The associated non-targets effect: evidence of nontarget processing at and beyond the level of letter recognition

In four visual search tasks participants were asked to make a target response if either of two targets was present and to make a nontarget response if neither target was present. Some target-absent displays included only nontarget stimuli or features that never occurred in the same displays as targets, whereas other target-absent displays included nontarget stimuli or features that did sometimes occur with targets. Nontarget responses were reliably faster in the former case than in the latter. This “associated nontargets effect” indicates that nontargets are not simply classified as nontargets but in addition are discriminated from one another. Current visual search models may underestimate the degree to which nontargets are processed during search.     

The associated nontargets effect: Evidence of nontarget processing at and beyond the level of letter recognition

In four visual search tasks participants were asked to make a target response if either of two targets was present and to make a nontarget response if neither target was present. Some target-absent displays included only nontarget stimuli or features that never occurred in the same displays as targets, whereas other target-absent displays included nontarget stimuli or features that did sometimes occur with targets. Nontarget responses were reliably faster in the former case than in the latter. This “associated nontargets effect” indicates that nontargets are not simply classified as nontargets but in addition are discriminated from one another. Current visual search models may underestimate the degree to which nontargets are processed during search.     

Nontarget detectability and interference with parafoveal target identification

A target and a flanking nontarget which shared no primary feature were exposed simultaneously in the parafoveal region of the left or right visual field. The presentation terminated with one of two metacontrast masks, one of which masked the nontarget significantly better than the other. One group of 8 subjects received nontargets which were detected better with one of the metacontrast masks, while another group of 8 subjects received nontargets which were detected better with the other mask. Target identification was significantly better when the nontarget appeared on its foveal side rather than on its peripheral side, and this superiority was independent of accuracy in detecting the nontarget. The lack of consistency of this result with models explaining the parafoveal identification asymmetry in terms of feature perturbations is emphasized. Asymmetric lateral inhibition is suggested as an explanation.     

Depth of nontarget processing in an attention task

Two studies examined the effect of the sensory discriminability of targets from nontargets on depth of nontarget processing. Subjects shadowed target words that were binaurally presented with coincident nontarget words. Targets and nontargets were spoken in the same male voice under low sensory discriminability and in male and female voices, respectively under high sensory discriminability. Across the two studies, depth of nontarget processing was assessed in three ways: extent to which shadowing accuracy was disrupted by a semantic overlap between targets and nontargets, expenditure of capacity (reaction time to subsidiary light signals), and nontarget recall. All three possible measures of depth of nontarget processing decreased as sensory discriminability increased. The data support the assumption of multiple-loci theories of attention that nontargets can be perceptually inhibited; they contraindicate the assumption of late-selection theories that perceptual processing is automatic and irrepressible.     

多目标追踪任务中不同运动方式非目标的抑制机制

采用多目标追踪范式结合点探测技术的方法, 考察视觉系统对不同运动方式(静止和规则运动)非目标的抑制机制。实验一将部分非目标设置为静止, 考察静止非目标的抑制机制; 实验二将部分非目标设置为规则运动, 以提高任务难度, 考察规则运动非目标的抑制机制。结果发现: (1) 实验一中静止非目标受到抑制, 抑制量与运动非目标没有差异; (2) 实验二中规则运动非目标受到抑制, 抑制量显著小于随机运动非目标; (3)综合两实验发现, 随着任务难度的提高, 只有随机运动非目标的抑制量显著增加, 而静止非目标与规则运动非目标的抑制量差异不显著。最后, 就视觉系统对不同运动方式非目标的抑制机制进行了讨论。     

Mechanisms of the associated nontargets effect: processes influenced by statistical learning in a simple visual environment

In three visual search experiments participants were asked to make a target response if either of two targets was present and to make a nontarget response if neither target was present. Some target-absent displays included only nontarget features that never occurred in the same displays as target features, whereas other target-absent displays included nontarget features that did sometimes occur with target features. Nontarget responses were reliably faster in the former case than in the latter. This “associated nontargets effect” appears to arise from participants' ability to learn and to use contingencies between the presence of certain nontargets and the absence of any target.     

Mechanisms of the associated nontargets effect: Processes influenced by statistical learning in a simple visual environment

In three visual search experiments participants were asked to make a target response if either of two targets was present and to make a nontarget response if neither target was present. Some target-absent displays included only nontarget features that never occurred in the same displays as target features, whereas other target-absent displays included nontarget features that did sometimes occur with target features. Nontarget responses were reliably faster in the former case than in the latter. This “associated nontargets effect” appears to arise from participants' ability to learn and to use contingencies between the presence of certain nontargets and the absence of any target.     

Nontarget columns and parafoveal target identification: Some limits on previously observed effects

Summary Three experiments were conducted to determine limits to the phenomenon in which a column of nontargets to the foveal side of a parafoveally presented target is more detrimental to identification than a column to the target's peripheral side, while a single nontarget to the peripheral side is more disruptive. Experiments 1 and 2 showed that proximity of nontarget characters in a column is not sufficent to produce the difference in the effect of the position of nontarget columns and single nontargets. Physical features of characters in the column allowing closure emerged as important to the effect of its position on target identification. Experiment 3 confirmed the findings of the first two experiments and showed, in addition, that performance is better with nontarget columns than with single nontargets because characters in the columns exert lateral interference on one another and thereby release such interference on the target.     

The costs of target prioritization and the external requirements for using a recall-to-reject strategy in memory exclusion tasks: a meta-analysis

In event-related potential (ERP) studies, the left-parietal old/new effect is commonly considered as a neural correlate of recollection. In memory exclusion tasks, the effect is usually observed when the targeted information is identified, but it is not necessarily present when studied items are rejected as nontargets. Interestingly, both the presence and the absence of such old/new effects to nontargets have been regarded as indicator for strategic retrieval. We reviewed previous ERP studies using memory exclusion tasks to analyze the reaction time (RT) pattern in such studies, as well as the influence of task difficulty on the occurrence of nontarget retrieval. We identified 44 test conditions, reported in 24 studies, and subjected the behavioral data to a meta-analysis. The RTs to correctly rejected new items were shorter than the RTs to hits, in particular in studies that required differentiating conceptual or perceptual information at test. When the retrieval of target information was prioritized, RTs to nontargets were delayed relative to targets. Without such prioritization, no such RT differences were observed. For test conditions with nontarget retrieval, the retrieval accuracy was poorer compared with test conditions without such retrieval. The findings support previous studies that claimed that nontarget retrieval becomes more likely when target retrieval is difficult, but the strong overlap in task difficulty between conditions with and without nontarget retrieval indicates that other, partly yet to-be-identified factors contribute to the occurrence of nontarget retrieval as well.     

Accuracy of target detection in new-object and old-object displays

In 4 experiments, the authors investigated accuracy of detecting a target among nontargets. In some experiments, the target was a second-order square of stationary lines on a background of downward-moving lines, and nontargets were second-order squares of upward-moving lines. In other experiments, target and nontarget squares and background were shades of gray. The principal comparison was between "new" and "old" object displays. In new-object displays, search items appeared abruptly and one might be a target. In old-object displays, search items appeared abruptly, and after a delay one might become a target. Search displays in both conditions terminated shortly after target onset. Except when target onset was associated with the sole luminance change in a display, targets were much better detected in new- than in old-object displays. It is suggested that object onsets elicit a brief stimulus-driven enhancement of attention to the new objects.     

多目标追踪的任务难度对不同类型非目标选择性抑制的影响

采用多目标追踪（MOT）与点探测刺激觉察任务相结合的实验范式,分别通过改变运动与静止非目标数量,考察追踪难度变化对不同类型非目标选择性抑制的影响。实验一通过改变运动非目标数量为4、5、6,发现当运动非目标数量为6时,追踪难度显著增加,静止非目标上的抑制量也显著增加,而运动非目标上的抑制量则不随追踪难度的变化而变化;实验二改变静止非目标数量为4、5、6,同样发现当静止非目标数量为6时,追踪难度显著增加,静止非目标上的抑制量也显著增加,而运动非目标上的抑制量仍不随追踪难度的变化而变化,且当静止非目标数量为6时,静止非目标上的抑制量显著大于运动非目标,出现了反转现象,其原因可能是视野范围内总的对象数量超出了视觉索引容量,被试改变了对静止与运动非目标的抑制策略。综合实验结果表明,静止非目标上的抑制程度随追踪难度的提高而增加;而运动非目标上的抑制程度对追踪难度的变化不敏感,在不同难度水平上保持相对稳定。     

Methylphenidate speeds evaluation processes of Attention Deficit Disorder adolescents during a continuous performance test

Fortysix Attention Deficit Disorder (ADD) adolescents took a Continuous Performance Test (CPT) under placebo and methylphenidate (35.33 mg/day). The task required pressing one button for targets (p=133),and another button for nontargets. Subjects displayed a strong bias to make the more frequent negative response before completely evaluating stimuli. Consistent with this assumption, subjects responded faster (by an average of 87 ms) to nontargets than to targets. Methylphenidate increased accuracy and speeded reaction times (RTs) to targets. The drug also increased the amplitude of the P3b component of the eventrelated potential for nontargets and shortened the latency of P3b for both targets and nontargets. These results suggest increased capacity allocation to and faster evaluation of task stimuli. Finally, the stimulant lengthened relative motor processing time (RT-P3b latency) for nontargets, a finding implying that response processing was accomplished with the benefit of earlier completion of evaluation processes for these stimuli.Portions of these findings were reported at the meeting of the Society for Research in Child and Adolescent Psychopathology, Costa Mesa, California, January 24–26, 1990. This research was supported by NIMH grant MH38118 to the first author. We thank the late Helen Pollock and the University of Rochester's Strong Memorial Hospital Pharmacy Manufacturing Department for their help.     

Target localization after saccades and at fixation: Nontargets both facilitate and bias responses

ABSTRACT

The image on our retina changes every time we make an eye movement. To maintain visual stability after saccades, specifically to locate visual targets, we may use nontarget objects as “landmarks”. In the current study, we compared how the presence of nontargets affects target localization after saccades and during sustained fixation. Participants fixated a target object, which either maintained its location on the screen (sustained-fixation trials), or displaced to trigger a saccade (saccade trials). After the target disappeared, participants reported the most recent target location with a mouse click. We found that the presence of nontargets decreased response error magnitude and variability. However, this nontarget facilitation effect was not larger for saccade trials than sustained-fixation trials, indicating that nontarget facilitation might be a general effect for target localization, rather than of particular importance to post-saccadic stability. Additionally, participants’ responses were biased towards the nontarget locations, particularly when the nontarget-target relationships were preserved in relative coordinates across the saccade. This nontarget bias interacted with biases from other spatial references, e.g., eye movement paths, possibly in a way that emphasized non-redundant information. In summary, the presence of nontargets is one of several sources of reference that combine to influence (both facilitate and bias) target localization.     

Categorization and identification of simultaneous targets.

Early and late selection theories of visual attention disagree about whether identification occurs before or after selection. Studies showing the category effect, i.e., the time to detect a letter is hardly affected by the number of digits present in the display, are taken as evidence for late selection theories since these studies suggest parallel identification of all items in the display. As an extension of previous studies, in the present study two categorically different targets were presented simultaneously among a variable number of nontargets. Subjects were shown brief displays of two target letters among either 2, 4 or 6 nontarget digits. Subjects responded 'same' when the two letters were identical and 'different' otherwise. Since the 'same-different' response reflects the combined outcome of the simultaneous targets, late-selection theory predicts that the time to match the target letters is independent of the number of nontarget digits. Alternatively, early-selection theory predicts a linear increase of reaction time with display size since the presence of more than one target disrupts parallel preattentive processing, leading to a serial search through all items in the display. The results provide evidence for the early-selection view since reaction time increased linearly with the number of categorically different nontargets. A control experiment revealed that none of the alternative explanations could account for the display size effect.     

Boundary conditions on parallel processing in human vision

A new theory of visual search is tested experimentally with simple colour patches. The essential element of this new theory is that, whatever the search materials, efficiency increases continuously with (i) decreasing similarity between targets and nontargets, and (ii) increasing similarity between one nontarget and another. Control of 'attention' (access to visual short-term memory) is seen as a competitive interaction between display elements, and the theory shows how stimulus similarities influence the outcome of this competition. One alternative view is that parallel visual processes are limited to local mismatch detection. Search is parallel if the target forms a break in an otherwise homogeneous field, but is serial when absolute stimulus identification is required. It is shown, however, that even colour identification can be parallel, providing targets and nontargets are sufficiently dissimilar. A second alternative view is that search for simple features is parallel whereas search for conjunctions is serial. Conjunction search, however, has a characteristic similarity structure: different kinds of nontarget each share one relevant attribute with the target, but none with one another. When this structure is mimicked in search for colour patches, correspondingly poor performance is obtained.     

ERP evidence for the control of emotional memories during strategic retrieval

Neural evidence for the strategic retrieval of task-relevant ‘target’ memories at the expense of less relevant ‘nontarget’ memories has been demonstrated across a wide variety of studies. In ERP studies, this evidence consists of the ERP correlate of recollection (i.e. the ‘left parietal old/new effect’) being evident for targets and attenuated for nontargets. It is not yet known, however, whether this degree of strategic control can be extended to emotionally valenced words, or whether these items instead reactivate associated memories. The present study used a paradigm previously employed to demonstrate the strategic retrieval of neutral words (Herron & Rugg, Psychonomic Bulletin and & Review, 10(3), 703-–710, 2003b) to assess the effects of stimulus valence on behavioural and event-related potential (ERP) measures of strategic retrieval. While response accuracy and reaction times associated with targets were unaffected by valence, negative nontargets and new items were both associated with an elevated false alarm rate and longer RTs than their neutral equivalents. Both neutral and negative targets and nontargets elicited early old/new effects between 300 and 500 ms. Critically, whereas neutral and negative targets elicited robust and statistically equivalent left parietal old/new effects between 500 and 800 ms, these were absent for neutral and negative nontargets. A right frontal positivity associated with postretrieval monitoring was evident for neutral targets versus nontargets, for negative versus neutral nontargets, and for targets versus new items. It can therefore be concluded that the recollection of negatively valenced words is subject to strategic control during retrieval, and that postretrieval monitoring processes are influenced by emotional valence.     

Preferential processing of target features in texture segmentation

In five experiments, observers were required to detect a texture target and/or identify the orientation of elements composing target and nontarget regions. They were significantly worse at discerning the orientation of nontarget regions than at detecting target presence (Experiment 1). On the other hand, accuracy of identifying target orientation was found to be near 100% (Experiment 2). When observers were required only to identify surround orientation (Experiment 3), accuracy was diminished on target-present trials relative to that on target-absent trials. The superiority of target processing and the interference produced by target presence on surround processing were demonstrated in unpracticed observers (Experiment 4). In Experiment 5, it was found that information regarding target presence is available before information regarding feature values of the target. These findings are consistent with a model of visual attention and search that incorporates a fast generalized difference operator and a slower feature comparison process.     

Perceptual processing of nontargets in an attention task

The capability of nontargets to qualitatively influence the semantic processing of coincident targets was investigated in three experiments. Subjects were aurally presented a series of word pairs and attempted to detect homonymic instances of a predesignated category (e.g., animals). The nontarget with which a target (e.g., ANT) was paired was appropriate (e.g., CRAWLING), inappropriate (e.g., UNCLE), or neutral (e.g., STRAW). Experiments 1 and 2 established that detection of targets can be facilitated by appropriate nontargets and inhibited by inappropriate ones. Thus, nontargets can influence the way in which targets are semantically represented. Experiment 3 showed that this effect is eliminated when subjects are precued as to the ear of entry of targets. Thus, precuing appears to curtail the perceptual processing of nontargets. The data run counter to theories that claim that focused attention does not entail the perceptual suppression of nontargets.     

Electrophysiological correlates of high-level perception during spatial navigation

We studied the electrophysiological basis of object recognition by recording scalp electroencephalograms while participants played a virtual-reality taxi driver game. Participants searched for passengers and stores during virtual navigation in simulated towns. We compared oscillatory brain activity in response to store views that were targets or nontargets (during store search) or neutral (during passenger search). Even though store category was solely defined by task context (rather than by sensory cues), frontal electrophysiological activity in the low frequency bands (primarily in the θ [4–8 Hz] band) reliably distinguished between the target, nontarget, and neutral store views. These results implicate low-frequency oscillatory brain activity in frontal regions as an important variable in the study of the cognitive processes involved in object recognition, categorization, and other forms of high-level perception.     

Individual differences in prejudice and associative versus rule‐based forms of transitive reasoning

Two experiments examined whether individual differences in prejudice are associated with different reasoning styles when targets and nontargets of prejudice are processed in the same context. High‐prejudice and low‐prejudice participants studied pairwise relations between four persons (one a prejudice target, three nontargets). Stereotypes were made salient by using specific ethnic names and stereotypic traits to define relations between the targets. Relations between the persons were always stereotype congruent in Experiment 1, whereas they were sometimes stereotype incongruent in Experiment 2. We examined study time, relational memory, and transitive reasoning in both experiments. The results of both experiments indicated that the high‐prejudice participants studied sets of relations presented to them faster than did the low‐prejudice participants. The high‐prejudice participants were also more likely to show impaired relational memory and reasoning about nontarget persons but no such limitations with respect to target persons. This novel evidence that prejudice might substantially impair memory and transitive reasoning processes about nontarget persons is discussed in the light of alternative theoretical frameworks in the social cognition and emotion domains. Copyright © 2011 John Wiley & Sons, Ltd.