3.2. Results and discussion There were no detectable effects of day of testing on any of the behaviours. On the
other hand, there were significant effects of rearing on the chicks’ latencies to enter zone Ž
. 4 as well as on their approach scores, numbers of steps and of areas entered Table 1 . In
general terms, SS chicks entered zone 4 sooner, spent longer in that area and were more active than the controls. However, there were significant interactions between rearing
and test conditions on two of the variables; SSrSS chicks entered zone 4 sooner and scored higher approach than SSrBC ones whereas the reverse was true for NrSS and
NrBC chicks. These findings probably reflect attraction towards the video image in the open field by SS chicks because of its familiarity whereas the novelty of this stimulus
likely elicited neophobia and avoidance in the naive controls.
Analysis of variance also revealed a significant effect of test condition on the latency to vocalize; the presence of SS in the open field delayed vocalization regardless of
Ž .
rearing condition Table 1 . This effect in the N controls, which had never experienced the video, probably reflected their fear of this novel stimulus whereas the presence of
this familiar stimulus may have dampened the expression of this social reinstatement Ž
. behaviour Faure et al., 1983 in SS ones.
Fear inhibits all other behaviour systems, including exploration and social reinstate- Ž
. ment see Jones, 1996 . Therefore, our findings that SS chicks were significantly more
active in the open field and tended to vocalize sooner and more than N ones, regardless of test condition, suggested that prior video stimulation may have reduced underlying
fearfulness. This suggestion was examined in Experiment 2.
4. Experiment 2
4.1. Treatments and testing Forty-eight 1-day-old female ISA Brown chicks were housed in groups of six and
assigned at random to one of two treatments. Half the chicks were exposed to a Ž
. Ž
. composite video CV of 5 Apple Macintosh SS programmes see below for 20 min,
twice a day, from 2 to 8 days of age. The video was filmed from a computer monitor using a camcorder. It lasted 20 min and consisted of 4 min each of ‘String Theory’
Žseveral bundles of lines change colour as they curve and sweep across a black
. Ž
. Ž
background , ‘Fish’ as in Experiment 1 , ‘Satori’ a complex coloured pattern, moving .
Ž in swirls and ripples , ‘Flying Toasters’ symbols of small winged toasters and pieces of
. Ž
toast move diagonally across the screen from right to left and ‘Doodles’ a number of coloured wavy lines appear on the screen at random; the screen is refreshed after a few
. seconds and a different number of lines appears , respectively. All the screensavers were
Ž .
thought to be biologically neutral see Experiment 1 . The video monitor was presented to the chicks as described in Experiment 1.
At 9 or 10 days of age, the birds were tested individually in the same open field that was used in Experiment 1, although this time the window was covered with black card
so that all the walls were uniformly black. No video images were presented at test on
Table 2 Ž
. Open-field responses back-transformed meansstandard errors of chicks that had either received regular
Ž .
Ž .
exposure to a composite video CV of five screensavers or not controls, C Behaviour
Treatment P
Ž .
Ž .
CV ns 24 C ns 24
df s1 Ž .
Duration of freezing s 2.70.8
8.12.6 -
0.05 Ž .
Lat. to vocalize s 5.71.4
13.53.3 s 0.06
Ž . Lat. to step s
55.711.9 53.311.5
NS Ž
. Vocalizations no.
895.044.6 882.744.0
NS Ž
. Areas entered no.
58.94.7 34.92.8
- 0.01
Ž . Ž
. df s Degrees of freedom; Lat.s latency to; s sseconds; no. s number; NSs not significant, P 0.05.
this occasion. Vocalization and freezing were recorded directly and a videotape record was made of the chicks’ other behaviours. Upon reviewing the videotapes we measured
the latency to the first step and the numbers of areas entered during the 10-min test period.
Ž .
Ž . The numbers of experimental composite video, CV and control C chicks that
exhibited freezing were compared using a x
2
test. The remaining data were not normally distributed and were therefore transformed to logarithms. An analysis of
variance was then used to examine the effects of treatment, day of testing and their interactions.
4.2. Results and discussion Ž
Fewer CV than C chicks exhibited freezing behaviour 8 vs. 17, respectively,
2
. x s 8.35, df s 1, P - 0.01 .
The analysis of variance revealed no detectable effects of day of testing and no significant interactions. However, treatment effects were apparent. The CV chicks
showed significantly shorter durations of freezing and they entered significantly more Ž
. areas of the open field than did C ones Table 2 . A numerical tendency for CV birds to
vocalize sooner than C chicks only narrowly failed to reach significance. The present results provide further evidence that regular exposure to a complex video image during
the first week of life reduced chicks’ later fear of a strange environment.
5. General discussion
