Bozana Meinhardt-Injac

The time course of face matching by internal and external features: Effects of context and inversion.

Effects of context and inversion were studied in face matching tasks by measuring proportion correct as a function of exposure duration. Subjects were instructed to attend either internal features (task A) or external features (task B) and matched two consecutive face stimuli, which included either congruent, incongruent, or no facial context features. In congruent contexts matching performance rose fast and took very similar courses for both types of facial features. With no contexts internal and external features were found to be matched at an equal speed, while incongruent contexts seriously delayed matching performance for internal, but not for external features. Analysing the effects of context and inversion showed strong interactions with time scale and the features to be attended. At brief timings effects of inversion and context were strong for both feature types. At longer exposure durations there were pronounced effects of inversion and context for internal features while for external features inversion effects were absent and context effects at just moderate degrees. Moreover, deteriorating effects of incongruent contexts, which were strong at brief timings, were attenuated at longer exposure durations, while facilitative effects of congruent contexts resided at high levels. These findings indicate that global and holistic processing modes dominate the early epoch of the face specific visual response, but can be replaced by modes that allow observers to regulate contextual influences and to access facial features more focused when the first 200 ms have passed.

Holistic processing and reliance on global viewing strategies in older adults' face perception

There is increasing evidence that face recognition might be impaired in older adults, but it is unclear whether the impairment is truly perceptual, and face specific. In order to address this question we compared performance in same/different matching tasks with face and non-face objects (watches) among young (mean age 23.7) and older adults (mean age 70.4) using a context congruency paradigm (Meinhardt-Injac, Persike & Meinhardt, 2010, Meinhardt-Injac, Persike and Meinhardt, 2011a). Older adults were less accurate than young adults with both object classes, while face matching was notably impaired. Effects of context congruency and inversion, measured as the hallmarks of holistic processing, were equally strong in both age groups, and were found only for faces, but not for watches. The face specific decline in older adults revealed deficits in handling internal facial features, while young adults matched external and internal features equally well. Comparison with non-face stimuli showed that this decline was face specific, and did not concern processing of object features in general. Taken together, the results indicate no age-related decline in the capabilities to process faces holistically. Rather, strong holistic effects, combined with a loss of precision in handling internal features indicate that older adults rely on global viewing strategies for faces. At the same time, access to the exact properties of inner face details becomes restricted.

The context effect in face matching: Effects of feedback

Faces are perceived holistically, even when they are presented briefly (Hole, 1994; Richler, Mack, et al., 2009). Results obtained with a context congruency paradigm support dominance of holistic processing for brief timings, but indicate that larger viewing times enable observers to regulate contextual influences, and to use a feature selective focus (Meinhardt-Injac, Persike, & Meinhardt, 2010). Here we provide further evidence for this claim, and illuminate the role of feedback. With trial by trial feedback observers show poor performance in incongruent facial contexts at brief timings, but become quite effective in suppressing information that interferes with the correct judgements at larger viewing times. Without feedback they are still able to delimit the effects of conflicting contextual information, but are less effective. Adding further target features leads to moderate performance increase in incongruent contexts when there is no feedback, but to strong improvement when feedback is provided. These findings indicate that observers use opportunities of learning to replace holistic face perception by modes of active vision when sufficient temporal resources are available.

The context congruency effect is face specific

There is evidence that faces are processed by specialized and independent modules that treat them as global configurations, or wholes (Axelrod & Yovel, 2010; Kanwisher, McDermott, & Chun, 1997). The holistic nature of face perception has been demonstrated with several experimental paradigms designed to examine whether facial parts interact, or are accessed independently. A recently introduced paradigm (Meinhardt-Injac, Persike, & Meinhardt, 2010) measures the strength of contextual interaction among internal and external facial features in congruent and incongruent target/no-target relationships. For this paradigm it is shown that the context congruency effect is indeed face specific: A strong and asymmetric contextual interaction of the inner and the outer stimulus regions exists for faces, but is absent for watches, which represent a non-facial object class with a comparable inner/outer object structure.

The complete design in the composite face paradigm: role of response bias, target certainty, and feedback

Some years ago an improved design (the “complete design”) was proposed to assess the composite face effect in terms of a congruency effect, defined as the performance difference for congruent and incongruent target to no-target relationships (Cheung et al., 2008). In a recent paper Rossion (2013) questioned whether the congruency effect was a valid hallmark of perceptual integration, because it may contain confounds with face-unspecific interference effects. Here we argue that the complete design is well-balanced and allows one to separate face-specific from face-unspecific effects. We used the complete design for a same/different composite stimulus matching task with face and non-face objects (watches). Subjects performed the task with and without trial-by-trial feedback, and with low and high certainty about the target half. Results showed large congruency effects for faces, particularly when subjects were informed late in the trial about which face halves had to be matched. Analysis of response bias revealed that subjects preferred the “different” response in incongruent trials, which is expected when upper and lower face halves are integrated perceptually at the encoding stage. The results pattern was observed in the absence of feedback, while providing feedback generally attenuated the congruency effect, and led to an avoidance of response bias. For watches no or marginal congruency effects and a moderate global “same” bias were observed. We conclude that the congruency effect, when complemented by an evaluation of response bias, is a valid hallmark of feature integration that allows one to separate faces from non-face objects.

Does matching of internal and external facial features depend on orientation and viewpoint

Although it is recognized that external (hair, head and face outline, ears) and internal (eyes, eyebrows, nose, mouth) features contribute differently to face recognition it is unclear whether both feature classes predominantly stimulate different sensory pathways. We employed a sequential speed-matching task to study face perception with internal and external features in the context of intact faces, and at two levels of contextual congruency. Both internal and external features were matched faster and more accurately in the context of totally congruent/incongruent facial stimuli compared to just featurally congruent/incongruent faces. Matching of totally congruent/incongruent faces was not affected by the matching criteria, but was strongly modulated by orientation and viewpoint. On the contrary, matching of just featurally congruent/incongruent faces was found to depend on the feature class to be attended, with strong effects of orientation and viewpoint only for matching of internal features, but not of external features. The data support the notion that different processing mechanisms are involved for both feature types, with internal features being handled by configuration sensitive mechanisms whereas featural processing modes dominate when external features are the focus.

Development of Visual Systems for Faces and Objects: Further Evidence for Prolonged Development of the Face System

Background The development of face and object processing has attracted much attention; however, studies that directly compare processing of both visual categories across age are rare. In the present study, we compared the developmental trajectories of face and object processing in younger children (8–10 years), older children (11–13 years), adolescents (14–16 years), and adults (20–37). Methodology/Principal Findings We used a congruency paradigm in which subjects compared the internal features of two stimuli, while the (unattended) external features either agreed or disagreed independent of the identity of the internal features. We found a continuous increase in matching accuracy for faces and watches across childhood and adolescence, with different magnitudes for both visual categories. In watch perception, adult levels were reached at the age of 14–16, but not in face perception. The effect of context and inversion, as measures of holistic and configural processing, were clearly restricted to faces in all age groups. This finding suggests that different mechanisms are involved in face and object perception at any age tested. Moreover, the modulation of context and inversion effects by exposure duration was strongly age-dependent, with the strongest age-related differences found for brief timings below 140 ms. Conclusions/Significance The results of the present study suggest prolonged development of face-specific processing up to young adulthood. The improvement in face processing is qualitatively different from the improvement of general perceptual and cognitive ability.

The preview benefit for familiar and unfamiliar faces

Previewing distracters improves visual search - the preview benefit (Watson & Humphreys, 1997). Recent fMRI evidence suggests that the preview benefit rests on active inhibition in brain regions concerned with spatial memory, as well as in content selective areas (Allen, Humphreys, & Matthews, 2008). Using familiar and unfamiliar faces in a preview search task we show that search performance is much better with familiar than with unfamiliar faces. With both types of stimuli we obtained preview benefits of at least 10%, measured in terms of the advantage in reaction time relative to the no preview condition. The preview benefit increased up to 30% when distracter faces and their locations were previewed, compared to a benefit in the range of 10-25% for previewing just distracter locations. Analysis in terms of search time per item showed that familiar faces were processed with more than double the efficiency of the unfamiliar faces. Further, efficiency was enhanced relative to the no preview condition only when distracter locations and content were previewed, but not when participants previewed just distracter locations. These findings corroborate that the preview benefit involves both spatial and content-specific mechanisms, and indicate contribution of existing long-term memory representations independent of spatial memory.

The time course of face matching for featural and relational image manipulations.

It was found recently that horizontal and vertical relationships of facial features are differently vulnerable to inversion (Goffaux & Rossion, 2007). When faces are upside down manipulations of vertical relations are difficult to detect, while only moderate performance deficits are found for manipulations of horizontal relations, or when features differ. We replicate the findings of Goffaux and Rossion, and record the temporal courses of face matching performance and the effects of inversion. For vertical relations and featural changes inversion effects arise immediately, starting with the first 50ms of processing. For horizontal relations inversion effects are absent at brief timings, but arise later, after about 200ms. The final magnitudes of inversion effects are different in all three conditions, reaching 23.4% for vertical displacement, 10.7% for feature replacement, and 5.8% for horizontal displacement. Our results underline the special status of horizontal in contrast to vertical feature relations, and indicate that local and global configural information is handled in parallel by specific routines, as proposed recently (Senunkova & Barton, 2008).

From development to aging: Holistic face perception in children, younger and older adults

Few published reports examine the development of holistic face processing across the lifespan such that face-specific processes are adequately differentiated from general developmental effects. To address this gap in the literature, we used the complete design of the composite paradigm (Richler & Gauthier, 2014) with faces and non-face control objects (watches) to investigate holistic processing in children (8-10years), young adults (20-32years) and older adults (65-78years). Several modifications to past research designs were introduced to improve the ability to draw conclusions about the development of holistic processing in terms of face-specificity, response bias, and age-related differences in attention. Attentional focus (narrow vs. wide focus at study) influenced the magnitude of the composite effect without eliminating holistic face processing in all age groups. Young adults showed large composite effects for faces, but none for watches. In contrast, older adults and children showed composite effects for both faces and watches, although the effects for faces were larger. Our findings suggest that holistic processing, as measured by the composite effect, might be moderated by less efficient attentional control in children and older adults. The study also underscores the importance of including comparable complex objects when investigating face processing across the lifespan.