Spatial interference between attended items engenders serial visual processing

A pair of experiments investigated the architecture of visual processing, parallel versus serial, across high and low levels of spatial interference in a divided attention task. Subjects made speeded judgments that required them to attend to a pair of color-cued objects among gray filler items, with the spatial proximity between the attended items varied to manipulate the strength of interference between attended items. Systems factorial analysis (Townsend & Nozawa, Journal of Mathematical Psychology 39:321-359, 1995) was used to identify processing architecture. Experiment 1, using moderately dense displays, found evidence of parallel processing whether attended objects were in low or high proximity to one another. Experiment 2, using higher-density displays, found evidence of parallel selection when attended stimuli were widely separated but serial processing when they were in high proximity. Divided visual attention can operate in parallel under conditions of low or moderate spatial interference between selected items, but strong interference engenders serial processing.     

Asymmetric binding in serial memory for verbal and spatial information

As the number of studies showing that items can be retained as bound representations in memory increases, researchers are beginning to investigate how the different features are bound together. In the present study, we examined the relative importances of the verbal and spatial features in serial memory for visual stimuli. Participants were asked to memorize the order of series of letters presented visually in different locations on the computer screen. The results showed that manipulating the phonological similarity of the letters affected recall of their spatial locations, but that increasing the complexity of the spatial pattern had no effect on recall of the letters. This finding was observed in both order reconstruction (Exps. 1 and 2) and probe serial recall (Exps. 3 and 4), suggesting that verbal–spatial binding in serial memory for visual information is asymmetric.     

Escaping the recent past: Which stimulus dimensions influence proactive interference?

Proactive interference occurs when information from the past disrupts current processing and is a major source of confusion and errors in short-term memory (STM; Wickens, Born, & Allen, Journal of Verbal Learning and Verbal Behavior, 2:440–445, 1963). The present investigation examines potential boundary conditions for interference, testing the hypothesis that potential competitors must be similar along task-relevant dimensions to influence proactive interference effects. We manipulated both the type of task being completed (Experiments 1, 2, and 3) and dimensions of similarity irrelevant to the current task (Experiments 4 and 5) to determine how the recent presentation of a probe item would affect the speed with which participants could reject that item. Experiments 1, 2, and 3 contrasted STM judgments, which require temporal information, with semantic and perceptual judgments, for which temporal information is irrelevant. In Experiments 4 and 5, task-irrelevant information (perceptual similarity) was manipulated within the recent probes task. We found that interference from past items affected STM task performance but did not affect performance in semantic or perceptual judgment tasks. Conversely, similarity along a nominally irrelevant perceptual dimension did not affect the magnitude of interference in STM tasks. Results are consistent with the view that items in STM are represented by noisy codes consisting of multiple dimensions and that interference occurs when items are similar to each other and, thus, compete along the dimensions relevant to target selection.     

A severe capacity limit in the consolidation of orientation information into visual short-term memory

Previous research has suggested that two color patches can be consolidated into visual short-term memory (VSTM) via an unlimited parallel process. Here we examined whether the same unlimited-capacity parallel process occurs for two oriented grating patches. Participants viewed two gratings that were presented briefly and masked. In blocks of trials, the gratings were presented either simultaneously or sequentially. In Experiments 1 and 2, the presentation of the stimuli was followed by a location cue that indicated the grating on which to base one’s response. In Experiment 1, participants responded whether the target grating was oriented clockwise or counterclockwise with respect to vertical. In Experiment 2, participants indicated whether the target grating was oriented along one of the cardinal directions (vertical or horizontal) or was obliquely oriented. Finally, in Experiment 3, the location cue was replaced with a third grating that appeared at fixation, and participants indicated whether either of the two test gratings matched this probe. Despite the fact that these responses required fairly coarse coding of the orientation information, across all methods of responding we found superior performance for sequential over simultaneous presentations. These findings suggest that the consolidation of oriented gratings into VSTM is severely limited in capacity and differs from the consolidation of color information.     

Enhanced visual short-term memory in action video game players

Visual short-term memory (VSTM) is critical for acquiring visual knowledge and shows marked individual variability. Previous work has illustrated a VSTM advantage among action video game players (Boot et al. Acta Psychologica 129:387–398, 2008). A growing body of literature has suggested that action video game playing can bolster visual cognitive abilities in a domain-general manner, including abilities related to visual attention and the speed of processing, providing some potential bases for this VSTM advantage. In the present study, we investigated the VSTM advantage among video game players and assessed whether enhanced processing speed can account for this advantage. Experiment 1, using simple colored stimuli, revealed that action video game players demonstrate a similar VSTM advantage over nongamers, regardless of whether they are given limited or ample time to encode items into memory. Experiment 2, using complex shapes as the stimuli to increase the processing demands of the task, replicated this VSTM advantage, irrespective of encoding duration. These findings are inconsistent with a speed-of-processing account of this advantage. An alternative, attentional account, grounded in the existing literature on the visuo-cognitive consequences of video game play, is discussed.     

Top-down constraint on recognition memory

Can recognition memory be constrained “at the front end,” such that people are more likely to retrieve information about studying a recognition-test probe from a specified target source than they are to retrieve such information about a probe from a nontarget source? We adapted a procedure developed by Jacoby, Shimizu, Daniels, and Rhodes (Psychonomic Bulletin & Review 12:852–857, 2005) to address this question. Experiment 1 yielded evidence of source-constrained retrieval, but that pattern was not significant in Experiments 2, 3, and 4 (nor in several unpublished pilot experiments). In Experiment 5, in which items from the two studied sources were perceptibly different, a pattern consistent with front-end constraint of recognition emerged, but this constraint was likely exercised via visual attention rather than memory. Experiment 6 replicated both the absence of a significant constrained-retrieval pattern when the sources did not differ perceptibly (as in Exps. 2, 3 and 4) and the presence of that pattern when they did differ perceptibly (as in Exp. 5). Our results suggest that people can easily constrain recognition when items from the to-be-recognized source differ perceptibly from items from other sources (presumably via visual attention), but that it is difficult to constrain retrieval solely on the basis of source memory.     

Coarse guidance by numerosity in visual search

In five experiments, we examined whether the number of items can guide visual focal attention. Observers searched for the target area with the largest (or smallest) number of dots (squares in Experiment 4 and “checkerboards” in Experiment 5) among distractor areas with a smaller (or larger) number of dots. Results of Experiments 1 and 2 show that search efficiency is determined by target to distractor dot ratios. In searches where target items contained more dots than did distractor items, ratios over 1.5:1 yielded efficient search. Searches for targets where target items contained fewer dots than distractor items were harder. Here, ratios needed to be lower than 1:2 to yield efficient search. When the areas of the dots and of the squares containing them were fixed, as they were in Experiments 1 and 2, dot density and total dot area increased as dot number increased. Experiment 3 removed the density and area cues by allowing dot size and total dot area to vary. This produced a marked decline in search performance. Efficient search now required ratios of above 3:1 or below 1:3. By using more realistic and isoluminant stimuli, Experiments 4 and 5 show that guidance by numerosity is fragile. As is found with other features that guide focal attention (e.g., color, orientation, size), the numerosity differences that are able to guide attention by bottom-up signals are much coarser than the differences that can be detected in attended stimuli.     

Explaining efficient search for conjunctions of motion and form: Evidence from negative color effects

Dent, Humphreys, and Braithwaite (2011) showed substantial costs to search when a moving target shared its color with a group of ignored static distractors. The present study further explored the conditions under which such costs to performance occur. Experiment 1 tested whether the negative color-sharing effect was specific to cases in which search showed a highly serial pattern. The results showed that the negative color-sharing effect persisted in the case of a target defined as a conjunction of movement and form, even when search was highly efficient. In Experiment 2, the ease with which participants could find an odd-colored target amongst a moving group was examined. Participants searched for a moving target amongst moving and stationary distractors. In Experiment 2A, participants performed a highly serial search through a group of similarly shaped moving letters. Performance was much slower when the target shared its color with a set of ignored static distractors. The exact same displays were used in Experiment 2B; however, participants now responded “present” for targets that shared the color of the static distractors. The same targets that had previously been difficult to find were now found efficiently. The results are interpreted in a flexible framework for attentional control. Targets that are linked with irrelevant distractors by color tend to be ignored. However, this cost can be overridden by top-down control settings.     

Strength cues and blocking at test promote reliable within-list criterion shifts in recognition memory

In seven experiments, we explored the potential for strength-based, within-list criterion shifts in recognition memory. People studied a mix of target words, some presented four times (strong) and others studied once (weak). In Experiments 1, 2, 4A, and 4B, the test was organized into alternating blocks of 10, 20, or 40 trials. Each block contained lures intermixed with strong targets only or weak targets only. In strength-cued conditions, test probes appeared in a unique font color for strong and weak blocks. In the uncued conditions of Experiments 1 and 2, similar strength blocks were tested, but strength was not cued with font color. False alarms to lures were lower in blocks containing strong target words, as compared with lures in blocks containing weak targets, but only when strength was cued with font color. Providing test feedback in Experiment 2 did not alter these results. In Experiments 3A–3C, test items were presented in a random order (i.e., not blocked by strength). Of these three experiments, only one demonstrated a significant shift even though strength cues were provided. Overall, the criterion shift was larger and more reliable as block size increased, and the shift occurred only when strength was cued with font color. These results clarify the factors that affect participants’ willingness to change their response criterion within a test list.     

Searching the same display twice: Properties of short-term memory in repeated search

Consecutive search for different targets in the same display is supported by a short-term memory mechanism: Distractors that have recently been inspected in the first search are found more quickly in the second search when they become the target (Exp. 1). Here, we investigated the properties of this memory process. We found that this recency advantage is robust to a delay between the two searches (Exp. 2) and that it is only slightly disrupted by an interference task between the two searches (Exp. 3). Introducing a concurrent secondary task (Exp. 4) showed that the memory representations formed in the first search are based on identity as well as location information. Together, these findings show that the short-term memory that supports repeated visual search stores a complex combination of item identity and location that is robust to disruption by either time or interference.     

The production effect in paired-associate learning: Benefits for item and associative information

In five experiments, we extended the production effect—better memory for items said aloud than for items read silently—to paired-associate learning, the goal being to explore whether production enhances associative information in addition to enhancing item information. In Experiments 1 and 2, we used a semantic-relatedness task in addition to the production manipulation and found no evidence of a production effect, whether the measure was cued recall or item recognition. Experiment 3 showed that the semantic-relatedness task had overshadowed the production effect; the effect was present when the semantic-relatedness task was removed, again whether cued recall or item recognition was the measure. Experiments 4 and 5 provided further evidence that production can enhance recall for word pairs and, using an associate recognition test with intact versus rearranged pairs, indicated that production may also enhance associative information. That production boosts memory for both types of information is considered in terms of distinctive encoding.     

Focused attention improves working memory: implications for flexible-resource and discrete-capacity models

Performance in working memory (WM) tasks depends on the capacity for storing objects and on the allocation of attention to these objects. Here, we explored how capacity models need to be augmented to account for the benefit of focusing attention on the target of recall. Participants encoded six colored disks (Experiment 1) or a set of one to eight colored disks (Experiment 2) and were cued to recall the color of a target on a color wheel. In the no-delay condition, the recall-cue was presented after a 1,000-ms retention interval, and participants could report the retrieved color immediately. In the delay condition, the recall-cue was presented at the same time as in the no-delay condition, but the opportunity to report the color was delayed. During this delay, participants could focus attention exclusively on the target. Responses deviated less from the target’s color in the delay than in the no-delay condition. Mixture modeling assigned this benefit to a reduction in guessing (Experiments 1 and 2) and transposition errors (Experiment 2). We tested several computational models implementing flexible or discrete capacity allocation, aiming to explain both the effect of set size, reflecting the limited capacity of WM, and the effect of delay, reflecting the role of attention to WM representations. Both models fit the data better when a spatially graded source of transposition error is added to its assumptions. The benefits of focusing attention could be explained by allocating to this object a higher proportion of the capacity to represent color.     

Breaking through the attentional window: Capture by abrupt onsets versus color singletons

Theeuwes (Psychonomic Bulletin & Review 11:65?C70, 2004) proposed that stimulus-driven capture occurs primarily for salient stimuli that fall within the observer??s attentional window, such as when performing a parallel search. This proposal, which is supported by some studies, can explain many seemingly discrepant results in the literature. The present study tested this proposal using a modified precuing paradigm. Search mode was manipulated via target?Cdistractor similarity in color space. In the parallel search condition, the orange target ??popped out?? from a set of distantly colored distractors (blue and green). In the serial search condition, the orange target was more difficult to find amongst a set of similarly colored distractors (yellow and red). In Experiments 1 and 2, cue validity effects for irrelevant-color singleton cues were greater under parallel than under serial search, at least partially replicating previous studies favoring the attentional-window account (e.g., Belopolsky, Zwaan, Theeuwes, & Kramer, Psychonomic Bulletin & Review 14:934?C938, 2007). We found the opposite pattern, however, for capture by abrupt onsets (Experiments 3 and 4), in which case capture effects were actually greater under serial search. In sum, parallel search appears to facilitate capture by color singletons, yet to inhibit capture by abrupt onsets.     

Animates are better remembered than inanimates: further evidence from word and picture stimuli

In three experiments, we showed that animate entities are remembered better than inanimate entities. Experiment 1 revealed better recall for words denoting animate than inanimate items. Experiment 2 replicated this finding with the use of pictures. In Experiment 3, we found better recognition for animate than for inanimate words. Importantly, we also found a higher recall rate of “remember” than of “know” responses for animates, whereas the recall rates were similar for the two types of responses for inanimate items. This finding suggests that animacy enhances not only the quantity but also the quality of memory traces, through the recall of contextual details of previous experiences (i.e., episodic memory). Finally, in Experiment 4, we tested whether the animacy effect was due to animate items being richer in terms of sensory features than inanimate items. The findings provide further evidence for the functionalist view of memory championed by Nairne and coworkers (Nairne, 2010; Nairne & Pandeirada, Cognitive Psychology, 61:1–22, 2010a, 2010b).     

Numerical distance effects in visual search

We present three experiments in which observers searched for a target digit among distractor digits in displays in which the mean numerical target?Cdistractor distance was varied. Search speed and accuracy increased with numerical distance in both target-present and target-absent trials (Exp. 1A). In Experiment 1B, the target 5 was replaced with the letter S. The results suggest that the findings of Experiment 1A do not simply reflect the fact that digits that were numerically closer to the target coincidentally also shared more physical features with it. In Experiment 2, the numerical distance effect increased with set size in both target-present and target-absent trials. These findings are consistent with the view that increasing numerical target?Cdistractor distance affords faster nontarget rejection and target identification times. Recent neurobiological findings (e.g., Nieder, 2011) on the neuronal coding of numerosity have reported a width of tuning curves of numerosity-selective neurons that suggests graded, distance-dependent coactivation of the representations of adjacent numbers, which in visual search would make it harder to reject numerically closer distractors as nontargets.     

The importance of context information for the spatial specificity of gaze cueing

In three experiments, we investigated the spatial allocation of attention in response to central gaze cues. In particular, we examined whether the allocation of attentional resources is influenced by context information—that is, the presence or absence of reference objects (i.e., placeholders) in the periphery. On each trial, gaze cues were followed by a target stimulus to which participants had to respond by keypress or by performing a target-directed saccade. Targets were presented either in an empty visual field (Exps. 1 and 2) or in previewed location placeholders (Exp. 3) and appeared at one of either 18 (Exp. 1) or six (Exps. 2 and 3) possible positions. The spatial distribution of attention was determined by comparing response times as a function of the distance between the cued and target positions. Gaze cueing was not specific to the exact cued position, but instead generalized equally to all positions in the cued hemifield, when no context information was provided. However, gaze direction induced a facilitation effect specific to the exact gazed-at position when reference objects were presented. We concluded that the presence of possible objects in the periphery to which gaze cues could refer is a prerequisite for attention shifts being specific to the gazed-at position.     

The mental wormhole: Internal attention shifts without regard for distance

Attention operates perceptually on items in the environment, and internally on objects in visuospatial working memory. In the present study, we investigated whether spatial and temporal constraints affecting endogenous perceptual attention extend to internal attention. A retro-cue paradigm in which a cue is presented beyond the range of iconic memory and after stimulus encoding was used to manipulate shifts of internal attention. Participants?? memories were tested for colored circles (Experiments 1, 2, 3a, 4) or for novel shapes (Experiment 3b) and their locations within an array. In these experiments, the time to shift internal attention (Experiments 1 and 3) and the eccentricity of encoded objects (Experiments 2?C4) were manipulated. Our data showed that, unlike endogenous perceptual attention, internal shifts of attention are not modulated by stimulus eccentricity. Across several timing parameters and stimuli, we found that shifts of internal attention require a minimum quantal amount of time regardless of the object eccentricity at encoding. Our findings are consistent with the view that internal attention operates on objects whose spatial information is represented in relative terms. Although endogenous perceptual attention abides by the laws of space and time, internal attention can shift across spatial representations without regard for physical distance.     

The effects of interleaving versus blocking on foreign language pronunciation learning

Many studies have shown that students learn better when they are given repeated exposures to different concepts in a way that is shuffled or interleaved, rather than blocked (e.g., Rohrer Educational Psychology Review, 24, 355–367, 2012). The present study explored the effects of interleaving versus blocking on learning French pronunciations. Native English speakers learned several French words that conformed to specific pronunciation rules (e.g., the long “o” sound formed by the letter combination “eau,” as in bateau), and these rules were presented either in blocked fashion (bateau, carreau, fardeau . . . mouton, genou, verrou . . . tandis, verglas, admis) or in interleaved fashion (bateau, mouton, tandis, carreau, genou, verglas . . .). Blocking versus interleaving was manipulated within subjects (Experiments 1–3) or between subjects (Experiment 4), and participants’ pronunciation proficiency was later tested through multiple-choice tests (Experiments 1, 2, and 4) or a recall test (Experiment 3). In all experiments, blocking benefited the learning of pronunciations more than did interleaving, and this was true whether participants learned only 4 words per rule (Experiments 1–3) or 15 words per rule (Experiment 4). Theoretical implications of these findings are discussed.     

Estimating working memory capacity for lists of nonverbal sounds

Working memory (WM) capacity limit has been extensively studied in the domains of visual and verbal stimuli. Previous studies have suggested a fixed WM capacity of typically about three or four items, on the basis of the number of items in working memory reaching a plateau after several items as the set size increases. However, the fixed WM capacity estimate appears to rely on categorical information in the stimulus set (Olsson & Poom Proceedings of the National Academy of Sciences 102:8776-8780, 2005). We designed a series of experiments to investigate nonverbal auditory WM capacity and its dependence on categorical information. Experiments 1 and 2 used simple tones and revealed capacity limit of up to two tones following a 6-s retention interval. Importantly, performance was significantly higher at set sizes 2, 3, and 4 when the frequency difference between target and test tones was relatively large. In Experiment 3, we added categorical information to the simple tones, and the effect of tone change magnitude decreased. Maximal capacity for each individual was just over three sounds, in the range of typical visual procedures. We propose that two types of information, categorical and detailed acoustic information, are kept in WM and that categorical information is critical for high WM performance.     

Dissociable yet tied inhibitory processes: The structure of inhibitory control

Cognitive and neural models have proposed the existence of a single inhibitory process that regulates behavior and depends on the right frontal operculum (rFO). The aim of this study was to make a contribution to the ongoing debate as to whether inhibition is a single process or is composed of multiple, independent processes. Here, within a single paradigm, we assessed the links between two inhibitory phenomena—namely, resistance to involuntary visual capture by abrupt onsets and resolving of spatial stimulus–response conflict. We did so by conducting three experiments, two involving healthy volunteers (Exps. 1 and 3), and one with the help of a well-documented patient, R.J., with selectively weakened inhibition following a lesion of the rFO. The results suggest that resistance to capture and stimulus–response conflict are independent, because (a) additive effects were found (Exps. 1 and 3), (b) capture did not correlate with compatibility effects (Exp. 1), (c) dual tasking affected the two phenomena differently (Exp. 3), and (d) a dissociation was found between the two in patient R.J. (Exp. 2). However, the results also show that these two phenomena may share some processing components, given that (a) both were affected in patient R.J., but to different degrees (Exp. 2), and (b) increasing the difficulty of dual tasking produced an increasingly negative correlation between capture and compatibility (Exp. 3), which suggests that when resources are withdrawn from the control of the former, they are used to control the latter.