def find_image_dprimes(df_clean):
    df_hits = 1-df_clean.query('stim_trial == "stimulation" and side == "left"').groupby(['active_LED','image_number']).mean()['looked_up']
    df_hits = df_hits.replace(to_replace=1, value=.99)

    df_fa = 1-df_clean.query('stim_trial == "no stimulation" and side == "left"').groupby(['active_LED','image_number']).mean()['looked_up']
    df_fa = df_fa.replace(to_replace=0, value=.01)
    dprime = df_hits.apply(norm.ppf)-df_fa.apply(norm.ppf)
    return(dprime)