Recognizing and identifying people: A neuropsychological review

Abstract

Recognizing people is a classic example of a cognitive function that involves multiple processing stages and parallel routes of information. Neuropsychological data have provided important evidence for models of this process, particularly from case reports; however, the quality and extent of the data varies widely between studies. In this review we first discuss the requirements and logical basis of the types of neuropsychological evidence to support conclusions about the modules in this process. We then survey the adequacy of the current body of reports to address two key issues. First is the question of which cognitive operation generates a sense of familiarity: the current debate revolves around whether familiarity arises in modality-specific recognition units or later amodal processes. Key evidence on this point comes from the search for dissociations between familiarity for faces, voices and names. The second question is whether lesions can differentially affect the abilities to link diverse sources of person information (e.g., face, voice, name, biographic data). Dissociations of these linkages may favor a 'distributed-only' model of the organization of semantic knowledge, whereas a 'person-hub' model would predict uniform impairments of all linkages. While we conclude that there is reasonable evidence for dissociations in name, voice and face familiarity in regards to the first question, the evidence for or against dissociated linkages between information stores in regards to the second question is tenuous at best. We identify deficiencies in the current literature that should motivate and inform the design of future studies.

Keywords: Face; Familiarity; Hub; Name; Semantic; Voice.

Figure 1

Cognitive stage models of person identification. In Bruce and Young (1986), perceptual face encoding is followed by matching to a representation of previously seen face in the face recognition unit (FRU), which leads to access to semantic information in a person identity node (PIN) and generation of the name. In Burton and Bruce (1992) the PIN is an amodal hub mediating access to semantic stores, of which the name is part, while in Brédart et al (1995) names are a separate information store. Ellis et al (1997) and Belin et al (2004) added a parallel route for identification from voices. Gainotti (2013) proposed hemispheric differences, with face and voice processing lateralized to the right and names to the left, as well as separate semantic stores for sensory and verbal information. NRU = name recognition unit, VRU = voice recognition unit.

Figure 2

Models of linkages between sensory and semantic information. In the person-hub model, linkages are mandatorily mediated by the PIN (person identity node) and are conceptualized as spokes emanating to and from this hub. In the distributed-only model the PIN is a store of verbal semantic knowledge and not a hub, and bi-directional linkages pass directly between the sensory information residing in different recognition units as well as the PIN.

Figure 3

Logical inference in a 2-stage cognitive model. Green indicates intact function, red indicates impaired function, and orange partial function. i) Impaired output (out) can only imply damage in module B if module A is intact as shown by normal intermediate output a. ii) Conversely, impaired output (out) does not allow any conclusion about the integrity of module B, which is therefore shaded an ambiguous grey, if module A is dysfunctional, as shown by impaired intermediate output a, unless one can provide an alternative input x to module B that bypasses module A. iii) inability to link the information of modules B and D can only be considered as evidence of disrupted linkage z if modules B and D are known to be intact. iv) If the output (out) from module B is normal, then one can infer that module A is also intact, even if its intermediate output a is not assessed. v) In an interactive model with feedback as well as feedforward connections, if module B is impaired, intact module A may have a degraded intermediate output a if it uses not only feedforward input (in) but also feedback information from module B.

Figure 4

Excluded cases. Green indicates reported normal function, red indicates impaired function, and orange borderline function. Light green indicates normal results and pink indicates abnormal results on tests that may not be adequate to evaluate the intermediate output of a module. The grey zone in the top bar indicates the lesion side, with distinct grey and white halves indicating unilateral lesions, and graded shading indicating asymmetric lesions that may not be strictly unilateral. For patients of Neuner and Schweinberger (2000), the stippling on the less affected side indicates uncertainty about whether the lesion is strictly unilateral, as information about the pathology in each subject was not given. Top two rows show cases in which demonstrated impairments in perceptual encoding invalidate observations of dissociations at the recognition units or later. Bottom two rows show cases in which proof of intact perceptual encoding preceding a reportedly dysfunctional recognition unit is lacking or inadequate.

Figure 5

Cases with impaired familiarity for voice, face or name. Pictorial conventions as in Figure 4. Top row and case 24 in second row are cases with left-dominant lesions, the following show cases with right-dominant lesions, and the last three cases have bilateral lesions without clear dominance.

Figure 6

Cases with impaired linkages. Pictorial conventions as in Figure 4. Top row shows cases of limited value, because assessments of familiarity are either lacking or indicate impairment at the level of recognition units. Middle row shows potentially informative cases with right-dominant lesions, bottom row those with left-dominant lesions.

Figure 7

Group studies, left hemisphere lesions. Pictorial conventions as in Figure 4. The grey zone depicting lesion type for each group also includes reported sample sizes in parentheses.

Figure 8

Group studies, right hemisphere lesions. Pictorial conventions as in Figure 8. The grey zone depicting lesion type for each group also includes reported sample sizes in parentheses.