Table 1.

Characteristics of the selected studies.

Study	Sample	Selection criteria	N experimental group	N control group
Ang et al. [2]	School-age children	Low working memory	32 (updating), 25 (Cogmed)	28
Bergman Nutley et al. [3]	Preschool children	none	24	26
Bigorra et al. [4]	School-age children	ADHD	30	31
Brehmer et al. [5]	Adults	20–30 years & 60–70 years	54	45
Chacko et al. [6]	School-age children	ADHD	44	41
Chooi & Thompson [7]	Adults	None	15	26
Dentz et al. [8]	18–63 years	ADHD	23	21
Dunning & Holmes [9]	18–21 years	None	15	15
Foster et al. [10]	18–35 years	Low and high memory span	40 (complex span), 39( running span)	39
Gray et al. [11]	Adolescents	Learning difficulties & ADHD	32	20
Harrison et al. [12]	Adults	None	21 (complex span), 17 (simple span)	17
Henry et al. [13]	School-age children	None	18	18
Hitchcock, Westwell [14]	School-age children	None	50	44
Karbach et al. [15]	School-age children	None	14	14
Kundu et al. [16]	Adults	None	15	15
Lawlor-Savage, Goghari [17]	Adults	None	27	30
Metzler-Baddeley et al [18]	Adults	None	20	20
Minear et al. [19]	Adults	None	31 (n-back1), 32 ( complex span)	26
Passolunghi & Costa [20]	Preschool children	None	15	15
Redick et al. [21]	Adults	None	24	29
Thompson et al. [22]	Adults	None	20	19
Van der Molen et al. [23]	Adolescents	Learning difficulties	41	26
von Bastian et al. [24]	Adults	18–35 years & 61–77 years	61	62