The composite face illusion: A whole window into our understanding of holistic face perception

Two identical top halves of a face are perceived as being different when their bottom halves belong to different faces, showing that the parts of a face cannot be perceived independently from the whole face. When this visual illusion is inserted in a matching task, observers make more mistakes and/or are slower at matching identical top face halves aligned with different bottom halves than when the bottom halves are spatially offset: The composite face effect. This composite face paradigm has been used in more than 60 studies that have provided information about the specificity and nature of perceptual integration between facial parts (“holistic face perception”), the impairment of this process in acquired prosopagnosia, its developmental course, temporal dynamics, and neural basis. Following a review of the main contributions made with the paradigm, I explain its rationale and strengths, and discuss its methodological parameters, making a number of proposals for its optimal use and refinement in order to improve our understanding of holistic face perception. Finally, I explain how this standard composite face paradigm is fundamentally different than the application to facial parts of a congruency/interference paradigm that has a long tradition in experimental psychology since Stroop (1935), and which was originally developed to measure attentional and response interference between different representations rather than perceptual integration. Moreover, a version of this congruency/interference paradigm used extensively over the past years with composite faces lacks a baseline measure and has decisional, attentional, and stimulus confounds, making the findings of these studies impossible to interpret in terms of holistic perception. I conclude by encouraging researchers in this field to concentrate fully on the standard composite face paradigm, gaze contingency, and other behavioural measures that can help us take one of the most important challenges of visual perception research: Understanding the neural mechanisms of holistic face perception.     

Holistic face perception: Mind the gap!

The most widely used measurement of holistic face perception, the composite face effect (CFE), is challenged by two apparently contradictory goals: having a defined face part (i.e., the top half), and yet perceiving the face as an integrated unit (i.e., holistically). Here, we investigated the impact of a small gap between top and bottom face halves in the standard composite face paradigm, requiring matching of sequentially presented top face halves. In Experiment 1, the CFE was larger for no-gap than gap stimuli overall, but not for participants who were presented with gap stimuli first, suggesting that the area of the top face half was unknown without a gap. This was confirmed in Experiment 2, in which these two stimulus sets were mixed up: the gap stimuli thus provided information about the area of a top face half and the magnitude of the CFE did not differ between stimulus sets. These observations indicate that the CFE might be artificially inflated in the absence of a stimulus cue that objectively defines a border between the face halves. Finally, in Experiment 3, observers were asked to determine which of two simultaneously presented faces was the composite face. Perceptual judgements for no-gap stimuli approached ceiling; however, with a gap, participants were almost unable to distinguish the composite face from a veridical face. This effect was not only due to low-level segmentation cues at the border of no-gap face halves, because stimulus inversion decreased performance in both conditions. This result indicates that the two halves of different faces may be integrated more naturally with a small gap that eliminates an enhanced contrast border. Collectively, these observations suggest that a small gap between face halves provides an objective definition of the face half to match and is beneficial for valid measurement of the behavioural CFE.     

Left–right holistic integration of human bodies

Holistic integration of faces has been widely studied. More recently, investigations have explored whether similar processing is used for human bodies. Here we show that holistic processing, as measured by the composite task, does occur for bodies but is stronger for left and right halves than for top and bottom halves. We also found composite effects for left–right halves of inverted bodies. Standard composite effects were found for top halves of faces, tested as a control. We argue that our results suggest that holistic processing of faces and bodies might not exclusively occur for identification, but instead may also have evolved to aid communication and/or decisions about mate choice (through judging symmetry).     

Cohésion–non-cohésion des scores composites : valeurs seuils et interprétabilité. L’exemple du WISC-IV

When interpreting the composite scores of the Wechsler Intelligence scales, some authors recommended to determine whether the composite scores are unitary or not. It has been suggested that when variability among scores is too large, then the composite score does not provide a good estimate of the psychological attribute, and is not interpretable. The first objective of the paper is to demonstrate that the cut-off threshold values (23 points and 5 points) proposed by some authors are inadequate. Other cut-off threshold values should be used. Most importantly, the second goal of this paper is to demonstrate that the notion of unitary abilities that was guiding principle of interpretation is also inadequate. Indeed, nonunitary index still provides relevant information.     

Holistic face processing is mature at 4 years of age: evidence from the composite face effect

Although it is acknowledged that adults integrate features into a representation of the whole face, there is still some disagreement about the onset and developmental course of holistic face processing. We tested adults and children from 4 to 6 years of age with the same paradigm measuring holistic face processing through an adaptation of the composite face effect [Young, A. W., Hellawell, D., & Hay, D. C. (1987). Configurational information in face perception. Perception, 16, 747-759]. In Experiment 1, only 6-year-old children and adults tended to perceive the two identical top parts as different, suggesting that holistic face processing emerged at 6 years of age. However, Experiment 2 suggested that these results could be due to a response bias in children that was cancelled out by always presenting two faces in the same format on each trial. In this condition, all age groups present strong composite face effects, suggesting that holistic face processing is mature as early as after 4 years of experience with faces.     

Hemisphere-dependent holistic processing of familiar faces

In two behavioral experiments involving lateralized stimulus presentation, we tested whether one of the most commonly used measures of holistic face processing—the composite face effect—would be more pronounced for stimuli presented to the right as compared to the left hemisphere. In experiment 1, we investigated the composite face effect in a verbal identification task, similar to its original report (Young, Hellawell, & Hay, 1987). Aligning top and bottom halves of composite face stimuli led to performance decreases irrespective of hemifield, indicating holistic processing of comparable magnitude for inputs provided separately to either hemisphere. However, when matching of the same top parts was required in experiment 2, an alignment-dependent performance decrease was found for stimuli presented in the left, but not right visual field. These observations suggest that the right hemisphere dominates in early stages of holistic processing, as indexed by the composite face effect, but that later processes such as face identification and naming are based on unified representations that are independent of input lateralization. Moreover, the composite face effect may not rely on the exact same representation(s) when measured in matching and identification tasks.     

Thermal behaviour of poly(methyl methacrylate)/fullerene composite films

ABSTRACT

Poly(methyl methacrylate) films and poly(methyl methacrylate)/fullerene composite films were fabricated by casting from toluene solutions. The mass fraction of fullerene (C₆₀) was varied from 0.05–3?wt. %. The effect of the fullerene (C₆₀) content on the thermal degradation parameters of the composite films was evaluated by thermogravimetric (TG) analysis. It was found that the incorporation of C₆₀ improved the thermal stability of the polymers. The films eventually decomposed in three stages. Incorporation of fullerene caused a change in the distribution of mass loss over the stages of degradation in comparison with the pristine polymer. Using differential scanning calorimetry (DSC), the phase transitions from the glassy state to the elastic one was studied for the examined polymeric materials. New data relating to the effect of C₆₀ on the glass transition temperature of composites with low weight fractions of filler were obtained. Specifically, for films containing up to 0.1 wt. % of C₆₀, a single glass transition temperature was found, whereas for composites with a higher concentration of filler, two glass transition temperatures were recorded.     

Identity specific adaptation with composite faces

A composite face, made from the top half of a celebrity face and the bottom half of an unfamiliar face, appears to be a single, “new” face (e.g., Young, Hellawell, & Hay, 1987). Composite faces were used within the face identity aftereffect (FIAE) paradigm, in which prolonged exposure to a face reduces sensitivity to it (adaptation). Adaptation occurred both with an intact face and with composites containing its upper half, but only when composites were explicitly recognized during the adaptation phase. Unrecognized composites produced no adaptation. These findings imply that the FIAE is a relatively high-level perceptual effect, given that identical stimuli either did or did not produce adaptation depending on whether or not they were recognized. They also suggest a perceptual locus for the “composite face effect”.     

重估测谎决策的Bayes推断试验

谎与非谎的情绪反应没有独立的客观标准,以Polygrapy构成技术的测谎缺乏稳定的效度。本研究尝试运用Bayes方法分析一项实测案例,计算两名被试的低显性测谎反应结果,使准确判决有谎的概率由机会水平50％分别调整到可明确分辩的74％和49％,从决策分析角度为改良测谎程序和提高测谎效率提供了一种新的操作思路。