Intact word processing in developmental prosopagnosia

Abstract

A wealth of evidence from behavioural, neuropsychological and neuroimaging research supports the view that face recognition is reliant upon a domain-specific network that does not process words. In contrast, the recent many-to-many model of visual recognition posits that brain areas involved in word and face recognition are functionally integrated. Developmental prosopagnosia (DP) is characterised by severe deficits in the recognition of faces, which the many-to-many model predicts should negatively affect word recognition. Alternatively, domain-specific accounts suggest that impairments in face and word processing need not go hand in hand. To test these possibilities, we ran a battery of 7 tasks examining word processing in a group of DP cases and controls. One of our prosopagnosia cases exhibited a severe reading impairment with delayed response times during reading aloud tasks, but not lexical decision tasks. Overall, however, we found no evidence of global word processing deficits in DP, consistent with a dissociation account for face and word processing.

Figure 1

Neuropsychological testing results of the 11 DP cases that participated in the experiments. Columns indicate: Famous Faces Test (FFT), Cambridge Face Memory Test (CFMT), Cambridge Face Perception Test upright and inverted (CFPTupr and CFPTinv).

Figure 2

Results for Lexical Decision: Length (word confusability not controlled). Data for words and non-words (NW) are shown in left panel (response time) and right panel (number of errors) for control and DP groups. Error bars indicate ±SEM. The three word conditions are words comprised of 3-, 5-, or 7-letters. As there were 3 times more items in the NW condition, the NW errors were divided by 3 to make their rates displayed in the graph proportionally comparable to the word conditions.

Figure 3

Results for Reading Aloud: Length (word confusability not controlled). Data are shown in left panel (response time) and right panel (number of errors) for control and DP groups. Error bars display ±SEM. The three conditions are words comprised of 3-, 5-, and 7-letters.

Figure 4

Results for Reading Aloud: Length (sum confusability maintained across words). Data are shown in left panel (response time) and right panel (number of errors) for control and DP groups. Error bars show ±SEM. The three conditions are words comprised of 5-, 6-, or 7-letters with sum confusability controlled for across all words.

Figure 5

Results for Reading Aloud: Length (average letter confusability maintained across words). Data are shown in left panel (response time) and right panel (number of errors) for control and DP groups. Error bars show ±SEM. The three conditions are words comprised of 5-, 6-, or 7-letters with average confusability controlled for across all words.

Figure 6

Results for Lexical Decision: Frequency x AoA. Data for words and non-words (NW) are shown in left panel (response time) and right panel (number of errors) for control and DP groups. Error bars indicate ±SEM. The four word conditions are high frequency/early acquisition (H/E), high frequency/late acquisition (H/L), low frequency/early acquisition (L/E), and low frequency/late acquisition (L/L). As there were 4 times more items in the NW condition, the NW errors were divided by 4 to make their rates displayed in the graph proportionally comparable to the word conditions.

Figure 7

Results for Reading Aloud: Frequency x AoA. Data are shown in left panel (response time) and right panel (number of errors) for control and DP groups. Error bars indicate± SEM. The four conditions are words of high frequency/early acquisition (H/E), high frequency/late acquisition (H/L), low frequency/early acquisition (L/E), and low frequency/late acquisition (L/L).

Figure 8

Results for Reading Aloud: N Confusability. Data are shown in left panel (response time) and right panel (number of errors) for control and DP groups. Error bars indicate ±SEM. The four conditions are words of high n/high confusability (HN/HC), high n/low confusability (HN/LC), low n/high confusability (LN/HC), and low n/low confusability (LN/LC).

Figure 9

T-values of individual DP cases that were impaired on a single condition. The columns on the left show response time performance with the columns on the right showing the error rates. L1-L4 relates to the four length tasks in order as presented in our Results section. AxF LDT = Age of Acquisition × Frequency Lexical Decision task, AxF Name = Age of Acquisition × Frequency Naming task, N/Con = N × Confusability task. Asterisks highlight lexical decision tasks and Xs denote tasks that were not completed by the participant.