The face-inversion effect (FIE) refers to the observation that inversion impairs the processing of faces disproportionally more than other mono-oriented objects. The FIE has further been found to be abolished or reduced in acquired prosopagnosia. Whether this is also true of developmental prosopagnosia (DP) is less clear with reports of normal FIEs, reduced/abolished FIEs or even paradoxical FIEs (better performance with inverted than upright faces). We compared FIEs in 17 DPs and 17 matched controls by contrasting performance on the Cambridge Face and Car Memory Tests with upright and inverted stimuli. The DP-group showed a reliable inversion effect for faces which was nevertheless significantly reduced compared with that seen in the control-group. In comparison, there was no reliable group difference for cars. The FIE was reliable in the control- but not the DP-group and it was reliably larger in the control- than in the DP-group (interaction effect), suggesting an abolishment of the FIE in the DP-group. On a single-case level 3 DPs showed a (classical) dissociation with the difference between upright and inverted faces being smaller than that observed in the control-group. In all three cases performance was better, although not reliably better, with inverted faces. Two other DPs showed a (classical) dissociation with the difference between upright and inverted cars being larger than that observed in the control-group. In both cases, performance was significantly better with upright cars. Finally, of the three DPs exhibiting a reduced inversion effect for faces, only one showed a (classical) dissociation with regards to the FIE, with the difference between upright and inverted faces on the one hand and the difference between upright and inverted cars on the other deviating significantly from the control-group. The finding of reduced/abolished but no paradoxical FIEs in DP mirrors findings in acquired prosopagnosia.

Meeting abstract presented at VSS 2017