What’s special about personally familiar faces? A multimodal approach GRIT HERZMANN, a STEFAN R. SCHWEINBERGER, b WERNER SOMMER, a and INES JENTZSCH c a Department of Psychology, Humboldt-University at Berlin, Berlin, Germany b Department of Psychology,University of Glasgow, Glasgow, UK c School of Psychology,University of St. Andrews, St. Andrews, UK Abstract Dual-route models of face recognition suggest separate cognitive and affective routes. The predictions of these models were assessed in recognition tasks with unfamiliar, famous, and personally familiar faces. Whereas larger autonomic responses were only triggered for personally familiar faces, priming effects in reaction times to these faces, presumably reflecting cognitive recognition processes, were equal to those of famous faces. Activation of stored structural rep- resentations of familiar faces (face recognition units) was assessed by recording the N250r component in event-related brain potentials. Face recognition unit activation increased from unfamiliar over famous to personally familiar faces, suggesting that there are stronger representations for personally familiar than for famous faces. Because the topog- raphies of the N250r for personally and famous faces were indistinguishable, a similar network of face recognition units can be assumed for both types of faces. Descriptors: Face recognition models, Skin conductance responses, Event-related brain potentials, Priming, Personally known faces Human faces are outstandingly rich sources of information for social interaction, providing detailed information about famil- iarity, identity, mood, gender, age, or focus of attention. It is therefore hardly surprising that the issues of how the cognitive system accomplishes and how the brain implements these aspects of face perception have enjoyed a great deal of scientific interest. Traditional models of face recognition (Bruce & Young, 1986; Hay & Young, 1982) have focused mainly on cognitive processes. However, more recent models (Breen, Caine, & Coltheart, 2000; Ellis & Lewis, 2001) have included affective aspects of face rec- ognition as well. These models suggest that a so-called cognitive route analyzes the identity of faces and provides access to se- mantic knowledge and name of familiar persons. In addition, a second route is thought to be involved in the production of af- fective responses to familiar faces. The assumption of these dis- tinct routes in face processing was made in order to explain impairments of face recognition in prosopagnosia and its sup- posed counterpart, Capgras delusion. Patients with prosopagnosia are unable to identify the faces of familiar persons and to learn new faces. Typically, prosopagnosia is a consequence of acquired brain damage, involving inferior occipito-temporal lesions of the right or both hemispheres. These patients often remain able to recognize familiar persons by voice or gait, and may also show preserved semantic memory for peo- ple, for example, when confronted with their names. Neverthe- less, prosopagnosic patients may be unable to recognize faces of even highly familiar people. However, such faces, even though overtly unrecognized, may elicit signs of covert recognition, such as skin conductance responses (SCR). For example, Bauer (1984) presented the prosopagnosic patient LF with familiar faces, paired with spoken names, which could or could not cor- respond to the face. Although LF could not identify the correct names, his SCRs were larger to correct than incorrect face/name pairs. In other studies, prosopagnosic patients showed larger SCRs to familiar as compared to unfamiliar faces in the absence of overt recognition (Tranel & Damasio, 1985). In terms of dual- route models, preserved differential SCRs may indicate that some patients with prosopagnosia, although impaired in overt recognition along the cognitive route of face recognition, still have a relatively intact affective route. Patients with Capgras delusion show a pattern of impairment that appears to be almost the mirror image of prosopagnosia (Ellis & Young, 1990). Capgras delusion may occur in the context This research was supported by a Socrates-Erasmus exchange stu- dentship to G.H. while she was visiting Glasgow, by a grant by the Deutsche Forschungsgemeinschaft (So 177/14-1) to W.S., and by grants by the Biotechnology and Biological Sciences Research Council (17/ S14233) and the Royal Society to S.R.S. Address reprint requests to: Grit Herzmann, Department of Psy- chology, Humboldt-University at Berlin, Rudower Chaussee 18, D- 10099 Berlin, Germany. E-mail: [email protected], or to Stefan R. Schweinberger, Department of Psychology, University of Glasgow, Glasgow G12 8QQ, Scotland. E-mail: s.schweinberger@psy. gla.ac.uk. Psychophysiology, 41 (2004), 688–701. Blackwell Publishing Inc. Printed in the USA. Copyright r 2004 Society for Psychophysiological Research DOI: 10.1111/j.1469-8986.2004.00196.x 688
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What’s special about personally familiar faces?
A multimodal approach
GRIT HERZMANN,a STEFAN R. SCHWEINBERGER,b WERNER SOMMER,a and INESJENTZSCHc
aDepartment of Psychology, Humboldt-University at Berlin, Berlin, GermanybDepartment of Psychology,University of Glasgow, Glasgow, UKcSchool of Psychology,University of St. Andrews, St. Andrews, UK
Abstract
Dual-route models of face recognition suggest separate cognitive and affective routes. The predictions of these models
were assessed in recognition tasks with unfamiliar, famous, and personally familiar faces. Whereas larger autonomic
responses were only triggered for personally familiar faces, priming effects in reaction times to these faces, presumably
reflecting cognitive recognition processes, were equal to those of famous faces. Activation of stored structural rep-
resentations of familiar faces (face recognition units) was assessed by recording the N250r component in event-related
brain potentials. Face recognition unit activation increased from unfamiliar over famous to personally familiar faces,
suggesting that there are stronger representations for personally familiar than for famous faces. Because the topog-
raphies of theN250r for personally and famous faces were indistinguishable, a similar network of face recognition units
Human faces are outstandingly rich sources of information for
social interaction, providing detailed information about famil-
iarity, identity, mood, gender, age, or focus of attention. It is
therefore hardly surprising that the issues of how the cognitive
system accomplishes and how the brain implements these aspects
of face perception have enjoyed a great deal of scientific interest.
Traditional models of face recognition (Bruce & Young, 1986;
Hay&Young, 1982) have focusedmainly on cognitive processes.
However, more recent models (Breen, Caine, & Coltheart, 2000;
Ellis & Lewis, 2001) have included affective aspects of face rec-
ognition as well. These models suggest that a so-called cognitive
route analyzes the identity of faces and provides access to se-
mantic knowledge and name of familiar persons. In addition, a
second route is thought to be involved in the production of af-
fective responses to familiar faces. The assumption of these dis-
tinct routes in face processing was made in order to explain
impairments of face recognition in prosopagnosia and its sup-
posed counterpart, Capgras delusion.
Patients with prosopagnosia are unable to identify the faces of
familiar persons and to learn new faces. Typically, prosopagnosia
is a consequence of acquired brain damage, involving inferior
occipito-temporal lesions of the right or both hemispheres. These
patients often remain able to recognize familiar persons by voice
or gait, and may also show preserved semantic memory for peo-
ple, for example, when confronted with their names. Neverthe-
less, prosopagnosic patients may be unable to recognize faces of
even highly familiar people. However, such faces, even though
overtly unrecognized, may elicit signs of covert recognition, such
as skin conductance responses (SCR). For example, Bauer
(1984) presented the prosopagnosic patient LF with familiar
faces, paired with spoken names, which could or could not cor-
respond to the face. Although LF could not identify the correct
names, his SCRs were larger to correct than incorrect face/name
pairs. In other studies, prosopagnosic patients showed larger
SCRs to familiar as compared to unfamiliar faces in the absence
of overt recognition (Tranel & Damasio, 1985). In terms of dual-
route models, preserved differential SCRs may indicate that
some patients with prosopagnosia, although impaired in overt
recognition along the cognitive route of face recognition, still
have a relatively intact affective route.
Patients with Capgras delusion show a pattern of impairment
that appears to be almost the mirror image of prosopagnosia
(Ellis&Young, 1990). Capgras delusionmay occur in the context
This research was supported by a Socrates-Erasmus exchange stu-
dentship to G.H. while she was visiting Glasgow, by a grant by the
Deutsche Forschungsgemeinschaft (So 177/14-1) to W.S., and by grants
by the Biotechnology and Biological Sciences Research Council (17/
S14233) and the Royal Society to S.R.S.Address reprint requests to: Grit Herzmann, Department of Psy-
chology, Humboldt-University at Berlin, Rudower Chaussee 18, D-10099 Berlin, Germany. E-mail: [email protected], or toStefan R. Schweinberger, Department of Psychology, University ofGlasgow, Glasgow G12 8QQ, Scotland. E-mail: [email protected].
Psychophysiology, 41 (2004), 688–701. Blackwell Publishing Inc. Printed in the USA.Copyright r 2004 Society for Psychophysiological ResearchDOI: 10.1111/j.1469-8986.2004.00196.x
688
of psychiatric conditions or as a result of structural or toxic brain
damage. Although these patients are still able to identify familiar
faces, they lack a sense of familiarity to these faces and believe
that impostors, doubles, or aliens have replaced these people
(e.g., spouses or children). Ellis and Young proposed that Cap-
gras patients, though unimpaired in their cognitive route for face
recognition, might have a damaged affective route. Their pre-
diction that these patients would fail to produce a differential
SCR response to overtly recognized familiar faces was confirmed
by subsequent research (Ellis, Young, Quayle, & DePauw, 1997;
Hirstein & Ramachandran, 1997).
The dissociation of autonomic responses and overt face rec-
ognition in prosopagnosia and Capgras delusion was taken as
support for the existence of two routes to face recognition. Bauer
(1984) postulated two routes for face recognition in both neuro-
anatomical and functional terms. A ventral visual-limbic route in
inferior temporal cortex was suggested to mediate overt identi-
fication and to be impaired in prosopagnosia. A dorsal route
projecting from primary visual cortex to limbic structures via the
superior temporal sulcus and inferior parietal lobe was consid-
ered to be involved in the detection of emotional significance and
to mediate the preserved SCR responses in prosopagnosic pa-
tients. Ellis and Young (1990) adopted Bauer’s dual-route model
to accommodate Capgras delusion, which was considered to be
the consequence of damage in the affective route, as indicated by
the absence of SCRs to familiar faces (Ellis et al., 1997).
The theories of both Bauer (1984) and Ellis andYoung (1990)
claim that a face has to be identified to some degree before its
relevance for affective responses can be noticed. In terms of cur-
rent concepts about face recognition (e.g., Bruce &Young, 1986)
these models therefore make the implicit assumption of two in-
dependent sets of stored representations of familiar faces (face
recognition units) feeding into the affective and the cognitive
routes. Recently, Breen et al. (2000) pointed out that Bauer’s
model does not specify possible mechanisms for face recognition
in the dorsal route and noted that there is little evidence for object
or face recognition in this route (Ungerleider & Mishkin, 1982).
Therefore, Breen et al. made the more parsimonious suggestion
of one common pool of FRUs residing within the ventral visual
stream and feeding into both the cognitive and affective routes.
Breen et al. adapted the face recognition model of Bruce and
Young, which contains only a singleFcognitiveFroute, by
adding a module triggering affective responses to familiar faces.
In the modified model, face recognition units feed information
simultaneously and independently into both person identity
nodes and the affective module. Face recognition is thought to
take place along an anatomical route in ventral temporal lobe
structures, with the amygdala triggering affective responses to
familiar faces. Within this framework, Breen et al. explained the
dissociation between patients with prosopagnosia and Capgras
delusion. Prosopagnosia can be caused by an impaired connec-
tion between the face recognition units and the person identity
nodes, while the connection between the face recognition units
and the affective response module may be intact. In contrast, the
locus of impairment in Capgras delusion is either within the af-
fective module or in the connection between the face recognition
units and the affective module (see Figure 1). Subsequently, Ellis
and Lewis (2001) slightlymodified the dual-routemodel of Breen
et al. by adding an integrative device, which compares the out-
puts of the affective and cognitive routes. This was done to ex-
plain the delusion inCapgras patients when a familiar face fails to
elicit a corresponding affective response.
Taken together, all models of face recognition that attempt to
encompass both findings in prosopagnosia and Capgras delusion
and differences between overt and covert face recognition (Ba-
1Although not all participants from the SCR study were available forthe ERP study, the results in Part 1 of the experiment were essentiallyunchanged even when only these 16 participants were considered.
In the unprimed condition, personally familiar and famous target
faces were preceded by unfamiliar primes, and unfamiliar target
faces were preceded by personally familiar or famous primes.
This allowed us to test repetition priming for both familiar and
unfamiliar targets without an impractically large amount of filler
trials and appeared appropriate because previous research
(Schweinberger et al., 1995) had indicated that responses to un-
primed target faces are independent of whether or not the pre-
ceding prime face is familiar.
The design involved the variables priming (primed vs. un-
primed) and familiarity (personally familiar, famous, and unfa-
miliar). Each of the 60 target faces appeared three times in the
primed condition and three times in the unprimed condition,
yielding a total of 360 experimental trials. In the unprimed con-
dition a given pair of faces was used only once in order to avoid
episodic priming. All trials were shown in randomized order.
Recording
The electroencephalogram (EEG) was recorded with sintered
Ag/AgCl electrodes mounted in an electrode cap (Easy-Capt) at
2It is interesting that the observation of higher percentages of errors isin contrast with the finding of larger SCRs to personally familiar thanfamous faces. This would seem to exclude an explanation of the SCReffect in terms of overall better knowledge of personally familiar faces.
3Several studies (Bentin &Deouell, 2000; Eimer, 2000) have indicatedthat the N170 is insensitive to the familiarity of faces. Similarly, althoughthere are several studies that report face repetition effects for the N170 oreven earlier components (e.g., Braeutigam, Bailey, & Swithenby, 2001),one difficulty with these effects is that they appear to be rather incon-sistent across studies. Although we would not completely reject the pos-sibility that there may be small repetition effects on the N170, the presenteffects in this time range might also reflect temporal overlap with therising slope of the N250r, rather than differences in the N170 itself.
of familiarity, Fs(58,870)5 6.1 and 7.3, pso.001, es5 .20 and
.17, and significant interactions between priming and familiarity,
Fs(58,870)5 3.5 and 6.6, pso.001, es5 .16. Pairwise compari-
sons revealed significant priming effects at each level of famil-
iarity, all Fs(29,435)44.5, all ps o.01, all eso.19. Moreover,
priming effects in both time segments differed between personally
familiar and famous faces, Fs(29,435)5 5.0 and 4.3, po.001 and
po.01, es5 .28 and .18, respectively, and also between person-
ally familiar and unfamiliar faces, Fs(29,435)5 4.9 and 12.4,
pso.001, es5 .18 and .20, respectively. In contrast, priming ef-
fects differed between famous and unfamiliar faces in the 270–
330 ms segment, F(29,435)5 3.2, po.05, e5 .14, but not in the
preceding 230–270-ms segment, Fo1. It may be noted that in
both segments there were also significant familiarity-induced
modulations of amplitude for unprimed faces, Fs(29,435)5 5.2
and 4.0, pso.001, es5 .19 and .20. Bonferoni-corrected pairwise
comparison within the unprimed condition revealed significant
differences in amplitude between all familiarity conditions at the
230–270-ms segment, Fs(29,435)44.4, pso.01, eso.23. In the
270–330-ms time segment amplitudes differed significantly only
between personally familiar and unfamiliar, F(29,435)5 4.8,
po.001, eo.24, as well as between famous and unfamiliar faces,
e5 1.13, and a trend for an interaction of priming and famili-
arity, F(2,30)5 2.6, p5 .10, e5 .81. This interaction was due to
priming effect differences between personally familiar and fa-
mous faces, F(1,15)5 7.5, po.05, but not for the other famil-
iarity comparisons, Fs(1,15)o1.7. In the same time segment,
temporal electrodes only revealed significant main effects of
priming, F(1,15)5 68.2, po.001, and familiarity, F(2,30)5
15.5, po.001, e5 .91, but no differences in priming effects
across familiarity conditions, F(2,30)5 1.6, p5 .22, e5 .95.
In the 270–330-ms segment the ROI analysis revealed similar
effects. At both frontal and temporal electrode sites the main
effects of priming and familiarity reached significance, pso.001.
Moreover, there was a significant interaction of familiarity and
priming at frontal electrodes, F(2,30)5 3.9, p5 .05, e5 .93, this
interaction again arising from priming effect differences between
personally familiar and famous faces, F(1,15)5 7.1, po.05.
Again, no significant interaction showed up at temporal elec-
trode sites, F(2,30)5 1.8, p5 .19, e5 .97.
To address the question of whether or not these data provide
evidence for separate face recognition units for the affective and
cognitive routes, the topographies of the N250r for each category
of facial familiarity were analyzed. If scalp topographies of the
N250r differ, one may conclude that at least some of the gen-
erator sources of this effect are different, lending support for the
idea of separate N250r. Interactions in ERP amplitudes of ex-
perimental variables with electrode site may derive from differ-
ences in the underlying neuronal source configuration only when
differences in source strength are ruled out. Therefore, ANOVAs
were calculated with factors familiarity and electrode site for the
N250r after scaling them to the same overall amplitude within
each condition with the average distance of the mean, derived
from the grand mean ERPs, as the divisor (McCarthy & Wood,
What’s special about personally familiar faces? 695
Figure 3. ERPs recorded for primed (solid lines) and unprimed (dashed lines) personally familiar target faces. Recordings are shown
for all 30 channels. Arrows indicate the P1, N170, the early repetition effect (N250r), and the late repetition effect (N400).
4The observed familiarity effects within the unprimed condition weresignificant but weaker than the N250r effect and showed a different to-pography. They appear to originate from a different source, and willtherefore not be analyzed any further.
1985). Recently, Urbach and Kutas (2002) criticized this proce-
dure as being potentially unreliable in its intended application of
identifying generator differences, particularly when overall base-
line differences exist between conditions, or whenmultiple sourc-
es are present simultaneously. In our experience, overall baseline
differences are not likely to be a strong concern in the present
study, which used average reference such that any overall dif-
ferences should be eliminated. In addition, dipole source local-
ization of theN250r to famous faces has suggested a single source
in the fusiform gyrus (Schweinberger, Pickering, Jentzsch, et al.,
2002). Nevertheless, when using scaling to investigate differences
in underlying neuronal source configuration, potential limita-
tions of this procedure should be kept in mind.
N250r topographies of priming effects differed significantly
across familiarity conditions in the 270–330-ms segment,
F(58,870)5 4.8, po.001, e5 .14. Figure 6 suggests that the pos-
itive aspect of the N250r peaked in midfrontal regions for un-
familiar faces, but for personally familiar and famous faces it was
more pronounced in more posterior central regions. Pairwise
comparisons confirmed differences in topography between un-
familiar and both personally familiar faces, F(29,435)5 9.0,
po.001, e5 .18, and famous faces, F(29,435)5 3.4, po.05,
e5 .17. However, N250r topographies for personally familiar
and famous faces were indistinguishable, F(29,435)5 2.5,
p4.10, e5 .14.
N400 (late repetition effect). In both the 330–400-ms and the
400–500-ms segment there were significant effects of priming,
Fs(29,435)5 22.6 and 5.0, po.001 and po.01, es5 .17 and .15,
of familiarity, Fs(58,870)5 4.1 and 2.6, pso.001, es5 .19 and
.17, and of their interactions, Fs(58,870)5 9.0 and 2.0, po.001
and po.05, es5 .18, respectively. These priming effects resemble
an N400-like modulation of the late positive complex, with more
negativity (or less positivity) for unprimed than primed faces at
central-parietal locations, and less negativity at prefrontal and
lateral frontal locations (see Figures 3–5). Furthermore, Figure 5
suggests that between 330 and 400 ms the N400 priming effect
(i.e., the difference between primed and unprimed faces) in-
creased in amplitude from unfamiliar over famous to personally
familiar faces. In the 330–400-ms segment, priming was signif-
icant at each level of familiarity, Fs(29,435)44.6, pso.001,
es5 .19. Post hoc comparisons showed differences in the N400
696 G. Herzmann et al.
Figure 4. ERPs for personally familiar (first column), famous (second column), and unfamiliar target faces (third column)
comparing primed (solid lines) and unprimed conditions (dashed lines) at themost important electrode sites (Pz, Fz, TP10, and P10).
Vertical timelines indicate the areas of the early repetition effect, which were used in the ANOVA (230–270 ms and 270–330 ms).
priming effect between personally familiar and famous,
F(29,435)5 3.7, p5 .01, e5 .27, personally familiar and unfa-
miliar, F(29,435)5 15.3, p5 .001, e5 .21, and between famous
and unfamiliar faces, F(29,435)5 6.2, p5 .001, e5 .16. In the
400–500-ms segment, priming was significant for personally
familiar, F(29,435)5 4.9, po.001, e5 .20, and famous faces,
F(29,435)5 3.5, po.05, e5 .17, but was reduced to insignifi-
cance for unfamiliar faces,F(29,435)5 2.7, p4.10, e5 .10. ROIs
analysis of the 330–400-ms time segment revealed significant
main effects of priming, F(1,15)5 58.2, p5 .001, and familiarity,
F(2,30)5 8.8, p5 .001, e5 1.15, as well as an interaction be-
tween priming and familiarity at central-parietal electrodes,
Decisions about the familiarity of a face are supposed to be
made at the person identity node level (Burton et al., 1999).
Repetition priming has been proposed to involve processing fa-
cilitation already during the access to face recognition units or
even structural encoding (Pfutze et al., 2002; Schweinberger et
al., 1995; Schweinberger, Pickering, Jentzsch, et al., 2002). In this
respect, the observed amplitude differences of the N250r for
personally familiar compared with famous or unfamiliar faces
could be a result of more widespread and stronger neural net-
works coding these faces. These network differences might result,
for example, from a more extensive range of visual experience
with personally familiar faces, compared with famous faces.
Stronger networks can be assumed to expedite information
processing by reducing the threshold for face recognition (Mohr
et al., 2002). In contrast to the quantitative differences in N250r
amplitudes, the topographies of N250r for personally familiar
and famous faces were indistinguishable. This is consistent with
What’s special about personally familiar faces? 697
Figure 5. ERP difference waves (primedminus unprimed) for personally
familiar (solid lines), famous (dashed lines), and unfamiliar target faces
(dotted lines) at the most important electrode sites (Pz, Fz, TP10, and
P10). Vertical timelines indicate the areas of the early repetition effect,
which were used in the ANOVA (230–270 ms and 270–330 ms).
the notion of similar underlying neural sources. The only top-
ographical difference found was between the N250r for unfamil-
iar faces and both personally familiar and famous faces, confirm-
ing earlier suggestions of qualitatively different underlyingmech-
anism for unfamiliar faces (Hancock, Bruce, & Burton, 2000).
The present N400 priming effect broadly replicates the N400-
like effect observed before (Bentin & McCarthy, 1994; Schwein-
berger et al., 1995; Schweinberger, Pickering, Burton, et al.,
2002). For the present data, this interpretation must be seen with
some restrictions because the N400 may have been partially in-
fluenced by a latency shift in a late positive ERP component (see
Figures 3 and 4) especially when RTs differed between condi-
tions. In the absence of such RT differences, in the 330–400-ms
segment the N400 priming effect was more pronounced for per-
sonally familiar than for famous faces, as can be seen in Figure 5.
According to network theories of face recognition (Burton et al.,
1999), this could reflect more elaborated semantic processing for
personally familiar than for famous people.
One must be aware that because of the small number of crit-
ical stimuli and of the preceding SCR experiment, each stimulus
was repeated four times across the two experiments. Multiple
repetitions could be assumed to have made the unfamiliar faces
familiar for the participants and consequently may have influ-
ences the RT and ERP results. However, multiple repetitions
were used in all conditions and therefore should not have caused
differences between conditions. In addition, although an influ-
ence of repetitions over longer time intervals is usually found for
N400, N250r reflects a more transient effect and seems to be
insensitive to repetitions over longer intervals (Schweinberger,
Pickering, Burton, et al., 2002).
698 G. Herzmann et al.
Figure 6. Topographical voltage maps of ERP differences between primed and unprimed conditions showing priming effects for
personally familiar (left column), famous (middle), and unfamiliar faces (right column) at different latencies after target
presentation. All maps were obtained by using spherical spline interpolation. Equipotential lines are separated by 1 mV/line;negativity is shaded.
General Discussion
Within the framework of dual-route models (Breen et al., 2000;
Ellis & Lewis, 2001), the present study had two main objectives.
Objective 1
In the present study we explored the effects of three different
types of facial familiarity on affective as well as cognitive aspects
of face recognition, and on the face recognition units, using
SCRs, priming effects, and the N250r.
We found that face familiarity caused different effects in SCRs
and RT priming. Whereas stronger cognitive effects (RT prim-
ing) were elicited by famous than unfamiliar faces, this was not
the case for the autonomic responses (SCR). Strong autonomic
responses were only triggered for personally known faces for
which, however, cognitive activation did not exceed the level
attained for famous faces.
According to dual-route models, the SCR is assumed to rep-
resent the activation within an affective route. However, these
models are not very specific about what is meant with affect: Is it
an emotional response to the familiar face or is it a reflection of
the significance of the displayed person for the observer? It
should also be kept in mind that, although SCRs are a result of
activation of the sympathetic autonomic nervous system, they
are rather unspecific responses, which can be caused by a number
of affective as well as cognitive processes. Therefore, cognitive
components of face processing could, in principle, have contrib-
uted to the observed SCR results.
Electrodermal responses have been suggested to be triggered
by processes such as novelty, emotion, or significance of the
stimulus (e.g., Dawson, Schell, & Filion, 2000). In the setting of
the present study, it is unlikely that novelty has triggered the
obtained results of larger SCRs to personally familiar faces. It
can be assumed that the participants have seen their lecturers as
frequently as or even more often than the shown celebrities and,
of course, also more often than the unfamiliar faces. Because
personally familiar and famous faces were both used as targets
and placed into the same category, they had the same significance
with respect to the task, yet they differed in SCRs. Therefore the
‘‘affective’’ response reflected in the SCRs to personally familiar
faces might relate to emotional responses or to the ‘‘personal
significance’’ for the observer. In principle, it may be possible
that the participants experienced a specific emotional response to
their lecturers as their portraits were shown such as joy, fear, and
so forth. However, to us it seems to be more plausible that the
observed SCRs may reflect the importance or significance of the
portrayed lecturers for our participantsFtheir students. There-
fore, the SCRs may represent the significance of the stimuli as
defined by the personal background of the observer rather than
by the experimental task.
The amplitude of the N250r exhibited reliable quantitative
differences in the face recognition units between all three types of
familiarity. Showing a continuous increase from unfamiliar over
famous to personally known faces, this result could point to the
assumptions of increasing face recognition units strength with
facial familiarity.
It may be argued that lecturers may not be typical instances
for personally familiar people, as might be family members or
friends. Although it would be desirable to replicate the present
findings with these kinds of stimuli, the pictures employed here
did elicit significant effects, especially in the N250r amplitudes,
which are thought to be a sign of stored facial structures. In SCRs
and the N250r, personally familiar faces were found to cause the
largest effects. This can additionally be caused by their high (so-
cial) importance, which lecturers as authorities bear for their
students. These results confirm the notion that personally famil-
iar compared with famous faces encompass especially an advan-
tage in affective aspects of face processing and may have a
stronger network of face recognition units.
Objective 2
We also addressed the question of whether there are unitary or
multiple face recognition mechanisms, or face recognition units,
feeding into the affective and cognitive routes of face processing,
using both functional and neural information of the early rep-
etition effect (N250r).
We found that the N250r, taken to reflect face recognition
unit activation, did not differ in its neural underpinnings between
personally familiar and famous faces. Although a quantitatively
larger N250r was seen for personally familiar faces, the scalp
topographies of the N250r to personally familiar and famous
faces were indistinguishable. Recent brain electric source anal-
yses of the N250r are consistent with a generator in fusiform
gyrus (Schweinberger, Pickering, Jentzsch, et al., 2002), an area
that is strongly implicated in face recognition (Kanwisher,
McDermott, & Chun, 1997) and face repetition priming (Hen-
son, Shallice, & Dolan, 2000).
Before taking this result as evidence for a common face
recognition unit, one needs to be aware of certain limitations of
ERP research. In particular, whereas topographical differences
between two ERPs or ERP effects indicate that these were gen-
erated by at least partially different sources, there might beFat
least in principleFa number of reasons for the absence of such
differences. For an ERP to be recordable at the scalp, simulta-
neous activity of a vast number of suitably aligned neurons is
required. Although this is often the case for cortical sources, it
may not hold true in many subcortical sources (Wood & Allison,
1981). We believe that this problem is unlikely to have biased the
present interpretation, as scalp-recorded ERPs can likely be re-
corded from key structures in the dorsal route, specifically the
superior temporal sulcus (Puce, Smith, & Allison, 2000) and
cingulate gyrus (Badgaiyan & Posner, 1998). However, respons-
es to personally familiar faces along the affective route would
include activity in ventral limbic structures (and amygdala in
particular), and it is well possible that such activitymight bemore
difficult to pick up. Despite these caveats, we would like to em-
phasize that the present ERP data did show topographical dif-
ferences in N250r between unfamiliar faces and both famous and
personally familiar faces. This not only lends support to the idea
that the recognition of familiar and unfamiliar faces is governed
by a qualitatively different mechanism (Hancock et al., 2000), it
also suggests that the equivalence of the topographies for per-
sonally and famous faces is unlikely to be a result of insufficient
power to find such topographical differences in the present ex-
periment.
Using the framework of dual-route models to test the influ-
ence of facial familiarity on face processing reinforced the sug-
gestion that face recognition is the result of the interaction of
several components in the information processing system. In
addition, the results of the study strengthen the notion of one
single set of face recognition units, feeding into both the affective
and cognitive route. The current findings are consistent with the
views of Breen et al. (2000) and Ellis and Lewis (2001) that the
What’s special about personally familiar faces? 699
initial parts of face recognition take place along a single ana-
tomical routeFthe ventral route.
Finally, with the present study we provide insight into the class
of familiar faces by adding findings about personally familiar faces
to the existing results of familiarity-induced effects on SCR, RT
priming, and the N250r. For personally familiar faces, more
widespread and elaborative networks may be assumed for (a)
stored representations of facial structures (face recognition unit),
as indicated by larger effects of the N250r amplitude; and (b)
stored semantic codes, as indicated by a higher amplitude of the
N400. Additionally, these faces are associated with a stronger af-
fective response, as seen in larger SCRs. However, as the topog-
raphies of the N250r to personally familiar and famous faces did
not differ, recognition of both types of familiar faces can be
thought to be triggered essentially by the same neural generator,
most likely the fusiform gyrus (Schweinberger, Pickering,
Jentzsch, et al., 2002).
To conclude, by using a multidimensional methodological
approach we have been able to give a comprehensive insight into
modulations of face recognition by facial familiarity. In partic-
ular, we have provided new evidence that face recognition units
may serve as common modules feeding into both affective and
cognitive routes. The strength of the networks representing face
recognition units appears to increase as a function of the degree
of facial familiarity.
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(Received July 31, 2003; Accepted January 5, 2004)
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