There were three losing trial types designated as one-of-a-kind, two-of-a-kind, and three-of-a-kind, and one winning trial type designated as four-of-a-kind.
In the present study, the same stimuli were used on both winning and losing trials.
On all losing trials the bird was still required to respond to the tumblers to advance to the next trial.
Outlier trials consisted again of less than 2% of the remaining data, and lost trials due to Wiimote pairing less than 4%.
Losing trials, therefore, could only be identified by recognising that the first nonidentical stimulus following one, two, or three identical stimuli signalled reward omission.
For descriptive purposes, we additionally conducted first-order parametrical analyses of anticipation phases of losing trials (LA1) and outcome phases of lost losing trials (LOL1) [Additional file 1].
There were two types of trials (2nd factor), winning trials and losing trials, with two possible outcomes, respectively (3rd factor): In winning trials participants either won or did not win a chocolate bar; in losing trials, already won chocolate bars were either lost or not lost.
This was applied to the anticipation phases of winning trials and losing trials, the outcome phases of winning trials that were won and not won, and the outcome phases of losing trials that were not lost and lost (contrasts are indicated by ** 1, e.g., WA1).
We also included losing trials into our experiment to balance the amount of gained rewards and to dissociate gain from loss phases (see methods section).
In the announcement phase the brand logo was presented in the middle of a wheel of fortune with six colored (green for wining trials, red for losing trials) and six black fields.
However, as winning trials were explicitly separated from losing trials, the pattern of activation is unlikely to reflect engagement in anticipating losses or punishment rather than receiving rewarding stimuli.
