Task (Code enclosed) Participants fixate a small red cross in the center of the screen for the whole trial. Around the cross black letters (X, Y, Z) are located in 7 rows with 17 letters each. For each position the type of letter is randomly drawn. Around this central square of letters 8 black #-symbols are located equally-spaced on an imaginary circle with a radius of 200 pixels. This waiting screen is shown for 1000 ms. Afterwards, at the location of one of the eight #-symbol, a number appears (1,2,3,4 or 6,7,8,9) for 300 ms. This is the target. Participants are asked to react as quickly as possible and press a pre-defined key if the number is smaller than 5 and another key if the number is greater than 5. In 80 out of 160 trials the target number appears alone at the location of the #-symbol while the other positions are blank. This is the low-load condition. In the remaining 80 trials (high load) the target number appears as well at one out of the eight #-symbol positions while the other positions are filled with the letters J, Z, E, A, G, B, P and R. Simultaneously, the letters around the fixation cross change again. In all 160 trials, unexpectedly, half of the letters are not randomly replaced by another letter but by a number (1,2,3,4 or 6,7,8,9). In 50% of these trials the unexpected number matches the category of the target number, but is not the same – a congruent trial. In 50% of the trials the unexpected number mismatches the category of the target number – an incongruent trial. Participants are asked to respond as quickly as possible and decide whether the target number is smaller or greater than 5. They have a maximum time interval of 2000 ms to respond. After the 300 ms presentation of the target screen, a blank screen is shown. If a response was made, the next trial starts immediately. Every 27 trials participants receive feedback (% correct, mean reaction time) and can take a break for as long as they want. Practice trials: Each participant solves 20 practice trials (all without unexpected stimuli) before the 160 experimental trials . At the end of the practice block participants receive feedback about the number of correct responses and the average reaction time. Participants have to repeat the practice block if they do not at least have 17 correct responses. Questions concerning the unexpected numbers: After completion of the main part of the task, participants are asked if they noticed anything around the central fixation cross other than the three letters X, Y, and Z. If they respond "yes" they are further asked to describe in detail what they noticed and how many times. Full-attention trials: Participants complete a block of 20 more trials on the computer. They are instructed to not attend to the circle of #-symbols and the target number any more. In each trial, half of the positions around fixation are filled with one of the numbers from before. After each trial participants are asked which number they have seen. Visual acuity test: After completion of the full-attention trials participants were tested for their visual acuity to ensure normal or corrected-to-normal sight. For that reason participants complete a block of 10 trials on the computer. In every trial they are presented with a number (same font and size as the unexpected numbers before) and have to type the number with the keyboard. At the end participants were asked about anticipation of an unexpected stimuli and general knowledge about IB. They also give demographic variables.