Repetition priming of face recognition

Three experiments investigating the priming of the recognition of familiar faces are reported. In Experiment 1, recognizing the face of a celebrity in an “Is this face familiar?” task was primed by exposure several minutes earlier to a different photograph of the same person, but not by exposure to the person's written name (a partial replication of Bruce and Valentine, 1985). In Experiment 2, recognizing the face of a personal acquaintance was again primed by recognizing a different photograph of their face, but not by recognizing the acquaintance from that person's body shape, clothes etc. Experiment 3 showed that maximum repetition priming is obtained from prior exposure to an identical photograph of a famous face, less from a similar photograph, and least (but still significant) from a dissimilar photograph.

We argue that repetition priming is a function of the degree of physical similarity between two stimuli and that lack of priming between different stimulus types (e.g., written names and faces, or bodies and faces) may be attributable to lack of physical similarity between prime and test stimuli. Repetition priming effects may be best explained by some form of “instance-based” model such as that proposed by McClelland and Rumelhart (1985).     

Repetition Priming Follows Spontaneous but not Prompted Recognition of Familiar Faces

Reaction times to make a familiarity decision to the faces of famous people were measured after recognition of the faces in a pre-training phase had occurred spontaneously or following prompting with a name or other cue. At test, reaction times to familiar faces that had been recognized spontaneously in the pre-training phase were significantly facilitated relative to an unprimed comparison condition. Reaction times to familiar faces recognized only after prompting in the pre-training phase were not significantly facilitated. This was demonstrated both when a name prompt was used (Experiments 1 and 3) and when subjects were cued with brief semantic information (Experiment 2).

Repetition priming was not found to depend on prior spontaneous recognition per se. In Experiment 3, spontaneously recognizing a familiar face did not prime subsequent familiarity judgements when the same face had only been identified following prompting on a prior encounter. In Experiment 4, recognition memory for faces recognized after cueing was found to be over 90% accurate. This indicates that prompted recognition does not yield repetition priming, even though subjects can remember the faces. A fusion of “face recognition unit” and “episodic record” accounts of the repetition priming effect may be more useful than either theory alone in explaining these results.     

The role of familiarity in a face classification task using thatcherized faces

Two experiments are reported to test the proposition that facial familiarity influences processing on a face classification task. Thatcherization was used to generate distorted versions of familiar and unfamiliar individuals. Using both a 2AFC (which is “odd”?) task to pairs of images (Experiment 1) and an “odd/normal” task to single images (Experiment 2), results were consistent and indicated that familiarity with the target face facilitated the face classification decision. These results accord with the proposal that familiarity influences the early visual processing of faces. Results are evaluated with respect to four theoretical developments of Valentine's (1991) face-space model, and can be accommodated with the two models that assume familiarity to be encoded within a region of face space.     

Repetition priming of face gender judgments: An instance based explanation

Earlier studies of repetition priming using faces have been interpreted as indicating that such effects are confined to the processing of known faces. The experiment reported here employed eight rather than the more usual two presentation trials and required subjects to make gender decisions (is it a male or is it a female face?) to both familiar and unfamiliar faces. This allowed the currently favored recognition unit theories of face processing to be compared with the Logan (1988) instance model. Equivalent repetition priming effects were observed for both familiar and unfamiliar faces and were well fitted by power functions. It is argued that the findings are consistent with the strong predictions made by Logan's model and pose problems for recognition unit based theories.     

Repetition priming of face gender judgments: An instance based explanation

Earlier studies of repetition priming using faces have been interpreted as indicating that such effects are confined to the processing of known faces. The experiment reported here employed eight rather than the more usual two presentation trials and required subjects to make gender decisions (is it a male or is it a female face?) to both familiar and unfamiliar faces. This allowed the currently favored recognition unit theories of face processing to be compared with the Logan (1988) instance model. Equivalent repetition priming effects were observed for both familiar and unfamiliar faces and were well fitted by power functions. It is argued that the findings are consistent with the strong predictions made by Logan's model and pose problems for recognition unit based theories.     

Haven't we met before? The effect of facial familiarity on repetition priming

Within the word recognition literature, word‐frequency and hence familiarity has been shown to affect the degree of repetition priming. The current paper reports two experiments which examine whether familiarity also affects the degree of repetition priming for faces. The results of Experiment 1 confirmed that familiarity did moderate the degree of priming in a face recognition task. Low familiarity faces were primed to a significantly greater degree than high familiarity faces in terms of accuracy, speed, and efficiency of processing. Experiment 2 replicated these results but additionally, demonstrated that familiarity moderates priming for name recognition as well as face recognition. These results can be accommodated within both a structural account of repetition priming ( Burton, Bruce & Johnston, 1990 ) and an Episodic Memory account of repetition priming (see Roediger, 1990 ), and are discussed in terms of a common mechanism for priming, learning and the representation of familiarity.     

Best face forward: Similarity effects in repetition priming of face recognition

Two experiments examined the graded similarity effect in the repetition priming of familiar face recognition. From the model of repetition priming proposed by Burton, Bruce, and Johnston (1990) it was predicted that similarity effects may be a confound of stimulus preparation. Experiment 1 was used to discount this hypothesis, but failed to replicate a pattern of graded priming related to the similarity of prime and target faces. Experiment 2 attempted a more extensive investigation using two different measures of prime-target similarity. The results replicated Ellis, Young, Flude, and Hay's (1987) finding that similar primes confer more priming than dissimilar ones, but found no correlation between amount of priming and the degree of prime-target resemblance for either similarity metric used. In view of these findings the mechanism of repetition priming in familiar face recognition is discussed.     

The locus of semantic priming effects in person recognition

Semantic priming in person recognition has been studied extensively. In a typical experiment, participants are asked to make a familiarity decision to target items that have been immediately preceded by related or unrelated primes. Facilitation is usually observed from related primes, and this priming is equivalent across stimulus domains (i.e., faces and names prime one another equally). Structural models of face recognition (e.g., IAC: Burton, Bruce, & Johnston, 1990) accommodate these effects by proposing a level of person identity nodes (PINs) at which recognition routes converge, and which allow access to a common pool of semantics. We present three experiments that examine semantic priming for different decisions. Priming for a semantic decision (e.g., British/American?) shows exactly the same pattern that is normally observed for a familiarity decision. The pattern is equivalent for name and face recognition. However, no semantic priming is observed when participants are asked to make a sex decision. These results constrain future models of face processing and are discussed with reference to current theories of semantic priming.     

Incomplete Faces Don't Show the Whole Picture: Repetition Priming from Jumbled Faces

Four experiments examined repetition priming of familiarity decisions to faces of famous people by the prior exposure of intact or jumbled faces. In Experiments 1 and 2 the primes were either the identical picture of the target face or a picture of the face with the internal features jumbled up. (In Experiment 2 the external features were also removed from all faces.) Compared with response times to previously unseen faces, familiarity decisions were made more rapidly if the subject had seen and identified the famous face in the pre-training stage; this was independent of whether they saw an intact or jumbled face. Priming was not shown if the face was not recognized earlier. Experiment 3 demonstrated that, if faces were not recognized spontaneously in the pre-training stage, being prompted as to their identity by the experimenter still did not yield priming at test-a result that replicated a previous study using incomplete faces (Brunas-Wagstaff, Young, & Ellis, 1992). Experiment 4 showed that it was the situation in which the information was given that was critical in determining whether priming occurred. The findings of this study are related to mechanisms for repetition priming of faces and used to discuss the necessity of modifications to the Bruce and Young (1986) model such as those offered by Burton, Bruce, and Johnston (1990).     

Neuropsychological Impairment of Face Recognition Units

Despite the absence of “conscious”, overt identification, some patients with face recognition impairments continue covertly to process information regarding face familiarity. The fact that by no means all patients show these covert effects has led to the suggestion that indirect recogntion tasks may help in identifying different types of face recognition impairment. The present report describes a number of experiments with the patient NR, who, after a closed head injury, has been severely impaired at recognizing familiar faces. Investigations mostly failed to show overt or covert face recognition, but NR performed at an above-chance level in selecting the familiar face on a task requiring a forced-choice between a familiar and an unfamiliar face. This discrepancy between a degree of rudimentary overt recognition and absence of covert effects on most indirect tests was addressed using a cross-domaim identity priming paradigm. This examined separately the possibility of preserved recognition for faces that NR consistently chose correctly in a forced-choice familiarity decision and those on which he performed at chance level. Priming effects were apparent only for the faces that were consistently chosen as “familiar” in forced-choice. We suggest that NR's stored representations of familiar faces are degraded, so that face recognition is possible only via a limited set of relatively preserved representations able to support a rudimentary form of overt recognition and to facilitate performance in matching and priming tasks.     

Face recognition and emotional valence: processing without awareness by neurologically intact participants does not simulate covert recognition in prosopagnosia

Covert face recognition in neurologically intact participants was investigated with the use of very brief stimulus presentation to prevent awareness of the stimulus. In Experiment 1, skin conductance response (SCR) to photographs of celebrity and unfamiliar faces was recorded; the faces were displayed for 220 msec and for 17 msec in a within-participants design. SCR to faces presented for 220 msec was larger and more likely to occur with familiar faces than with unfamiliar faces. Face familiarity did not affect the SCR to faces presented for 17 msec. SCR was larger for faces of good than for faces of evil celebrities presented for 17 msec, but valence did not affect SCR to faces displayed for 220 msec. In Experiment 2, associative priming was found in a face familiarity decision task when the prime face was displayed for 220 msec, but no facilitation occurred when primes were presented for 17 msec. In Experiment 3, participants were able to differentiate evil and good faces presented without awareness in a two-alternative forced-choice decision. The results provide no evidence of familiarity detection outside awareness in normal participants and suggest that, contrary to previous research, very brief presentation to neurologically intact participants is not a useful model for the types of covert recognition found in prosopagnosia. However, a response based on affective valence appears to be available from brief presentation.     

Multiple contributions to priming effects for familiar faces: analyses with backward masking and event-related potentials

The model of face recognition by Bruce and Young postulates a pool of structural representations for familiar faces in long-term memory, so-called face recognition units (FRUs). Event-related brain potentials show early repetition priming effects for familiar faces around 250-300 ms [N250r or early repetition effect (ERE)], which are thought to reflect the activation of these FRUs. However, small N250r effects are also seen for unfamiliar faces suggesting that priming of perceptual codes (i.e., pictorial and structural codes) also contributes to early repetition effects. Using a face-familiarity task in Experiment 1, we aimed to eliminate these perceptual contributions to face priming by backward masking the prime face with a different, unfamiliar face. As expected, a repetition priming effect appeared only for familiar faces. Experiment 2 used a semantic-decision task and compared the effects of different kinds of masks that interfered with either pictorial codes or with pictorial and structural codes. Our findings indicate that both structural codes and memory representations contribute to the N250r and that unfamiliar-face masks interfere only with structural codes. Face-masks may therefore provide a useful tool to extract the pure contributions of memory representations (i.e., FRUs) to repetition priming.     

Demonstrating how unfamiliar faces become familiar using a face matching task

Two experiments examine a novel method of assessing face familiarity that does not require explicit identification of presented faces. Earlier research (Clutterbuck & Johnston, 2002; Young, Hay, McWeeny, Flude, & Ellis, 1985) has shown that different views of the same face can be matched more quickly for familiar than for unfamiliar faces. This study examines whether exposure to previously novel faces allows the speed with which they can be matched to be increased, thus allowing a means of assessing how faces become familiar. In Experiment 1, participants viewed two sets of unfamiliar faces presented for either many, short intervals or for few, long intervals. At test, previously familiar (famous) faces were matched more quickly than novel faces or learned faces. In addition, learned faces seen on many, brief occasions were matched more quickly than the novel faces or faces seen on fewer, longer occasions. However, this was only observed when participants performed “different” decision matches. In Experiment 2, the similarity between face pairs was controlled more strictly. Once again, matches were performed on familiar faces more quickly than on unfamiliar or learned items. However, matches made to learned faces were significantly faster than those made to completely novel faces. This was now observed for both same and different match decisions. The use of this matching task as a means of tracking how unfamiliar faces become familiar is discussed.     

The speed of recognition of personally familiar faces

Despite the generally accepted notion that humans are very good and fast at recognising familiar individuals from their faces, the actual speed with which this fundamental brain function can be achieved remains largely unknown. Here, two groups of participants were required to respond by finger-lift when presented with either a photograph of a personally familiar face (classmate), or an unfamiliar one. This speeded manual go/no-go categorisation task revealed that personally familiar faces could be categorised as early as 380 ms after presentation, about 80 ms faster than unfamiliar faces. When response times were averaged across all 8 stimulus presentations, we found that minimum RTs for both familiar and unfamiliar face decisions were substantially lower (310 ms and 370 ms). Analyses confirmed that stimulus repetition enhanced the speed with which faces were categorised, irrespective of familiarity, and that repetition did not affect the observed benefit in RTS for familiar over unfamiliar faces. These data, representing the elapsed time from stimulus onset to motor output, put constraints on the time course of familiar face recognition in the human brain, which can be tracked more precisely by high temporal resolution electrophysiological measures.     

Holistic processing of shape cues in face identification: Evidence from face inversion,composite faces,and acquired prosopagnosia

According to a classical functional architecture of face processing (Bruce & Young, 1986), sex processing on faces is a parallel function to individual face recognition. One consequence of the model is thus that sex categorization on faces is not influenced by face familiarity. However, the behavioural and neuro-psychological evidences supporting this dissociation are yet equivocal. To test the independence between sex processing on faces and familiar face recognition, familiar (learned) faces were morphed with new faces, generating facial continua of visual similarity to familiar faces. First, a pilot experiment shown that subjects familiarized with one extreme of the face continuum roughly perceive one half of the continuum (60 to 100% of visual similarity to familiar faces) as made of familiar faces and the other part as unfamiliar. In the experiment proper, subjects were familiarized with faces and tested in a sex decision task made on faces at the different steps of the continua. Subjects were significantly quicker at telling the sex of faces perceived as familiar (60-100%), and the effect was not observed in a control (untrained) group. These results indicate that familiar face representations are activated before sex categorization is completed, and can facilitate this processing. The nature of the interaction between sex categorization on faces and familiar face recognition is discussed.     

Repetition priming of access to biographical information from faces

Two experiments examined repetition priming on tasks that require access to semantic (or biographical) information from faces. In the second stage of each experiment, participants made either a nationality or an occupation decision to faces of celebrities, and, in the first stage, they made either the same or a different decision to faces (in Experiment 1) or the same or a different decision to printed names (in Experiment 2). All combinations of priming and test tasks produced clear repetition effects, which occurred irrespective of whether the decisions made were positive or negative. Same-domain (face-to-face) repetition priming was larger than cross-domain (name-to-face) priming, and priming was larger when the two tasks were the same. It is discussed how these findings are more readily accommodated by the Burton, Bruce, and Johnston () model of face recognition than by episode-based accounts of repetition priming.     

Repetition priming of access to biographical information from faces

Two experiments examined repetition priming on tasks that require access to semantic (or biographical) information from faces. In the second stage of each experiment, participants made either a nationality or an occupation decision to faces of celebrities, and, in the first stage, they made either the same or a different decision to faces (in Experiment 1) or the same or a different decision to printed names (in Experiment 2). All combinations of priming and test tasks produced clear repetition effects, which occurred irrespective of whether the decisions made were positive or negative. Same-domain (face-to-face) repetition priming was larger than cross-domain (name-to-face) priming, and priming was larger when the two tasks were the same. It is discussed how these findings are more readily accommodated by the Burton, Bruce, and Johnston (1990) model of face recognition than by episode-based accounts of repetition priming.     

When sex isn't special: Priming onto a sex decision

Recognition of famous faces is speeded by prior exposure. This repetition priming has been shown for familiarity judgements (familiar/unfamiliar), semantic judgements (British/American), and naming. However, no benefit of priming has been found onto a sex judgement made to an image of a face. The absence of priming is normally explained by appealing to the fact that sex judgements can be made to a face without needing to access memory for that person, and that priming has its effects within the memory system. Here we ask subjects to make sex judgements to famous people's surnames (e.g., Tyson, Geldof), a task that requires them to access their memories for people. Under these conditions we observe the normal pattern of priming. We argue that structural, rather than episodic models of processing fit the data most naturally.     

Access to identity-specific semantic codes from familiar faces

Information codes that can specify the surface form of a face are contrasted with semantic codes describing the properties of the person to whom the face belongs. Identity-specific semantic codes that specify characteristics of familiar people based on personal knowledge are in turn contrasted with the visually derived semantic codes and expression codes that can be derived even from unfamiliar faces. The idea that familiarity decisions (i.e., categorizing faces as belonging to known or unknown people) can be based on surface form, whereas certain types of semantic decision demand additional access to identity-specific semantic codes was investigated in four experiments. Experiments 1 and 3 showed that decisions based on identity-specific semantic codes (semantic decisions) usually take longer than decisions that do not demand access to an identity-specific semantic code (familiarity decisions). Experiment 2 showed that the use of familiar faces drawn from consistent or mixed categories affected reaction times for semantic decisions but not for familiarity decisions. Experiment 4 showed that semantic decisions to faces are taken more quickly (primed) when the faces have been recently seen, whereas there is no differential effect on semantic decisions to faces from previous semantic decisions involving the same people's names. These findings are consistent with the view that identity-specific semantic codes are accessed via face recognition units, and that outputs from face recognition units (which respond to the face's surface form) can be used as the basis for familiarity decisions.