In a sample of four prosopagnosics Tree and Wilkie (2010) found an imagery deficit for faces, while the self-report questionnaires they used did not show any reduction in the vividness of visual mental imagery (VVMI). They did not find any reduction of mental imagery for objects or colors in their subjects. The authors tested the imagery with a set of questions about external and internal facial features of celebrities and about features of objects. In our recent study (Gruter et al., 2009), explicitly referred to by Tree and Wilkie (2010), we evaluated the self-rated imagery of 53 congenital prosopagnosicsand found that thevividnessof theirmental imagery was quite low e in fact the prosopagnosic group showed the lowest average mental imagery scores ever published for a non-brain-damaged group. This reduction of imagery capabilities was more pronounced for faces than for objects. The difference between Tree and Wilkie’s results and ours may have several reasons: First, they examined a smaller sample thanwe did (4 prosopagnosics against 53 in our study). Second, the different diagnostic procedures may play a role. Third, the different interpretation of visual mental imagery assessment methodology has to be considered. A fourth reason may be their selection of controls. Our diagnostic criteria for congenital prosopagnosia (cPA) differ from theirs. First of all, prosopagnosia is a symptom, not a condition or a disease per se. Like in the case of headaches, the complaints need to be specified before any useful additional studies can be done. Tree and Wilkie (2010) label all cases unequivocally as “congenital prosopagnosics” by referring to Jones and Tranel’s (2001) criteria, although Jones and Tranel investigated a 5-year-old boy with developmental prosopagnosiada type of prosopagnosia that is not necessarily congenital. Our studies have indicated that people with cPA typically show a distinct pattern of complaints (Table 1). The leading symptom in cPA is an irritating inability to decide whether a face is familiar or not (Gruter et al., 2009, 2007, 2008). This discerns the condition from acquired prosopagnosia, where most of the affected people report that all faces look definitely unfamiliar to them. Aiming at an enhancement of the specification of complaintswe also ask for face-related cognitive impairments not normally associated with cPA. These include the recognition of facial emotions (Humphreys et al., 2007), recognition of facial attractiveness (Carbon et al., 2010), recognition of gender from faces (Gruter et al., 2008), color vision (often impaired in acquired prosopagnosia), field of vision (often reduced in acquired prosopagnosia) (Bouvier and Engel, 2006), semantic memory for persons, and person recognition from non-facial clues (Gruter et al., 2008). If the interviewee reports problems with these cognitive functions, he/she may suffer from a different condition, in which prosopagnosia (PA) is just one symptom (see Gruter et al., 2008, for a more detailed discussion on the differential diagnosis). Our behavioral diagnostic procedure uses a semi-structured interview form conducted by an experienced physician or psychologist. The interviewee does not fill out any form, all forms (see supplementary online material) must be filled out by the interviewer. The interview should also cover the completemedical and neurological history in order to exclude any condition that may mimic a prosopagnosia like for