Table 2.

Global and local switch costs in terms of mean RTs for correct responses (in ms) for each participant group and for each discrimination task.

Groups	Global SC			Local SC			ANOVA				Contrast Tests
	M	SE	99% CI	M	SE	99% CI	Effect	F ratio	df	Partial ƞ2	GC	Global SC	Local SC
Letter Discrimination Task
College Students	71	26	[2,140]	215	21	[159,270]	G	719.38**	1	0.87	1	t(50.2) = −5.4**	t(54.6) = −6.1**
61–74 year olds	249	31	[168,330]	429	25	[364,494]	T	24.18**	1	0.18	2	t(22.6) = −2.1*	t(29.7) = −5.1**
75–89 year olds	220	40	[114,326]	405	33	[320,491]	C	19.47**	1	0.15	3	t(29.6) = 0.4	t(50.7) = 0.5
Brightness Discrimination Task
College Students	105	14	[67,142]	93	14	[58,129]	G × T	6.88**	2	0.11	1	t(49.6) = −6.7**	t(52.9) = −6.0**
61–74 year olds	260	17	[216,304]	201	16	[160,242]	G × C	0.08	2	0.00	2	t(26.2) = −7.9**	t(23.2) = −5.7**
75–89 year olds	320	22	[262,377]	289	21	[234,343]	C × T	77.02**	1	0.41	3	t(47.8) = −1.8	t(31.3) = −2.4*
							G × C × T	1.53	2	0.03

Note. SC = Switch Costs; Global SC = performance difference between pure and no-switch trials. Local SC = performance difference between no-switch and switch trials; ANOVA = analysis of variance; G = group; T = task type; C = switch cost type; CI = confidence interval; GC = group comparisons (1 = college students vs. 61–74 year olds; 2 = college students vs. 75–89 year olds; 3 = 61–74 year olds vs. 75–89 year olds).

^*p < .05;

^**p < .01.