Table 2.

Results of the exploratory factor analysis

Observed variables	Factor loadings
	F1	F2
SAS score	0.85	0.27
DAS-Executive score	0.66	0.11
Mean(FP+GP) Activity time ratio	− 0.48	0.21
Mean(FP+GP) Walking acceleration	− 0.36	0.02
Mean(FP+GP) Walking duration	0.34	0.12
Mean(FP+GP) Walking occurrences	0.33	− 0.05
DAS-Initiation score	0.21	0.67
Delta(FP-GP) Walking duration	− 0.12	0.63
DAS-Emotional score	0.14	0.60
Delta(FP-GP) Walking acceleration	0.12	− 0.53

Values indicate the factor loadings of the EFA. Coefficients in bold represent the highest loading (among the two factors) for each item. The calculation of individual scores on F1 and F2 takes into account all the factor loadings onto F1 and F2, respectively. N = 36 (bvFTD: N = 20/controls: N = 16)

Mean_(FP+GP), mean calculated on the total of free and guided phases ((FP + GP)/2); Delta_(FP-GP), delta calculated as the difference between free and guided phase (FP-GP); activity time ratio, ratio of time spent in goal-directed behaviors; walking occurrences, occurrences of walking episodes; walking acceleration, mean acceleration of walking episodes; walking duration, mean duration of walking episodes; SAS, apathy defined as a global lack of motivation (assessed as a unidimensional construct); DAS-Emotional, diminished integration, processing and expression of emotions; DAS-Initiation, lessened initiation of thoughts and actions; DAS-Executive, inability to manage goals and cognitively strategize to execute a plan of actions