect the same/different response.     

Discrete versus continuous stage models of human information processing: in search of partial output

This article introduces a new technique designed to study the flow of information through processing stages in choice reaction time tasks. The technique was designed to determine whether response preparation can begin before stimulus identification is complete ("continuous" models), or if a stimulus must be fully identified prior to any response activation ("discrete" models). To control the information available at various times during stimulus identification, some relevant stimulus characteristics were made easy to discriminate and some were made hard to discriminate. The experimental strategy was to look for effects of partial output based on information conveyed by characteristics that were easy to discriminate. The technique capitalized on the fact, demonstrated in Experiment 1, that preparation of two response fingers on the same hand is more effective than preparation of two response fingers on different hands. The usefulness of partial output was varied by manipulating the assignments of stimuli to responses. For some mappings partial information could contribute to effective response preparation because the responses consistent with partial information were assigned to fingers on the same hand. For other mappings partial information could not contribute to effective response preparation because the responses consistent with partial information were assigned to fingers of different hands. Performance differences between these mappings were considered evidence that partial information about a stimulus was transmitted to response activation processes before the stimulus was uniquely identified, and thus were considered evidence against discrete transmission of information about the stimulus as a whole. A variety of stimulus sets were studied; the results suggest that information is transmitted discretely with respect to stimulus codes, although distinct codes activated by a single stimulus may be transmitted at different times.     

ROC and z-ROC analysis in recognition memory: continuous, threshold, and asymmetric models

In this research, we applied the operating characteristic of the receiver (ROC) to evaluate item-recognition memory by means of open class words (CA) and closed class words (CC). The purpose was to evaluate memory processes and models, according to the type of stimuli used: words in Spanish, classified according to grammar characteristics. To register the data, a rating scale was applied to obtain the appropriate response levels. Statistically significant differences between the processing of both types of words were obtained. We evaluated models of threshold, continuous, and unequal variance. As a result, we could contribute to the resolution of the present controversy about the models adapted to evaluate the memory of item recognition. Lastly, the differentiation and integration of the models from an empirical point of view is discussed.     

The influence of the number of alternatives on the perceptual recognition threshold

A study of the recognition thresholds for nonsense syllables previously presented in lists containing from 2 to 15 syllables is reported. The threshold is found to increase in proportion to the logarithm of the number of alternatives (i.e. the length of the list from which a given test syllable is drawn). It is therefore concluded that recognition threshold is a function of the amount of information transmitted.     

Contribution of perceptual fluency to recognition judgments.

Following a shallow (count vowels) or deep (read) study task, old and new words were tested for both fluency of perception and recognition memory. Subjects first identified a test word as it came gradually into view and then judged it as old or new. Old words were identified faster than new words, indicating implicit, perceptual memory for old words. Independently of this effect, words judged old were identified faster than words judged new, especially after shallow study. Eight experiments examined the possible causal relationship between perceptual fluency and recognition judgements. Experiments 1 to 4 showed that fast identifications per se do not promote old judgments. Accelerating the identification of test items by semantically priming them or making them come more quickly into view did not affect recognition judgments. Experiment 5 showed that the usual association of fast identifications with old judgments is not an artifact of item selection because the association disappeared when the identifications and judgements were segregated into different phases of the test task. Experiments 6 and 7 showed tha the likelihood of old judgments increases directly with the pretested perceptibility of test words, but only after shallow study. Experiment 8 showed that the dependency of recognition judgments on perceptual fluency continues to hold when the requirement to identify the words before judging them is eliminated. We conclude that fluency of perception contributes to recognition judgments, but only when the fluency is produced naturally (e.g., through perceptual memory) and explicit memory is minimal.     

Visual-auditory events: cross-modal perceptual priming and recognition memory.

Modality specificity in priming is taken as evidence for independent perceptual systems. However, Easton, Greene, and Srinivas (1997) showed that visual and haptic cross-modal priming is comparable in magnitude to within-modal priming. Where appropriate, perceptual systems might share like information. To test this, we assessed priming and recognition for visual and auditory events, within- and across- modalities. On the visual test, auditory study resulted in no priming. On the auditory priming test, visual study resulted in priming that was only marginally less than within-modal priming. The priming results show that visual study facilitates identification on both visual and auditory tests, but auditory study only facilitates performance on the auditory test. For both recognition tests, within-modal recognition exceeded cross-modal recognition. The results have two novel implications for the understanding of perceptual priming: First, we introduce visual and auditory priming for spatio-temporal events as a new priming paradigm chosen for its ecological validity and potential for information exchange. Second, we propose that the asymmetry of the cross-modal priming observed here may reflect the capacity of these perceptual modalities to provide cross-modal constraints on ambiguity. We argue that visual perception might inform and constrain auditory processing, while auditory perception corresponds to too many potential visual events to usefully inform and constrain visual perception.     

Development of perceptual expertise in emotion recognition

How do children’s early social experiences influence their perception of emotion-specific information communicated by the face? To examine this question, we tested a group of abused children who had been exposed to extremely high levels of parental anger expression and physical threat. Children were presented with arrays of stimuli that depicted the unfolding of facial expressions, from neutrality to peak emotions. The abused children accurately recognized anger early in the formation of the facial expression, when few physiological cues were available. The speed of children’s recognition was associated with the degree of anger/hostility reported by the child’s parent. These data highlight the ways in which perceptual learning can shape the timing of emotion perception.     

Units of episodic memory in perceptual recognition

Two studies examined the cognitive units of sentence memory using a perceptual recognition task. Four candidate cognitive units were considered: concepts, propositions, integrated propositions, and nonintegrated propositions. Subjects first received a list of acquisition sentences and then were asked to reproduce sentences presented under a white-noise mask. These masked sentences were replicas of the acquisition sentences, were formed of recombined clauses from the acquisition sentences, or were formed of recombined words from the acquisition sentences. Reproduction accuracy was employed as the dependent measure. Results supported propositions (operationalized by clauses) as cognitive units of episodic memory. No conclusive evidence was obtained for concepts, integrated propositions, or nonintegrated propositions as cognitive units. The utility of perceptual recognition tasks for studying the cognitive units of episodic memory is discussed.     

The role of transparency in perceptual grouping and pattern recognition.

The shortest stimulus exposure time for which transparency can be seen was examined. In the first experiment, overlapping digits were presented for 120 ms and the luminance in the overlapping regions was varied. Subjects reported, in separate blocks of trials, either the apparent transparency of the digits or the identity of the digits. When the luminance was set so that one set of digits appeared to be seen through the other, recognition of the digits was high. When the luminance in the overlapping regions did not produce impressions of transparency, digit recognition was low. In the second experiment, digit identification at several stimulus durations was compared between stimuli that had luminance that was valid for transparency and stimuli that had invalid luminance. Performance was found to be higher in the valid luminance condition than in the invalid condition after as little as 60 ms exposure duration. This result suggests that the impression of transparency requires only relatively short exposure durations.     

Holographic and trace strength models of rehearsal effects in the item recognition task

Two models are described that are capable of generating latency predictions in the item recognition task based on the sequence and timing of rehearsals. It is shown that equal positive and negative slopes are possible when the average number of rehearsals per item increases with list length but that when no rehearsal occurs the positive slope is predicted to be substantially steeper than the negative. Serial position effects are also analyzed for the various rehearsal strategies seen when subjects are asked to rehearse out loud.     

Emotion recognition in schizophrenia: further investigation of generalized versus specific deficit models

In this study, the authors examined the nature of emotion perception in schizophrenia. Two samples of people with schizophrenia, one receiving acute care for a recent exacerbation of symptoms and the other receiving extended care, were compared with a nonclinical control group on emotion perception and general perception measures. The nonclinical control group obtained the highest scores on all of the study measures, and the acutely ill group obtained the lowest scores. Furthermore, the acutely ill sample had a specific deficit in emotion perception that remained present after controlling for performance on the general perception tasks. Conversely, the deficits in emotion discrimination in the extended-care sample reflected generalized poor performance. Differences in performance on the emotion identification task between the 2 clinical groups were reduced when controlling for active symptoms.     

Culture and the physical environment. Holistic versus analytic perceptual affordances

Westerners' perceptions tend to focus on salient foreground objects, whereas Asians are more inclined to focus on contexts. We hypothesized that such culturally specific patterns of attention may be afforded by the perceptual environment of each culture. In order to test this hypothesis, we randomly sampled pictures of scenes from small, medium, and large cities in Japan and the United States. Using both subjective and objective measures, Study 1 demonstrated that Japanese scenes were more ambiguous and contained more elements than American scenes. Japanese scenes thus may encourage perception of the context more than American scenes. In Study 2, pictures of locations in cities were presented as primes, and participants' subsequent patterns of attention were measured. Both Japanese and American participants primed with Japanese scenes attended more to contextual information than did those primed with American scenes. These results provide evidence that culturally characteristic environments may afford distinctive patterns of perception.     

When preparation fails: disruptive effects of prior information on perceptual recognition.

There is a conflict in the literature on selective attention. Suppose a subject is briefly presented an item followed by a multiple-alternative recognition test. If the items are pictures, the subject's performance is facilitated by presenting the alternatives beforehand (a before facilitation), but when the items are letters the subjects' performance is disrupted by presenting the alternatives beforehand (a before disruption). Five experiments were conducted to resolve this conflict, and all involved a comparison of tachistoscopic recognition when alternatives were either presented beforehand or not. The first two studies showed that the before disruption with letters was not due to certain task parameters. Experiments 3-5 demonstrated that this effect was due to masking conditions. Experiments 3 and 4 revealed that the disruption occurred only when a mask is used, while the last experiment indicated the disruption effect was sensitive to the type of mask employed. Preseumably, the before disrption arises because a subject erroneously considers the features of a mask along with those of the test item in arriving at a perceptual decision.     

The neural correlates of conceptual and perceptual false recognition

False recognition, broadly defined as a claim to remember something that was not encountered previously, can arise for multiple reasons. For instance, a distinction can be made between conceptual false recognition (i.e., false alarms resulting from semantic or associative similarities between studied and tested items) and perceptual false recognition (i.e., false alarms resulting from physical similarities between studied and tested items). Although false recognition has been associated with frontal cortex activity, it is unclear whether this frontal activity can be modulated by the precise relationship between studied and falsely remembered items. We used event-related fMRI to examine the neural basis of conceptual compared with perceptual false recognition. Results revealed preferential activity in multiple frontal cortex regions during conceptual false recognition, which likely reflected increased semantic processing during conceptual (but not perceptual) memory errors. These results extend recent reports that different types of false recognition can rely on dissociable neural substrates, and they indicate that the frontal activity that is often observed during false compared with true recognition can be modulated by the relationship between studied and tested items.     

Discrete and continuous measures of dimensional stimulus control

In two sets of experiments, we examined dimensional stimulus control of pigeons' responses to a visual flicker-rate continuum. In the first experiment, responses to a single key were reinforced periodically during stimuli from one half of the stimulus continuum, and responses during other stimuli were extinguished. In the second experiment, two response keys were simultaneously available, with reinforcement for each response alternative associated with different halves of the stimulus continuum. Conditions of the second experiment involved either free-operant or discrete-trial stimulus presentations. Results from these experiments show that positive dimensional contrast appeared in discrimination tasks with one or two response alternatives, but only with free-operant procedures. In addition, discrimination between stimulus classes established by differential reinforcement was assessed as accurately by continuous rate measures as by discrete response choice in the two-alternative situation. The general implication of these experiments is that response rate measures, when properly applied, may reveal sources of variation within stimulus classes, such as dimensional contrast, that are not evident with discrete measures.     

Long-term perceptual specificity effects in recognition memory: the transformed pictures paradigm.

The effects of a study/test mismatch in the viewing mode of natural scenes on recognition memory performance were examined. At both encoding and retrieval, scenes were presented either by being divided into quarters that were displayed in a sequential cumulative fashion or by scrolling the images through the screen, thereby gradually revealing the content of the images. Half of the participants were tested immediately after encoding and the other half after 48 hours. For both the immediate and delayed retrieval conditions, better recognition memory was demonstrated when viewing modes matched across study and test than when they mismatched. Implications for current processing and multiple systems views of memory are discussed.     

Reevaluation of two models for judgments of perceptual intervals

In Marks and Cain’s (1972) experiment, 12 Ss estimated magnitudes of stimuli presented one at a time and differences in magnitudes of stimuli presented in pairs for heaviness of weight, roughness of emery papers, and area of circles. Their results appeared inconsistent with the two-stage model of magnitude estimation. But the expressions fitted to the data were different from those previously used in tests of the model. An additive constant was omitted. A reanalysis of their data with the constant included yielded support for the model for all three continua. An alternative model proposed by Marks and Cain was reasonably consistent with the da~a for weight, while inconsistent with the data for roughness and area.