The function takes a string as input and shifts each character by a certain number of positions in the alphabet.

[CODE]:
```python
def shift_string(input_string):
    output_string = ""
    shift_amount = 1  # replace with the actual shift amount observed in the experiments

    for char in input_string:
        # Assuming char is a lowercase letter
        shifted_char = chr((ord(char) - ord('a') + shift_amount) % 26 + ord('a'))
        output_string += shifted_char

    return output_string
```

Please note that the shift_amount value needs to be determined by running additional experiments on different input strings and analyzing the corresponding outputs.