Effects of color on perceptual and conceptual tests of implicit memory

Two experiments are reported that explore why recent investigations of implicit memory failed to find any effects of color information on test performance. In the first experiment, participants studied colored pictures as well as words printed in colored ink without any memory instructions. During the test phase, a verbal and a pictorial version of a color-choice task (a conceptual priming test) were compared to two perceptual tests (word-stem completion and picture-fragment identification). Similar and significant amounts of priming to color occurred in both color-choice tasks. The perceptual tests were found to be sensitive to changes in the stimulus-presentation mode from study to test, but stimuli remaining the same color and those changed to black-and-white did not differ in the priming scores. In the second experiment, a mild division of attention was introduced in the study phase. Once again, priming to color was observed only in the verbal version of a color-choice test and not in the word-stem completion test. Dividing attention did not decrease performance on both implicit tests, whereas an explicit test of color recall for studied pictures suffered from dividing attention at encoding. It is concluded that a perceptual attribute such as color may be represented and coded by conceptual processing. Furthermore, automatic (or not attention-demanding) encoding processes may suffice for later conceptual tests of implicit memory. Previous failures to find any effects of color information on implicit performance are attributed to the use of perceptual priming tests. Received: 30 June 1997 / Accepted: 20 April 1998     

How "implicit" are implicit color effects in memory?

Processing colored pictures of objects results in a preference to choose the former color for a specific object in a subsequent color choice test (Wippich & Mecklenbr?uker, 1998). We tested whether this implicit memory effect is independent of performances in episodic color recollection (recognition). In the study phase of Experiment 1, the color of line drawings was either named or its appropriateness was judged. We found only weak implicit memory effects for categorical color information. In Experiment 2, silhouettes were colored by subjects during the study phase. Performances in both the implicit and the explicit test were good. Selections of "old" colors in the implicit test, though, were almost completely confined to items for which the color was also remembered explicitly. In Experiment 3, we applied the opposition technique in order to check whether we could find any implicit effects regarding items for which no explicit color recollection was possible. This was not the case. We therefore draw the conclusion that implicit color preference effects are not independent of explicit recollection, and that they are probably based on the same episodic memory traces that are used in explicit tests.     

Priming on verbal perceptual tests: Roles of lexical,surface, and conceptual processes

According to a lexical-access hypothesis, priming on verbal-completion tests requires previous access to higher-order nodes such as morphemes or words. In two experiments, subjects studied words presented in printed color, either by reading the words or by naming the printed colors. In Experiment 2, some of the words were to be ignored in both study conditions. The words presented in Experiment 2 were either conceptually related or unrelated to each other. And the cues in the test phase for repeated targets were either printed in the studied color or in a different color. In both experiments, the word stems of nouns studied and of new targets were presented with word-completion instructions (implicit test of memory). Consistent with the hypothesis, the amount of priming obtained was greater in the reading than in the color-naming condition. The least amount of priming was observed for targets that were to be ignored at study. In addition, Experiment 2 showed considerable effects of surface similarity (i.e., stronger priming effects with cues whose color was not changed from the study to the test phase) and some effects of conceptual processing, as was indicated by different amounts of priming for unrelated and for related nouns. Because these two effects were observed with both types of study task, it is concluded that perceptual and conceptual processes may make independent contributions to priming effects in verbal perceptual tests. This conclusion modifies and extends the original hypothesis, according to which previous lexical access is required in order to obtain effects of perceptual or conceptual processes on the priming scores.     

Implicit memory for textual materials

As a word moves from isolation in a list to being contextually bound in meaningful discourse, its probability of priming in tests of implicit memory decreases. The present experiments explore whether considerable priming effects can be revealed with conceptual tests of implicit memory as compared to perceptual tests. In the study phase, meaningful actions were described within a coherent text. In Experiment 1 subjects elaborated half of the actions by visual imagery. In Experiment 2, subjects elaborated the actions by enacting them symbolically. In both experiments, subjects in a control condition were simply required to read the same activities. In Experiment 2, a further group of subjects had to detect orthographic errors. The results demonstrated reliable effects of implicit memory in terms of associations with verbs repeated from the studied text. This form of repetition priming for textual materials in a conceptual test of implicit memory was enhanced by both types of elaboration. A word-stem completion task for the same targets revealed a less pronounced and inconsistent priming effect, uninfluenced by both types of elaboration. But the latter form of perceptual priming was found to be more pronounced within the error-detection condition. Measures of explicit memory showed similar effects of elaborative encoding conditions but there were some dissimilarities to measures of implicit memory, too. In general and in accordance with a transfer-appropriate processing view, conceptual tests rather than perceptual tests may be more suitable for detecting effects of implicit memory within the domain of text processing.     

Cross-modal priming and explicit memory in patients with verbal production deficits

Implicit memory is often thought to reflect an influence of past experience on perceptual processes, yet priming effects are found when the perceptual format of stimuli changes between study and test episodes. Such cross-modal priming effects have been hypothesized to depend upon stimulus recoding processes whereby a stimulus presented in one modality is converted to other perceptual formats. The present research examined recoding accounts of cross-modal priming by testing patients with verbal production deficits that presumably impair the conversion of visual words into auditory/phonological forms. The patients showed normal priming in a visual stem completion task following visual study (Experiment 1), but showed impairments following auditory study in both implicit (Experiment 2) and explicit (Experiment 3) stem completion. The results are consistent with the hypothesis that verbal production processes contribute to the recoding of visual stimuli and support cross-modal priming. The results also indicate that shared processes contribute to both explicit memory and cross-modal implicit memory.     

Component processes of conceptual priming and associative cued recall: the roles of preexisting representation and depth of processing

The authors investigated depth-of-processing effects on conceptual priming by comparing incidental (implicit) and intentional (explicit) tests of word association. In Experiment 1, depth of processing at study influenced priming of weak and medium associates but not of strong associates. In Experiment 2, depth of processing influenced priming of weak associates but not of compound phrases (e.g., coathanger), whose preexperimental association strength matched that of weak associates. In Experiment 3, the same pattern persisted when study was auditory and test was visual, ensuring that priming was conceptual and not perceptual. In all experiments, in matched intentional tests, depth-of-processing effects occurred for all association strengths and for both phrases and associates, suggesting that the incidental tests were uncontaminated by voluntary retrieval, because they showed depth-of-processing effects only for some materials and not others, within the same participants and tests. Because depth-of-processing effects on involuntary free-association priming depend on the presence versus absence of a cohesive preexperimental representation, the memory-systems and conceptual/perceptual processing approaches to memory-test dissociations require modification to account for component processes of conceptual priming.     

Influence of object size on baseline identification, priming, and explicit memory

We investigated the influence of size on identification, priming, and explicit memory for color photos of common objects. Participants studied objects displayed in small, medium, and large sizes and memory was assessed with both implicit identification and explicit recognition tests. Overall, large objects were easier to identify than small objects and study-to-test changes in object size impeded performance on explicit but not implicit memory tests. In contrast to previous findings with line-drawings of objects but consistent with predictions from the distance-as-filtering hypothesis, we found that study-test size manipulations had large effects on old/new recognition memory test for objects displayed in large size at test but not for objects displayed small or medium at test. Our findings add to the growing body of literature showing that the findings obtained using line-drawings of objects do not necessarily generalize to color photos of common objects. We discuss implications of our findings for theories of object perception, memory, and eyewitness identification accuracy for objects.     

Effects of hearing words, imaging hearing words, and reading on auditory implicit and explicit memory tests

In four experiments, we examined the degree to which imaging written words as spoken by a familiar talker differs from direct perception (hearing words spoken by that talker) and reading words (without imagery) on implicit and explicit tests. Subjects first performed a surface encoding task on spoken, imagined as spoken, or visually presented words, and then were given either an implicit test (perceptual identification or stem completion) or an explicit test (recognition or cued recall) involving auditorily presented words. Auditory presentation at study produced larger priming effects than did imaging or reading. Imaging and reading yielded priming effects of similar magnitude, whereas imaging produced lower performance than reading on the explicit test of cued recall. Voice changes between study and test weakened priming on the implicit tests, but did not affect performance on the explicit tests. Imagined voice changes affected priming only in the implicit task of stem completion. These findings show that the sensitivity of a memory test to perceptual information, either directly perceived or imagined, is an important dimension for dissociating incidental (implicit) and intentional (explicit) retrieval processes.     

Age differences in implicit memory: fragmented object identification and category exemplar generation.

In a cross-sectional study of 164 participants aged 21 to 91, the authors examined age differences on two implicit tests, fragmented object identification (FOI) and category exemplar generation (CEG), and on tests of explicit memory, attention, and verbal fluency. FOI results revealed impaired perceptual skill learning in those over 60 and a decrease in perceptual priming across young, middle-aged, and older groups. CEG priming was impaired in those over 80. Regression analysis revealed explicit contamination of priming on both the FOI and CEG tests. Across the three implicit measures, age accounted for 4 to 13% of the variance when explicit memory was controlled. Semantic fluency predicted CEG priming, suggesting possible frontal lobe involvement on the test. Altogether, results indicate that age has a small but reliable influence on implicit memory.     

Attention and perceptual implicit memory: effects of selective versus divided attention and number of visual objects

Extant research presents conflicting results on whether manipulations of attention during encoding affect perceptual priming. Two suggested mediating factors are type of manipulation (selective vs divided) and whether attention is manipulated across multiple objects or within a single object. Words printed in different colors (Experiment 1) or flanked by colored blocks (Experiment 2) were presented at encoding. In the full-attention condition, participants always read the word, in the unattended condition they always identified the color, and in the divided-attention conditions, participants attended to both word identity and color. Perceptual priming was assessed with perceptual identification and explicit memory with recognition. Relative to the full-attention condition, attending to color always reduced priming. Dividing attention between word identity and color, however, only disrupted priming when these attributes were presented as multiple objects (Experiment 2) but not when they were dimensions of a common object (Experiment 1). On the explicit test, manipulations of attention always affected recognition accuracy.     

提取干扰对知觉和概念启动的影响

通过学习—测验范式,分别以词汇判断、语义分类任务为测验,探讨提取干扰对不同识别式记忆的影响差异。结果发现,实验1验证了识别式知觉内隐记忆的提取干扰效应,实验2发现识别式概念内隐记忆在提取干扰下也明显降低;两个实验启动量联合分析发现,相比无干扰条件,概念启动比知觉启动受到提取干扰的破坏更大。上述结果说明识别式内隐记忆的提取干扰具有普遍性,提取干扰产生了不同识别式内隐记忆之间的分离,识别式概念内隐记忆更容易受到提取干扰的影响。     

Transfer between vision and haptics: Memory for 2-D patterns and 3-D objects

Explicit memory tests such as recognition typically access semantic, modality-independent representations, while perceptual implicit memory tests typically access presemantic, modality-specific representations. By demonstrating comparable cross- and within-modal priming using vision and haptics with verbal materials (Easton, Srinivas, & Greene, 1997), we recently questioned whether the representations underlying perceptual implicit tests were modality specific. Unlike vision and audition, with vision and haptics verbal information can be presented in geometric terms to both modalities. The present experiments extend this line of research by assessing implicit and explicit memory within and between vision and haptics in the nonverbal domain, using both 2-D patterns and 3-D objects. Implicit test results revealed robust cross-modal priming for both 2-D patterns and 3-D objects, indicating that vision and haptics shared abstract representations of object shape and structure. Explicit test results for 3-D objects revealed modality specificity, indicating that the recognition system keeps track of the modality through which an object is experienced.     

Direct comparison of auditory implicit memory tests

In this experiment, we examined the degree to which four implicit tests and two explicit tests, all involving auditory presentation, were sensitive to the perceptual characteristics of the stimuli presented during study. Presenting stimuli visually decreased priming in all the implicit memory tests, relative to auditory presentation. However, changing voice between study and test decreased priming only in the implicit memory tests requiring identification of words degraded by noise or by low-pass filtering, but not in those tests requiring generation from word portions (stems and fragments). Modality effects without voice effects were observed in cued recall, but the opposite pattern of results (voice effects without modality effects) was obtained in recognition. The primary new finding is the demonstration that auditory memory tests, both explicit and implicit, differ in their sensitivity to the perceptual information encoded during study.     

On associations between computers and restaurants: Rapid learning of new associations on a conceptual implicit memory test

A novel event-based conceptual implicit memory test was designed to tap the development of new associations between objects and ad hoc categories. At study, participants were presented with a plausible story that linked an incongruous object (computer) with an ad hoc category (restaurant). At test, participants judged whether a given object was typically found in a restaurant. In Experiment 1, judgment time was significantly slower for the incongruous object (computer) when the story had previously linked the computer to the restaurant, relative to when it had not. Experiment 2 replicated this effect and ruled out the alternative interpretation that this interference effect was attributable to a general slowing of responses to all studied items. Unlike in prior studies, this demonstration of associative priming cannot be attributed to perceptual priming or to test awareness in memory-intact participants. The paradigm therefore offers a unique opportunity to study single-trial conceptual learning in memory-intact and memory-impaired populations.     

Different involuntary mechanisms underlie priming and LOP effects in stem completion tests

The role of intentional retrieval, involuntary conscious memory, and lexical processing in priming and levels-of-processing (LOP) effects in stem completion tests was investigated in three experiments. First, Experiment 1 provided strong evidence against the intentional retrieval hypothesis for the implicit LOP effects. LOP effects in the explicit test were dependent on intertrial interval at test, whereas LOP effects in the implicit test were not. Second, support was provided for the involuntary conscious memory hypothesis. Implicit memory (priming) was associated with awareness in all three experiments and the implicit LOP effect was associated with awareness in two of the three experiments. Third, it was concluded that lexical processing per se played a limited role in both priming and implicit LOP effects. Although priming was sensitive to normative rates of production in Experiment 1 and the number of solutions in all three experiments, it was insensitive to frequency manipulations. The LOP effect was insensitive to number of solutions, normative rates of production, and frequency manipulations. In addition, LOP and priming effects were uncorrelated in the implicit memory tests. It was concluded that production processes (e.g., Gabrieli et al., 1999), rather than lexical processes, played a crucial role in stem completion priming. In contrast, the LOP effect was attributed to the involuntary interaction of episodic and perceptual memory.     

Different involuntary mechanisms underlie priming and LOP effects in stem completion tests

The role of intentional retrieval, involuntary conscious memory, and lexical processing in priming and levels‐of‐processing (LOP) effects in stem completion tests was investigated in three experiments. First, Experiment 1 provided strong evidence against the intentional retrieval hypothesis for the implicit LOP effects. LOP effects in the explicit test were dependent on intertrial interval at test, whereas LOP effects in the implicit test were not. Second, support was provided for the involuntary conscious memory hypothesis. Implicit memory (priming) was associated with awareness in all three experiments and the implicit LOP effect was associated with awareness in two of the three experiments. Third, it was concluded that lexical processing per se played a limited role in both priming and implicit LOP effects. Although priming was sensitive to normative rates of production in Experiment 1 and the number of solutions in all three experiments, it was insensitive to frequency manipulations. The LOP effect was insensitive to number of solutions, normative rates of production, and frequency manipulations. In addition, LOP and priming effects were uncorrelated in the implicit memory tests. It was concluded that production processes (e.g., Gabrieli et al., 1999), rather than lexical processes, played a crucial role in stem completion priming. In contrast, the LOP effect was attributed to the involuntary interaction of episodic and perceptual memory.     

Midazolam amnesia and conceptual processing in implicit memory

Prominent theories of implicit memory (D. Schacter, B. Church, & J. Treadwell, 1994) emphasize the dominant role of perceptual processing in mediating priming on perceptual implicit memory tests. Examinations of the effects of conceptual processing on perceptual implicit memory tests have produced ambiguous results. Although a number of investigations (e.g., J. Toth & R. Hunt, 1990) have demonstrated that variations in conceptual processing affect priming on perceptual implicit memory tests, these effects may arise because of the contaminating effects of explicit memory. The current experiment examined this controversy using midazolam, a benzodiazepine that produces a dense, albeit temporary, anterograde amnesia when injected prior to study. The experiment examined whether the effects of generation found on the implicit memory test of perceptual identification were affected by a midazolam injection prior to study. Results demonstrated that midazolam substantially diminished generation effects in free and cued recall, as well as overall performance on these tests, but had no detectable effect on the generation effect in perceptual identification.     

An investigation of false memory in perceptual implicit tasks

Reports of critical lure priming in perceptual implicit tasks [e.g., McKone, E., & Murphy, B. (2000). Implicit false memory: Effects of modality and multiple study presentations on long-lived semantic priming. Journal of Memory and Language, 43, 89-109] using the Deese-Roediger-McDermott [Roediger, H. L., III, & McDermott, K. B. (1995). Creating false memories: Remembering words not presented in lists. Journal of Experimental Psychology: Learning, Memory, and Cognition, 21, 803-814] procedure have suggested availability of the lexical form of lure items at study. Three experiments were conducted to further explore "false" implicit priming in perceptual tests. In Experiments 1 and 3, implicit and explicit stem completion tests were given in the DRM procedure with semantic lists; in Experiment 2, a graphemic response test was used in a similar design. For all experiments, explicit instructions resulted in reliable false memory, while implicit instructions resulted in priming for list items and no priming for lure items. Priming for lure items was evident for "test-aware" subjects only in Experiment 1 and in a combined analysis for all three experiments. These results establish boundary conditions for priming for critical lures and indicate that access to the lexical form of critical lures may not occur under incidental learning conditions when strong controls against explicit retrieval are implemented.     

A mere exposure effect for transformed three-dimensional objects: Effects of reflection, size, or color changes on affect and recognition

If the mere exposure effect is based on implicit memory, recognition and affect judgments should be dissociated by experimental variables in the same manner as other explicit and implicit measures. Consistent with results from recognition and picture naming or object decision priming tasks (e.g., Biederman & E. E. Cooper, 1991, 1992; L. A. Cooper, Schacter, Ballesteros, & Moore, 1992), the present research showed that recognition memory but not affective preference was impaired by reflection or size transformations of three-dimensional objects between study and test. Stimulus color transformations had no effect on either measure. These results indicate that representations that support recognition memory code spatial information about an object’s left-right orientation and size, whereas representations that underlie affective preference do not. Insensitivity to surface feature changes that do not alter object form appears to be a general characteristic of implicit memory measures, including the affective preference task.     

Selective attention affects implicit and explicit memory for familiar pictures at different delay conditions

Three experiments investigated the effects of two variables -selective attention during encoding and delay between study and test- on implicit (picture fragment completion and object naming) and explicit (free recall and recognition) memory tests. Experiments 1 and 2 consistently indicated that (a) at all delays (immediate to 1 month), picture-fragment identification threshold was lower for the attended than the unattended pictures; (b) the attended pictures were recalled and recognized better than the unattended; and (c) attention and delay interacted in both memory tests. For implicit memory, performance decreased as delay increased for both attended and unattended pictures, but priming was more pronounced and lasted longer for the attended pictures; it was still present after a 1-month delay. For explicit memory, performance decreased as delay increased for attended pictures, but for unattended pictures performance was consistent throughout delay. By using a perceptual object naming task, Experiment 3 showed reliable implicit and explicit memory for attended but not for unattended pictures. This study indicates that picture repetition priming requires attention at the time of study and that neither delay nor attention dissociate performance in explicit and implicit memory tests; both types of memory require attention, but explicit memory does so to a larger degree.