All inspection trials were videotaped from a camera suspended above the
inspection tank. The position of the inspector relative to the predator was
recorded to the nearest centimeter (from 0 to 40, with 40 being closest possible to
the predator) every 5 s for the duration of the trial. For each inspector, a mean
distance from the predator was calculated to determine which fish maintained a
closer average position to the predator. These data were transcribed from the
videotape and calculated using marks on the rim of the aquarium which were
invisible to the fish themselves.
Immediately following the inspection session, all three fish were netted and
placed back in the original preference test aquarium. After a 5 min acclimatization period, the observer was given a second preference test, with the position of
the inspectors switched compared with the initial preference test to determine if
the observer’s preference had changed. Thirty series consisting of an initial
preference test, an inspection trial, and a post-inspection preference test were
conducted for each of the three treatments (see below).