Which statistical test for small sample repeated measures research

I have interval data for 8 participants' responses to 11 sequential stimuli and trying to identify any pattern in increasing/decreasing response. Attempted to run a one-way repeated measured ANOVA through SPSS but got no sphericity value - have been told this might be because I have fewer participants than levels. If this is the case what other options do I have to analyse my data. I am relatively new to stats so please explain your answers -- thank you!!