Visual search asymmetry: The influence of stimulus familiarity and low-level features

Wang, Cavanagh, and Green (1994) demonstrated a pop-out effect in searching for an unfamiliar target among familiar distractors (U—F search) and argued for the importance of a familiarity difference between the target and the distractors in determining search efficiency. In four experiments, we explored the generality of that finding. Experiment 1 compared search efficiency across a variety of target-distractor pairs. In Experiments 2, 3, and 4, we used Chinese characters and their transforms as targets and distractors and compared search performance between Chinese and non-Chinese participants. We demonstrated that search asymmetry and search efficiency in the U—F condition are influenced by the presence of low-level feature differences between the familiar and the unfamiliar stimuli. Our findings suggest that the familiarity of the distractors, rather than the familiarity difference between the target and the distractors, determines search efficiency. We also documented a counterintuitive familiarity-inferiority effect, suggesting that knowledge of search stimuli may, sometimes, be detrimental to search performance.     

Distractor familiarity leads to more efficient visual search for complex stimuli

Previous reports suggest that distractor familiarity plays an important role in determining visual search efficiency. However, the specific tasks used in those studies limit the extension of their findings to real-world situations and everyday images. In the present study, subjects engaged in a prolonged period of search experience as a control of their level of familiarity with a large set of target and distractor images. Reaction times and search slopes decreased dramatically over this period, especially for trials with a large target eccentricity and many distractors. Following extended practice, search among familiar distractors was more efficient than search among unfamiliar distractors. Furthermore, we found that familiar targets were located more efficiently than unfamiliar targets and that subjects were faster at locating targets that they had experienced in the majority of the search trials. These results show that prolonged visual experience facilitates processing of both target and distractor items during search.     

Local and global factors of similarity in visual search

Effects of the similarity between target and distractors in a visual search task were investigated in several experiments. Both familiar (numerals and letters) and unfamiliar (connected figures in a 5 × 5 matrix) stimuli were used. The observer had to report on the presence or absence of a target among a variable number of homogeneous distractors as fast and as accurately as possible. It was found that physical difference had the same clear effect on processing time far familiar and for unfamiliar stimuli: processing time decreased monotonically with increasing physical difference. Distractors unrelated to the target and those related to the target by a simple transformation (180° rotation, horizontal or vertical reflection) were also compared, while the physical difference was kept constant. For familiar stimuli, transformational relatedness increased processing time in comparison with that fort unrelated stimulus pairs. It was further shown in a scaling experiment that this effect could be accounted for by the amount of perceived similarity of the target-distractor pairs. For unfamiliar stimuli, transformational relatedness did have a smaller and less pronounced effect. Various comparable unrelated distractors resulted in a full range of processing times. Results from a similarity scaling experiment correlated well with the outcome of the experiments with unfamiliar stimuli. These results are interpreted in terms of an underlying continuum of perceived similarity as the basis of the speed of visual search, rather than a dichotomy of parallel versus serial processing.     

Interference from familiar natural distractors is not eliminated by high perceptual load

A crucial prediction of perceptual load theory is that high perceptual load can eliminate interference from distractors. However, Lavie et al. (Psychol Sci 14:510–515, 2003) found that high perceptual load did not eliminate interference when the distractor was a face. The current experiments examined the interaction between familiarity and perceptual load in modulating interference in a name search task. The data reveal that high perceptual load eliminated the interference effect for unfamiliar distractors that were faces or objects, but did not eliminate the interference for familiar distractors that were faces or objects. Based on these results, we proposed that the processing of familiar and natural stimuli may be immune to the effect of perceptual load.     

The hard-won benefits of familiarity in visual search: naturally familiar brand logos are found faster

Familiar items are found faster than unfamiliar ones in visual search tasks. This effect has important implications for cognitive theory, because it may reveal how mental representations of commonly encountered items are changed by experience to optimize performance. It remains unknown, however, whether everyday items with moderate levels of exposure would show benefits in visual search, and if so, what kind of experience would be required to produce them. Here, we tested whether familiar product logos were searched for faster than unfamiliar ones, and also familiarized subjects with previously unfamiliar logos. Subjects searched for preexperimentally familiar and unfamiliar logos, half of which were familiarized in the laboratory, amongst other, unfamiliar distractor logos. In three experiments, we used an N-back-like familiarization task, and in four others we used a task that asked detailed questions about the perceptual aspects of the logos. The number of familiarization exposures ranged from 30 to 84 per logo across experiments, with two experiments involving across-day familiarization. Preexperimentally familiar target logos were searched for faster than were unfamiliar, nonfamiliarized logos, by 8 % on average. This difference was reliable in all seven experiments. However, familiarization had little or no effect on search speeds; its average effect was to improve search times by 0.7 %, and its effect was significant in only one of the seven experiments. If priming, mere exposure, episodic memory, or relatively modest familiarity were responsible for familiarity’s effects on search, then performance should have improved following familiarization. Our results suggest that the search-related advantage of familiar logos does not develop easily or rapidly.     

The effect of background familiarity in visual search: An analysis of underlying factors

The speed and accuracy of visual target search are strongly dependent on the familiarity of the background through which the search proceeds. Search through unfamiliar elements is much more difficult than search through familiar ones. This effect of background familiarity is examined in a series of three experiments. Experiment 1 suggests that the effect is not attributable to an inherently slow classification of individually unfamiliar nontargets. Experiments 2 and 3 investigate three aspects of multicharacter processing potentially sensitive to background familiarity. The results suggest that the background familiarity effect is most parsimoniously viewed as the result of slow or inaccurate segmentation of features extracted from adjacent characters. Mechanisms linking the familiarity of the background with the efficiency of character segregation are discussed in closing.     

You do not find your own face faster; you just look at it longer

Previous studies investigating the ability of high priority stimuli to grab attention reached contradictory outcomes. The present study used eye tracking to examine the effect of the presence of the self-face among other faces in a visual search task in which the face identity was task-irrelevant. We assessed whether the self-face (1) received prioritized selection (2) caused a difficulty to disengage attention, and (3) whether its status as target or distractor had a differential effect. We included another highly familiar face to control whether possible effects were self-face specific or could be explained by high familiarity. We found that the self-face interfered with the search task. This was not due to a prioritized processing but rather to a difficulty to disengage attention. Crucially, this effect seemed due to the self-face’s familiarity, as similar results were obtained with the other familiar face, and was modulated by the status of the face since it was stronger for targets than for distractors.     

The effect of familiarity on visual-search performance: evidence for learned basic features.

In this study, the effects of familiarity on visual search were investigated. To avoid any confounding between familiarity and visual-feature differences between item pairs, Ns and mirror-Ns were presented as target and as distractors to a group of German participants and to a group of Slavic participants. For the Germans only N was familiar, whereas for the Slavs both N and mirror-N were familiar. The results show that search was difficult only when the Germans had to find an N among mirror-Ns. In any other case, search was efficient. Therefore, our results demonstrate that, contrary to earlier suggestions, search for a familiar item among familiar distractors can be easy. This supports the hypothesis that familiarity improves distractor grouping. However, the data are also compatible with the idea that letters are standard or basic features, which implies that basic features can be learned.     

自我信息加工优势中的熟悉性问题

熟悉性对于自我信息加工优势的影响往往与自我相关性的作用交织在一起,从而使其成为该领域的一个研究重点和难点。文章分别介绍了自我参照效应、自我面孔和人名识别研究中对该问题进行考察的主要思路与发现。现有证据显示,熟悉性与自我特异性在自我信息的加工优势中是可分离的,从而表明自我信息所固有的高熟悉性可能并不是造成其具有加工优势的决定性因素。文章在展望部分将熟悉性进一步细分为材料的熟悉性与任务的熟悉性,并提出未来的研究应该特别注意考察任务熟悉性可能存在的影响作用。     

Effect of local fluency gradient of objects creates search asymmetry

Search asymmetry is a phenomenon in which search efficiency in a visual-search task differs for searching for an X target among Y distractors from search for a Y target among X distractors. Previous research shows that search asymmetry is mainly produced by a difference in the whole signal strength of items or a difference in item familiarity. This study reports that a difference in the local fluency within items also affects search efficiency and generates search asymmetry. Fluency is a value that correlates with the processing efficiency of an item. In particular, five experiments reveal that search efficiency for two part items depends on whether a fluent part is the top or bottom portion of a target (vs. distractor). We argue that this type of search asymmetry implicates the operation of an unknown mechanism that detects local fluency gradient in visual processing.     

The influence of incongruity and preexposure on the familiarity effect in visual selection of children

A consistent finding in the literature concerning visual selection is that Ss will spend more time viewing unfamiliar stimuli than stimuli with which they have been familiarized. In the present experiment, the relationship between the magnitude of this familiarity effect and the level of stimulus incongruity was examined and found to be monotonic and increasing. In addition, amount of stimulus preexposure had no significant effect on the magnitude of the familiarity effect. Furthermore, there was no overall difference in Ss' preference for familiar and unfamiliar stimuli. Results are interpreted as supporting a theory of visual selection based on information-conflict resolution.     

The effect of familiarity on visual-search performance: Evidence for learned basic features

In this study, the effects of familiarity on visual search were investigated. To avoid any confounding between familiarity and visual-feature differences between item pairs,Ns and mirror-Ns were presented as target and as distractors to a group of German participants and to a group of Slavic participants. For the Germans onlyN was familiar, whereas for the Slavs bothN and mirror-N were familiar. The results show that search was difficult only when the Germans had to find anN among mirror-Ns. In any other case, search was efficient. Therefore, our results demonstrate that, contrary to earlier suggestions, search for a familiar item among familiar distractors can be easy. This supports the hypothesis that familiarity improves distractor grouping. However, the data are also compatible with the idea that letters are standard or basic features, which implies that basic features can be learned.     

An attention account of neural priming

Repetition priming of familiar stimuli (e.g., objects) produces a decrease in visual cortical activity for repeated versus novel items, which has been attributed to more fluent processing for repeated items. By contrast, priming of unfamiliar stimuli (e.g., abstract shapes) produces an increase in visual cortical activity. The mechanism for priming-related increases in activity for repeated unfamiliar stimuli is unknown. We hypothesised that such increases in activity may reflect attentional allocation to these items. We tested this hypothesis using a priming-spatial attention paradigm. During Phase 1 of Experiment 1, participants viewed unfamiliar abstract shapes and familiar objects. During Phase 2, participants identified target letters (S or H). Each target letter was preceded by a non-informative shape or object cue that was repeated (from Phase 1) or novel in the same (valid) or opposite (invalid) hemifield. In Experiment 2, we manipulated shape familiarity by presenting shapes once or six times during Phase 1. For both experiments, at valid locations, target identification accuracy was higher following repeated versus novel unfamiliar item cues and lower following repeated versus novel familiar item cues. These findings support our hypothesis that priming-related increases in visual cortical activity for repeated unfamiliar items may, in part, reflect attentional allocation.     

Making heads turn: the effect of familiarity and stimulus rotation on a gender-classification task

Recent work has demonstrated that facial familiarity can moderate the influence of inversion when completing a configural processing task. Here, we examine whether familiarity interacts with intermediate angles of orientation in the same way that it interacts with inversion. Participants were asked to make a gender classification to familiar and unfamiliar faces shown at seven angles of orientation. Speed and accuracy of performance were assessed for stimuli presented (i) as whole faces and (ii) as internal features. When presented as whole faces, the task was easy, as revealed by ceiling levels of accuracy and no effect of familiarity or angle of rotation on response times. However, when stimuli were presented as internal features, an influence of facial familiarity was evident. Unfamiliar faces showed no increase in difficulty across angle of rotation, whereas familiar faces showed a marked increase in difficulty across angle, which was explained by significant linear and cubic trends in the data. Results were interpreted in terms of the benefit gained from a mental representation when face processing was impaired by stimulus rotation.     

Internal feature saliency as a marker of familiarity and configural processing

Two experiments that explore the internal feature advantage (IFA) in familiar face processing are reported. The IFA involves more efficient processing of internal features for familiar faces over unfamiliar ones. Experiment 1 examined the possibility of a configural basis for this effect through use of a matching task for familiar and unfamiliar faces presented both upright and upside-down. Results revealed the predicted IFA for familiar faces when stimuli were upright, but this was removed when stimuli were inverted. Experiment 2 examined the degree of training required before the IFA was demonstrated. Latency results revealed that whilst 90–180 s of exposure was sufficient to generate an IFA of intermediate magnitude, 180–270 s of exposure was required before the IFA was equivalent to that demonstrated for a familiar face. Taken together, these results offer three conclusions: First, the IFA is reaffirmed as an objective indicator of familiarity; second, the IFA is seen to rest on configural processing; and finally, the development of the IFA with familiarity indicates a development of configural processing with familiarity. As such, insight is gained as to the type of processing changes that occur as familiarity is gradually acquired.     

Repetition effects for words and nonwords as indexed by event-related fMRI: a preliminary study

We have previously shown differential effects of stimulus familiarity on the repetition-related responses in right fusiform cortex to both faces and symbols. Repetition of familiar stimuli produced a response decrease, whereas repetition of unfamiliar stimuli produced a response increase. In the present experiment, we used words and nonwords as the familiar and unfamiliar stimuli respectively. In this case, the only fusiform region showing the familiarity-by-repetition interaction was in anterior left fusiform. This left-lateralisation of the fusiform interaction is consistent with our hypothesis that these repetition-related effects occur in the same regions responsible for perceptual recognition of familiar stimuli.     

Influence of attentional focus on skilled motor performance: Performance decrement under unfamiliar focus conditions

Recent studies have demonstrated that the direction of attentional focus exerts a substantial influence on motor performance. We argue that in well-learned skills, this variable might be confounded with athletes’ familiarity with focus conditions. We studied the effect of familiarity and the direction of attentional focus on performance in two experiments using 2 (familiarity) × 2 (direction) within-subject designs. A significant main effect of familiarity—that is, better performance under familiar compared with unfamiliar focus conditions—confirmed the influence of familiarity on motor performance. Results are consistent with existing concepts, but lead to different consequences when applied to sport and exercise.     

Attention capture by contour onsets and offsets: No special role for onsets

In five experiments, we investigated the power of targets defined by the onset or offset of one of an object’s parts (contour onsets and offsets) either to guide or to capture visual attention. In Experiment 1, search for a single contour onset target was compared with search for a single contour offset target against a static background of distractors; no difference was found between the efficiency with which each could be detected. In Experiment 2, onsets and offsets were compared for automatic attention capture, when both occurred simultaneously. Unlike in previous studies, the effects of overall luminance change, new-object creation, and number of onset and offset items were controlled. It was found that contour onset and offset items captured attention equally well. However, display size effects on both target types were also apparent. Such effects may have been due to competition for selection between multiple onset and offset stimuli. In Experiments 3 and 4, single onset and offset stimuli were presented simultaneously and pitted directly against one another among a background of static distractors. In Experiment 3, we examined “guided search,” for a target that was formed either from an onset or from an offset among static items. In Experiment 4, the onsets and offsets were uncorrelated with the target location. Similar results occurred in both experiments: target onsets and offsets were detected more efficiently than static stimuli which needed serial search; there remained effects of display size on performance; but there was still no advantage for onsets. In Experiment 5, we examined automatic attention capture by single onset and offset stimuli presented individually among static distractors. Again, there was no advantage for onset over offset targets and a display size effect was also present. These results suggest that, both in isolation and in competition, onsets that do not form new objects neither guide nor gain automatic attention more efficiently than offsets. In addition, in contrast to previous studies in which onsets formed new objects, contour onsets and offsets did not reliably capture attention automatically.     

You sound familiar: carrion crows can differentiate between the calls of known and unknown heterospecifics

In group-living animals, it is adaptive to recognize conspecifics on the basis of familiarity or group membership as it allows association with preferred social partners and avoidance of competitors. However, animals do not only associate with conspecifics but also with heterospecifics, for example in mixed-species flocks. Consequently, between-species recognition, based either on familiarity or even individual recognition, is likely to be beneficial. The extent to which animals can distinguish between familiar and unfamiliar heterospecifics is currently unclear. In the present study, we investigated the ability of eight carrion crows to differentiate between the voices and calls of familiar and unfamiliar humans and jackdaws. The crows responded significantly more often to unfamiliar than familiar human playbacks and, conversely, responded more to familiar than unfamiliar jackdaw calls. Our results provide the first evidence that birds can discriminate between familiar and unfamiliar heterospecific individuals using auditory stimuli.     

Visual laterality in dolphins when looking at (un)familiar humans

Understanding the evolution of brain lateralisation including the origin of human visual laterality requires an understanding of brain lateralisation in related animal species. However, little is known about the visual laterality of marine mammals. To help correct this lack, we evaluated the influence of familiarity with a human on the visual response of five captive bottlenose dolphins. Dolphins gazed longer at unfamiliar than at familiar humans, revealing their capacity to discriminate between these two types of stimuli. Pooled data for responses to all test stimuli demonstrated a preferential use of left eye by all our five dolphin subjects. However, familiarity with particular humans did not influence preferential use of a given eye. Finally, we compared our results with those on other vertebrates.