Repetition and the SNARC effect with one- and two-digit numbers.

The SNARC (Spatial Numerical Association of Response Codes) effect is the finding that small numbers elicit faster left than right responses and large numbers elicit faster right than left responses. This effect suggests that numbers activate left-right magnitude-laterality codes and that these codes interact with the selection of left-right responses. In the present research, subjects made parity decisions for one-digit numbers (in Experiment 1) and two-digit numbers (in Experiment 2), and we examined the effect of stimulus repetition on the SNARC effect. With single-digit stimuli, responses were faster and the SNARC effect was eliminated when stimuli were identical on successive trials. With two-digit stimuli, responses were faster when the ones digit was repeated, but the SNARC effect was found regardless of whether the digit was repeated or not. We argue that magnitude-laterality codes are activated in the process of accessing number information in memory and that this process can be short circuited if the visual stimulus matches that on the previous trial. Thus, no SNARC effect is found in Experiment 1 when identical stimuli are presented on successive trials. However, this result is not found in Experiment 2 because successive stimuli do not match even if the ones digit is repeated. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Memory scanning: Are fixed and varied sets scanned concurrently or successively?

Subjects were timed as they decided whether individually presented probe letters were or were not contained in pairs of memorized sets of one, two, or four letters. One set was fixed in advance of a block of trials, while the other varied from trial to trial. In Experiments 1 and 2, subjects responded positively if the probe was in either set and negatively otherwise; in Experiment 3 they made different responses to fixed-set, varied-set, and negative probes. In all three experiments, reaction time (RT) to varied-set probes depended more on the size of the varied set than of the fixed set, whereas RT to fixed-set and negative probes depended more on the size of the fixed set. These results were generally consistent with the hypothesis that scanning of the two sets was at least to some extent concurrent rather than successive, with the fixed set scanned more slowly than the varied set. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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. Ss performed recognition judgments on each of 2 words that followed each other by 0, 250, and 1,000 msec (Experiment 1) or 0 and 300 msec (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 lst 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 l; 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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The effect of grammatical gender on object categorization.

In 3 experiments, we investigated the effect of grammatical gender on object categorization. Participants were asked to judge whether 2 objects, whose names did or did not share grammatical gender, belonged to the same semantic category by pressing a key. Monolingual speakers of English (Experiment 1), Italian (Experiments 1 and 2), and Spanish (Experiments 2 and 3) were tested in their native language. Italian and Spanish participants responded faster to pairs of stimuli sharing the same gender, whereas no difference was observed for English participants. In Experiment 2, the pictures were chosen in such a way that the grammatical gender of the names was opposite in Italian and Spanish. Therefore, the same pair of stimuli gave rise to different patterns depending on the gender congruency of the names in the languages. In Experiment 3, Spanish speakers performed the same task under an articulatory suppression condition, showing no grammatical gender effect. The locus where meaning and gender interact can be located at the level of the lexical representation that specifies syntactic information: Nouns sharing the same grammatical gender activate each other, thus facilitating their processing and speeding up responses, either to semantically related pairs or to semantically unrelated pairs. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Recognition memory for new associations: electrophysiological evidence for the role of recollection

The electrophysiological correlates of recognition memory for new associations were investigated in two experiments. In both experiments subjects first studied unrelated word pairs. At test, they were presented with old words in the same pairing as at study (same pairs), old words in a different pairing from study (rearranged pairs), and pairs of new words. In Experiment 1 the test requirement was to discriminate between old and new pairs and, for any pair judged old, to then judge whether the pair was the same or rearranged. In Experiment 2 the requirement was merely to discriminate between old and new pairs. Event-related potentials (ERPs) were recorded for correctly classified same, rearranged and new pairs. The ERPs elicited by same pairs exhibited a similar pattern of effects in both experiments. Relative to the ERPs to new pairs, these effects took the form of sustained positive shifts with two distinct scalp maxima, over the left temporo-parietal and right frontal scalp respectively. ERPs to rearranged pairs showed effects which were similar in scalp topography, but markedly smaller in magnitude. This pattern of ERP effects closely resembles that found previously for test items defined as recollected on the basis of their attracting a successful source judgement. The findings therefore suggest that associative recognition memory shares some of the recollective processes that are engaged by the requirement to retrieve contextual information about a study episode. The findings from Experiment 2 indicate that the processes associated with the recollection of associated pairs are engaged regardless of whether the retrieval of associative information is an explicit task requirement.     

Hindsight bias and the misinformation effect: separating blended recollections from other recollection types

Questioning the presence of "truly" blended recollections, we investigated two cognitive phenomena: hindsight bias and the misinformation effect. At first glance, both phenomena seem to result from the same interference process, whereby the subsequent encoding of conflicting information impairs the recall of earlier encoded (original) material. Experiment 1 compared both paradigms using numerical items as material: hindsight as well as misinformation subjects revealed the same mean shift in their recollection of the original values. The additional analysis of a multinomial model, however, suggested that blended recollections occurred in the hindsight condition only. The misinformation effect, on the other hand, appeared to be based on averaging across two different recollection types. Experiment 2 further investigated how the memory-trace strength influences the likelihood for blended recollections to occur. In a misinformation procedure, one group of subjects read the original information twice, another group thrice. Again, recollections were similarly shifted towards the misinformation in both groups. But the multinomial model revealed that only the second group (with a stronger memory representation of the original information) showed blended recollections. Taken together, these results suggested that: (1) a minimum memory-trace strength of the original information must be met for blended recollections to occur; and (2) hindsight bias and the misinformation effect--though superficially similar--are induced by different cognitive processes.     

Effects of same-category and different-category extraneous memory sets on item recognition

In a study designed to distinguish between parallel and serial models of performance on Sternberg's item recognition task, Krueger (1975) presented subjects with a memory set (the "added" set) followed by a second ("core") set, a probe to the core set, and finally a probe to the added set. Response latency (RT) to both the core- and added-set probes initially increased with the size of the extraneous set. Over successive blocks of trials, the effect of the size of the extraneous set diminished. In Experiment 1 of the present study, Krueger's basic procedures were replicated with results similar to those he reported for early trials. Experiment 2 was a variation on the added-set procedure. Rather than the memory sets' being drawn from different categories (letters and digits), both sets consisted of digits. On half of the negative trials for both the core and the added tasks, the probe was drawn from the extraneous set, forcing the subjects to separate the two sets. Although RT on the core task did not increase with the size of the added set, there was an increase in RT to the added set with increases in core-set size, a finding inconsistent with the serial search model.     

Dimension-specific intertrial priming effects are task-specific: Evidence for multiple weighting systems.

Feature singleton search is faster when the target-defining dimension repeats across consecutive trials than when it changes (Found & Müller, 1996). However, this dimension repetition benefit (DRB) has also been demonstrated for the tasks with no search component (Mortier, Theeuwes, & Starreveld, 2005). If DRBs in the search and non-search tasks have the same origin, significant DRBs across trials of different tasks should rise. Two different tasks varied either in a predictable manner (Experiment 1) or randomly (Experiment 2) across trials. In detection task, search displays containing either color or orientation singletons were used. Discrimination task required identification of either color or orientation of a single presented item (non-search display). In Experiment 3, participants performed only the discrimination task, while the search and non-search displays varied randomly. There were significant DRBs for both tasks when the task repeated but not when the task changed (Experiments 1 and 2). DRBs were significant both when the display type repeated and when it changed (Experiment 3). Overall, the findings can be well explained by assuming multiple, independent dimension-weighting systems generating DRBs in different tasks. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Improving memory after interruption: Exploiting soft constraints and manipulating information access cost.

Forgetting what one was doing prior to interruption is an everyday problem. The recent soft constraints hypothesis (Gray, Sims, Fu, & Schoelles, 2006) emphasizes the strategic adaptation of information processing strategy to the task environment. It predicts that increasing information access cost (IAC: the time, and physical and mental effort involved in accessing information) encourages a more memory-intensive strategy. Like interruptions, access costs are also intrinsic to most work environments, such as when opening documents and e-mails. Three experiments investigated whether increasing IAC during a simple copying task can be an effective method for reducing forgetting following interruption. IAC was designated Low (all information permanently visible), Medium (a mouse movement to uncover target information), or High (an additional few seconds to uncover such information). Experiment 1 found that recall improved across all three levels of IAC. Subsequent experiments found that High IAC facilitated resumption after interruption, particularly when interruption occurred on half of all trials (Experiment 2), and improved prospective memory following two different interrupting tasks, even when one involved the disruptive effect of using the same type of resource as the primary task (Experiment 3). The improvement of memory after interruption with increased IAC supports the prediction of the soft constraints hypothesis. The main disadvantage of a high access cost was a reduction in speed of task completion. The practicality of manipulating IAC as a design method for inducing a memory-intensive strategy to protect against forgetting is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relational matching in baboons (Papio papio) with reduced grouping requirements.

Analogical reasoning is a corner stone of human cognition, but the phylogenetic origins of this skill are still unknown. Recent animal studies have suggested that only apes can solve the 2- by 2-item relational matching (RMTS) analogy problem, with potential benefits of language- (Premack, 1983) or token-training procedures (Thompson, Oden, & Boysen, 1997). In this study, 6 baboons were initially trained in an RMTS task in which the same and different relations were exemplified by compound stimuli made of 2 adjacent patches of colors. Learning occurred in this task with a first set of colors and transferred to probe trials with new colors (Experiment 1). Manipulation of the size of the sample or comparison stimuli (Experiment 2) showed that the performance was not merely controlled by the surface of the color patches, suggesting cognitive flexibility. Performance collapsed to chance level when a gap was introduced between the 2 elemental features composing the same or different displays (Experiment 3). Nevertheless, this effect of gap size was abolished by training (Experiment 4). It is suggested that monkeys share the ability to judge relations between relations with humans and apes, even in the absence of language or token training. However, this ability has been previously masked by a local mode of processing that hinders the processing of the stimuli as pairs rather than as independent objects. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Representation of serial order in pigeons (Columba livia).

In Experiment 1, 2 groups of pigeons were trained to respond to either a 4-item (A→B→C→D) or 5-item (A→B→C→D→E) list. After learning their respective list, half of the subjects were trained on a positive pair with reinforcement provided when pairs were responded to in the order true to that of the original sequence (4-item: B→C; 5-item: B→D). The remaining subjects were trained on a negative pair with reinforcement provided for responding to the pairs in the order opposite to that learned in the original sequence (4-item: C→B; 5-item: D→B). Subjects in the positive pair condition learned their respective pair faster than did subjects in the negative pair condition. In Experiment 2, after reaching criterion on a 4-item list, subjects received 16 BC probe trials spread across 4 sessions of training. Subjects performed significantly above chance on the probe trials. The performance of our subjects in Experiments 1 and 2 demonstrates that, similar to monkeys, pigeons form a representation of the lists that they learn. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of structural and naming factors of letters upon the recognition of tachistoscopic letters (author''s transl)

To determine the nature of effects of a preceding letter stimulus upon the recognition of a following letter stimulus, 20 subjects were sequentially and tachistoscopically presented pairs of letters of pairs of random patterns, which consist of the same number of elements, and asked to judge whether they were "same" or "different" in form. Four variable interstimulus intervals (ISI) between the 1st stimuli and the 2nd stimuli were employed as parameters. Results obtained were as follows: (a) percentages of correct responses for the letters were not significantly different from those for the random patterns, and (b) percentages of correct responses for the "same" matching tasks were significantly higher than those for the "different" matching tasks, but, differences in number of correct responses between the two tasks diminished as ISI increased. These results reveal structural, rather than naming, effects of preceding letters in the information processing of matching single letters.     

Selective attention and the suppression of cognitive noise.

The distractor-suppression effect is the relative slowing of Stroop (1935) color naming when the current appropriate response is identical to the inappropriate response activated by the distractor word appearing in the immediately preceding trial. Two experiments investigated aspects of the time course of distractor suppression. Experiment 1 found the suppression effect when subjects were instructed to maintain strict accuracy but not when subjects were encouraged to sacrifice some accuracy for greater speed. Experiment 2 traced the recovery from suppression by varying the interval between successive trials (20, 520, 1020, or 2020 ms). The suppression effect was found to persist for at least a second; by 2 s the effect was completely dissipated. The results support the view of selective inhibition as an active, time-dependent control process that develops over time following the activation of distracting information and that it is released after response to the task-appropriate information has been made. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Time, capacity, and selection between perceptual attributes

Three experiments were run to determine whether time and central-processing capacity are requried to select between perceptual attributes. A same-different matching task was employed for all experiments. In Experiments 1 and 2, three sets of stimulus pairs were used, each of which varied along only one relevant perceptual dimension (color, size, or form). In Experiment 1, reaction time on the matching task was shown to be faster when the stimuli were presented in blocks in which all stimulus pairs came from the same set (blocked presentation) than when stimulus pairs from each of the three sets were randomly intermixed (random presentation). In Experiment 2, reaction time on a secondary probe task was faster during the encoding stage of a sequential mathcing task with blocked presentation than with random presentation. Experiment 3 indicated that this outcome could not be attributed to a difference in the number of possible stimulus alternatives. Thus, the results support the hypothesis that time and central-processing capacity are required to select between perceptual attributes.     

Prototypes and particulars: Geometric and experience-dependent spatial categories.

People use geometric cues to form spatial categories. This study investigated whether people also use the spatial distribution of exemplars. Adults pointed to remembered locations on a tabletop. In Experiment 1, a target was placed in each geometric category, and the location of targets was varied. Adults' responses were biased away from a midline category boundary toward geometric prototypes located at the centers of left and right categories. Experiment 2 showed that prototype effects were not influenced by cross-category interactions. In Experiment 3, subsets of targets were positioned at different locations within each category. When prototype effects were removed, there was a bias toward the center of the exemplar distribution, suggesting that common categorization processes operate across spatial and object domains. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The learning of generalized motor programs: Reducing the relative frequency of knowledge of results enhances memory.

In earlier studies, reducing the relative frequency of knowledge of results (KR) enhanced retention of single movements. In the experiments here we asked whether this variable also enhances memory for classes of actions governed by generalized motor programs. Acquisition conditions involved practicing three versions of a sequential timing task. All three versions had the same temporal structure (or phasing), but the overall durations were different. KR was presented on either 100% or 67% of the trials for two groups. In Experiment 1, reduced relative KR frequency, spread equally across all task versions, enhanced accuracy of the learned relative timing structure as measured on a transfer test with a novel movement duration. Experiment 2 showed that retention of a medium-duration version was more accurate for subjects who never received KR about it in acquisition, as compared with subjects who always did. The data support the view that reduced KR frequency enhances acquisition of the relative-timing structure underlying memory for a class of actions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Echo suppression and discrimination suppression aspects of the precedence effect

The precedence effect is a phenomenon that may occur when a sound from one direction (the lead) is followed within a few milliseconds by the same or a similar sound from another direction (the lag, or the echo). Typically, the lag sound is not heard as a separate event, and changes in the lag sound's direction cannot be discriminated. The hypothesis is proposed in this study that these two aspects of precedence (echo suppression and discrimination suppression) are at least partially independent phenomena. Two experiments were conducted in which pairs of noise bursts were presented to subjects from two loudspeakers in the horizontal plane to simulate a lead sound and a lag sound (the echo). Echo suppression threshold was measured as the minimum echo delay at which subjects reported hearing two sounds rather than one sound; discrimination suppression threshold was measured as the minimum echo delay at which subjects could reliably discriminate between two positions of the echo. In Experiment 1, it was found that echo suppression threshold was the same as discrimination suppression threshold when measured with a single burst pair (average 5.4 msec). However, when measured after presentation of a train of burst pairs (a condition that may produce "buildup of suppression"), discrimination suppression threshold increased to 10.4 msec, while echo suppression threshold increased to 26.4 msec. The greater buildup of echo suppression than of discrimination suppression indicates that the two phenomena are distinct under buildup conditions and may be the reflection of different underlying mechanisms. Experiment 2 investigated the effect of the directional properties of the lead and lag sounds on discrimination suppression and echo suppression. There was no consistent effect of the spatial separation between lead and lag sources on discrimination suppression or echo suppression, nor was there any consistent difference between the two types of thresholds (overall average threshold was 5.9 msec). The negative result in Experiment 2 may have been due to the measurements being obtained only for single-stimulus conditions and not for buildup conditions that may involve more central processing by the auditory system.     

False recognition of abstract versus common objects in older and younger adults: Testing the semantic categorization account.

Older adults often demonstrate higher levels of false recognition than do younger adults. However, in experiments using novel shapes without preexisting semantic representations, this age-related elevation in false recognition was found to be greatly attenuated. Two experiments tested a semantic categorization account of these findings, examining whether older adults show especially heightened false recognition if the stimuli have preexisting semantic representations, such that semantic category information attenuates or truncates the encoding or retrieval of item-specific perceptual information. In Experiment 1, ambiguous shapes were presented with or without disambiguating semantic labels. Older adults showed higher false recognition when labels were present but not when labels were never presented. In Experiment 2, older adults showed higher false recognition for concrete but not abstract objects. The semantic categorization account was supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Chromatin structure and the expression of cardiac genes

Three experiments investigated visual search for singleton feature targets. The critical dimension on which the target differed from the nontargets was either known in advance or unknown--that is, the critical difference varied either within a dimension or across dimensions. Previous work (Treisman, 1988) had shown that, while the search reaction time (RT) functions were flat in both conditions, there was an intercept cost for the cross-dimension condition. Experiment 1 examined whether this cost would disappear when responses could be based on the detection of any (target-nontarget) difference in the display (by requiring a "heterogeneity/homogeneity" decision). The cost remained. This argues that pop-out requires (or involves) knowledge of the particular dimension in which an odd-one-out target differs from the nontargets; furthermore, that knowledge is acquired through the elimination of dimensions not containing a target. In Experiment 2, the subjects had to eliminate (or ignore) one potential source of difference in order to give a positive response (displays could contain a "noncritical" difference requiring a negative response). The result was a comparatively large cost in the within-dimension (positive) condition. This can be taken to indicate that pop-out as such does not make available information as to the particular feature value in which the target differs from the nontargets. Experiment 3 examined whether search priorities can be biased in accordance with advance knowledge of the likely source of difference. The subjects were found to have a high degree of top-down control over what particular dimension to assign priority of checking to. The implication of the results for models of visual search and selection are discussed.     

Backward inhibitory conditioning with signaled and unsignaled unconditioned stimuli: Distribution of trials across days and intertrial interval.

Through summation tests in conditioned suppression with rats we assessed the effects of distribution of trials across days (Experiment 1) and intertrial interval (ITI) (Experiment 2) on the degree of backward conditioned inhibition established through signaled and unsignaled unconditioned stimuli (USs). Two backward conditioned inhibitory stimuli (CS-s) were established within subjects: One backward CS- followed signaled shocks; the other followed unsignaled shocks. After 12 daily sessions (Experiment 1), the signaled backward CS- was strongly inhibitory and significantly more inhibitory than the unsignaled backward CS-. When the same number of trials occurred in a single long session, performances to both CS-s converged at moderate levels. At the 90-s ITI, (Experiment 2) the signaled and unsignaled backward CS-s were nearly equivalent in effectiveness. When the ITI was 540 s, performances diverged, and signaled backward CS- was substantially more effective; the longer ITI facilitated inhibitory backward conditioning based upon signaled USs but prevented the development of inhibitory backward conditioning based upon unsignaled USs. These functionally opposite effects on backward conditioned inhibition, depending on whether the US was signaled or not, are anticipated by Wagner's "standard operating procedure" (SOP) model of short-term memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)