Conceptual and perceptual processes in prospective remembering: differential influence of attentional resources

Does prospective remembering rely on strategic, attentionally demanding processes? We report three experiments suggesting that the extent to which attentional processes are required varies according to the character of ongoing task processing. Study-test changes in the semantic context of targets had a negative effect on prospective memory performance when participants were engaged in a conceptually focused (sentence verification) task (Experiment 1). Similarly, prospective remembering was lower following study-test changes in perceptual format (font) in the context of a perceptually focused (readability rating) ongoing task (Experiment 2). However, although dividing attention at retrieval had a negative effect during the performance of an ongoing conceptual task (Experiments 1 and 3), it had no effect during an ongoing perceptual task (Experiments 2 and 3). Thus, both perceptual and conceptual process are implicated in prospective remembering, but the processing focus of the task in which remembering should occur may mediate the requirement for strategic processes. These findings suggest that more than one retrieval route is available for prospective remembering and that selection of the route depends on the nature of the task and the processing that occurs at encoding and retrieval.     

Conceptual and perceptual processing in prospective remembering

McDaniel, Robinson-Riegler, and Einstein (1998) recently reported findings in support of the proposal that prospective remembering is largely conceptually driven. In each of the three experiments they reported, however, the task in which the prospective memory target was encountered at test had a predominantly conceptual focus, thereby potentially facilitating retrieval of conceptually encoded features of the studied target event. We report two experiments in which we manipulated the dimension (perceptual or conceptual) along which a target event varied between study and test while using a processing task, at both study and test, compatible with the relevant dimension of target change. When the target was encountered in a sentence validity task at study and test, and the semantic context in which a target was encountered was changed between these two occasions, prospective remembering declined (Experiment 1). A similar decline occurred, using a readability rating task, when the perceptual context (font in which the word was printed) was altered (Experiment 2). These results indicate that both perceptual and conceptual processes can support prospective remembering.     

Attention and perceptual priming in the perceptual identification task

Prior research indicates that manipulations of attention during encoding sometimes affect perceptual implicit memory. Two hypotheses were investigated. One proposes that manipulations of attention affect perceptual priming only to the extent that they disrupt stimulus identification. The other attributes reduced priming to the disruptive effects of distractor selection. The role of attention was investigated with a variant of the Stroop task in which participants either read words, identified their color, or did both. Identifying the color reduced priming even when the word was also overtly identified. This result held regardless of whether color and word were presented as a single object (Experiments 1 and 2) or as separate objects (Experiment 4). When participants read and identified a color, the overt order of the responses did not matter; both conditions reduced priming relative to reading alone (Experiment 3). The results provide evidence against the stimulus-identification account but are consistent with the distractor-selection hypothesis.     

Sensitivity to lateral information on a perceptual word identification task in French third and fifth graders

This study aimed at examining sensitivity to lateral linguistic and nonlinguistic information in third and fifth grade readers. A word identification task with a threshold was used, and targets were displayed foveally with or without distractors. Sensitivity to lateral information was inferred from the deterioration of the rate of correct word identification when displayed with distractors. Results show that the two reader groups were sensitive to both right and left lateral information. The area of sensitivity to this information was more extended for the identification of easy words than difficult words. Examination of the detrimental effect of distractors suggests that in both third and fifth graders, the impact of lateral information on foveal processing is the result of a general distraction effect, but also of linguistic processing whose nature remains to be clarified.     

Conceptual and perceptual priming and dissociation in chronic posttraumatic stress disorder

Cognitive models of posttraumatic stress disorder (PTSD) assert that memory processes play a significant role in PTSD (see e.g., Ehlers & Clark, 2000). Intrusive reexperiencing in PTSD has been linked to perceptual processing of trauma-related material with a corresponding hypothesized lack of conceptual processing. In an experimental study that included clinical participants with and without PTSD (N = 50), perceptual priming and conceptual priming for trauma-related, general threat, and neutral words were investigated in a population with chronic trauma-induced complaints as a result of the Troubles in Northern Ireland. The study used a new version of the word-stem completion task (Michael, Ehlers, & Halligan, 2005) and a word-cue association task. It also assessed the role of dissociation in threat processing. Further evidence of enhanced perceptual priming in PTSD for trauma stimuli was found, along with evidence of lack of conceptual priming for such stimuli. Furthermore, this pattern of priming for trauma-related words was associated with PTSD severity, and state dissociation and PTSD group made significant contributions to predicting perceptual priming for trauma words. The findings shed light on the importance of state dissociation in trauma-related information processing and posttraumatic symptoms.     

Serial processing in melody identification and the organization of musical semantic memory

Unlike the visual stimuli used in most object identification experiments, melodies are organized temporally rather than spatially. Therefore, they may be particularly sensitive to manipulations of the order in which information is revealed. Two experiments examined whether the initial elements of a melody are differentially important for identification. Initial exposures to impoverished versions of a melody significantly decreased subsequent identification, especially when the early exposures did not include the initial notes of the melody. Analyses of the initial notes indicated that they are differentially important for melody identification because they help the listener detect the overall structure of the melody. Confusion errors tended to be songs that either were drawn from the same genre or shared similar phrasing. These data indicate that conceptual processing influences melody identification, that phrase-level information is used to organize melodies in semantic memory, and that phrase-level information is required to effectively search semantic memory.     

Conceptual and perceptual memory: retrieval orientations reflected in event-related potentials

In memory retrieval, search can be guided by mental sets towards different subsets of the available evidence. Such retrieval orientations have been suggested to leave an imprint on event-related potentials (ERPs). The present study aimed at characterizing orientations towards perceptual and conceptual evidence in a recognition task, where pictures and words were studied. In the recognition test, items were presented in either the same format as at study or in the opposite format. A between-subjects manipulation modified the task, instructing an Exclusion group to endorse only items that preserved their format from study, and an Inclusion group to endorse both formats of a studied item. It was hypothesized that exclusion instructions would instill a perceptual and inclusion instructions a conceptual orientation. As a corollary, instructions were expected to dissociate the high end from the low end of the picture-word mirror effect. This expectation was confirmed in a behavioural experiment. In an ERP experiment, retrieval orientations were examined in their effects on correct rejections of new pictures and words. Confirming earlier findings [Hornberger, M., Morcom, A. M., & Rugg, M. D. (2004). Neural correlates of retrieval orientation: effects of study-test similarity. Journal of Cognitive Neuroscience, 16(7), 1196-1210], a perceptual orientation was accompanied by more positive-going amplitudes over widespread areas. The difference was larger for pictures than for words, supporting behavioural evidence that new pictures are more easily rejected on perceptual grounds than are new words. The Exclusion group showed no ERP evidence of cross-format old-new effects, despite reaction times indicative of involuntary conceptual recognition. The results indicate that perceptual and conceptual retrieval orientations imprint distinct signatures on ERPs. They further suggest that the examined old-new effects in ERPs are mainly linked to voluntary aspects of memory, even in a task where involuntary memory exerts effects on reaction times.     

Pseudoneglect: evidence for both perceptual and attentional factors

When neurologically normal individuals bisect a horizontal line as accurately as possible, they reliably show a slight leftward error. This leftward inaccuracy is called pseudoneglect because errors made by neurologically normal individuals are directionally opposite to those made by persons with visuospatial neglect (Jewell & McCourt, 2000). In the current study, normal right-handed observers bisected horizontal lines that were altered to bias line length judgments either toward the right or the left side of the line. Non-target dots were placed on or near the line stimuli using principles derived from a theory of visual illusions of length called centroid extraction (Morgan, Hole, & Glennerster, 1990). This theory argues that the position of a visual target is calculated as the mean position of all stimuli in close proximity to the target stimulus. We predicted that perceptual alterations that shifted the direction of centroid extraction would also shift the direction of line bisection errors. Our findings confirmed this prediction and support the idea that both perceptual and attentional factors contribute to the pseudoneglect effect.     

Conceptual information on objects' locations

According to traditional views, basic and subordinate concepts elicit perceptual information, superordinate concepts abstract information. Two experiments showed that also superordinate concepts activate perceptual and contextual information. In Experiment 1 participants evaluated the adequacy of Scene- and Object-like locations ascribed to basic and superordinate concepts. Superordinate concepts were judged faster when paired with Scene-like locations, where many exemplars can coexist, than with Object-like locations. The results were replicated and extended in the second experiment with a location production task. Theoretical accounts for the results are discussed.     

The mnemonic value of perceptual identification

In four experiments, subjects were required to name words presented on a CRT screen. On generate trials, the words were presented quickly, at a point where roughly half could be identified correctly; on read trials, the items were presented for a full second, allowing for rapid and easy naming. A surprise recognition test for the presented items then revealed a substantial retention advantage for the briefly presented items, but no similar advantage was produced in a recall. It is argued that under rapid viewing conditions subjects may fail to extract enough visual features to allow for immediate resolution, requiring the initiation of a kind of data-driven generation process. This latter process then produces a generation effect for the briefly presented items compared with the read items, but only on a retention test that shows sensitivity to data-driven processing. These results are discussed from the standpoint of current theoretical views on the generation effect.     

Temporal preparation facilitates perceptual identification of letters

Recent evidence has suggested that perceptual processing of single stimulus features improves when participants are temporally prepared for the occurrence of the stimuli. This study was conducted to investigate whether the benefit of temporal preparation generalizes to perceptual identification of more complex stimuli, such as letters. In three experiments, participants discriminated masked letters under high- and low-temporal-preparation conditions. Visual discrimination performance in all experiments improved when the participants were temporally prepared. Therefore, the present results support the notion that perception benefits from temporal preparation not only at the feature level, but also at subsequent levels at which feature information is integrated.     

Breaking the rules in perceptual information integration

We develop a broad theoretical framework for modelling difficult perceptual information integration tasks under different decision rules. The framework allows us to compare coactive architectures, which combine information before it enters the decision process, with parallel architectures, where logical rules combine independent decisions made about each perceptual source. For both architectures we test the novel hypothesis that participants break the decision rules on some trials, making a response based on only one stimulus even though task instructions require them to consider both. Our models take account of not only the decisions made but also the distribution of the time that it takes to make them, providing an account of speed-accuracy tradeoffs and response biases occurring when one response is required more often than another. We also test a second novel hypothesis, that the nature of the decision rule changes the evidence on which choices are based. We apply the models to data from a perceptual integration task with near threshold stimuli under two different decision rules. The coactive architecture was clearly rejected in favor of logical-rules. The logical-rule models were shown to provide an accurate account of all aspects of the data, but only when they allow for response bias and the possibility for subjects to break those rules. We discuss how our framework can be applied more broadly, and its relationship to Townsend and Nozawa’s (1995) Systems-Factorial Technology.     

Integration of perceptual information in word access

According to experiential theories of language comprehension, perceptual information plays an essential role when word meanings are accessed. We conducted four experiments to investigate how different types of perceptual information such as colour and shape are combined during word access. One possibility is that the colour and shape of a word's referent are activated independently from one another and are combined in an additive manner. Alternatively, words might activate perceptual representations via a multiplicative integration of colour and shape. Experiment 1 established that participants follow a multiplicative similarity rule when they judge the similarity of schematic pictures to actual fruits and vegetables. In Experiments 2 to 4, participants performed a classification task, a lexical decision task, or a word-naming task on names of fruits and vegetables that were superimposed on a background picture. Responses were facilitated only when both colour and shape of the picture matched the word's referents. Response times were associated negatively with mean similarity ratings and the consistency of these ratings obtained in the first experiment. These results suggest a multiplicative integration of different types of perceptual information during word access.     

A note on response-decision in perceptual identification

Summary Perceptual identification is conceived here as a two-stage process which includes perceptual processing and a response-decision. Three models for the decision part are discussed. Nakatani's (1972) model is based on choice theory and incorporates sophisticated guessing. Rumelhart's (1971) model assumes that the probability of a response equals either the prior or posterior probability of the stimulus corresponding to this response. A third model is derived which incorporates assumptions from both Nakatani's and Rumelhart's model. According to the results of two visual identification experiments Rumelhart's model has been rendered implausible whereas the third model provides a more plausible interpretation of the results.     

Mechanisms of facilitation in primed perceptual identification

We investigated the mechanism that produces priming in perceptual identification. In Experiment 1, subjects studied a series of compound words (e.g.,outdoor,sideline); in Experiment 2, subjects studied a series of pictures (photographs) of objects. All subjects later received perceptual identification tests in which old (primed) and new (unprimed) words (Experiment 1) or pictures (Experiment 2) were presented for varying durations and masked. In both experiments, performance for primed and unprimed stimuli was predicted essentially perfectly by a model that assumes that prior exposure to a stimulus results in increased visual information-acquisition rate when it is subsequently encountered. An ancillary purpose of Experiment 1 was to test whether or not priming occurs for recombined words (e.g.,outline); there was no evidence for such priming at any exposure duration.     

Conservation of temporal information by perceptual systems

Experiments in the auditory, visual, and vibratory modality employed two brief discriminably different stimuli, which were presented with temporal asynchronies unequivocally below the Hirsh-Sherrick threshold for performing temporal order judgments. A pair of such stimuli, experienced as a unitary perceptual event, is referred to as a “micropattern” composed of two “stimulus elements.” Ss could readily distinguish between two such micropatterns in which the temporal order of the stimulus elements was reversed. The discrimination was based on the perceptual dominance of the second stimulus element of each micropattern. This perceptual dominance was studied as a function of stimulus-element onset and offset asynchrony, the duration and intensity of the stimulus elements, and the difference (in frequency or wavelength) between the stimulus elements of a micropattern. The results suggest the existence of an operation of all perceptual systems in the time domain that acts to conserve information concerning the temporal order of the two stimulus elements at the expense of discriminatory acuity of the f’~rst element.