1 Introduction Berlyne, 1950, 1960; Glickman and Sroges, 1966; Welker, 1957 Montgomery, 1954, 1955; Montgomery and Monkman, 1955 Greenberg, 2003 Greenberg, 2003 Hughes, 2007 Bardo et al., 1996 Hall, 1934, 1936 Crawley, 1985; Whishaw et al., 2006 Birke and Sadler, 1986; Denenberg, 1969; Renner, 1990; Walsh and Cummins, 1976 Marin et al., 2007; Matzel et al., 2006; Rees et al., 2006 Prut and Belzung, 2003 Prut and Belzung, 2003 Berlyne, 1960; Birke and Archer, 1983 hole-board File and Wardill, 1975a,b; Nolan and Parkes, 1973 File and Wardill, 1975a; Ljungberg and Ungerstedt, 1976 Abel, 1995; Durcan and Lister, 1989; File, 1977; Lister, 1987; Rogers et al., 1999 Crawley, 1985; Takeda et al., 1998 Kliethermes and Crabbe, 2006a File, 1977 Nolan and Parkes, 1973; Takeda et al., 1998 Pellow et al., 1985 Sayin et al., 1992 Kliethermes and Crabbe, 2006a Kliethermes and Crabbe, 2006b Bilkei-Gorzó and Gyertyán, 1996; Renner, 1990 Leussis and Bolivar, 2006 Nolan and Parkes (1973) Gagliano et al., 2008; Mayeux-Portas et al., 2000 File and Wardill, 1975a Aguilar et al., 2003; Ray and Hansen, 2004 2 Materials and methods 2.1 Subjects and housing ad libitum 2.2 Apparatus and experimental design The hole-board apparatus consisted of a wooden, grey box, measuring 68 cm × 68 cm. The walls were 40 cm high, and the box was raised 28 cm above the ground on a metal stand. Four holes (4 cm in diameter) were cut into the floor of the apparatus; each hole was 28 cm from a corner of the box along the diagonal from the corner to the centre. The floor of the box was marked out into four outer areas and one central area using black masking tape. The central area was delineated by four lines of tape each 20 cm from one of the walls, while the four outer areas were marked out by diagonal lines of tape running from the corners of the floor to the corners of the central square. The four holes were thus located at the corners of the central square. The apparatus was located in a small testing room with dimmed white lighting. The stand of the apparatus was open on all sides, allowing the floor or objects to be dimly lit. Each subject was tested ten times in the hole-board apparatus, once per day during two sets of five consecutive days (Monday–Friday and the following Monday–Friday). During the first set of five trials, no objects were present underneath the holes of the apparatus; during the second set of five trials, an object was placed on the floor under each of the four holes prior to the start of the trial, approximately 20 cm below each hole. The objects were all distinct from each other but were similar in size (approximately 10 cm in length or diameter: a black-and-white rubber ball, a purple plastic star, a red-and-white rubber pet toy, and a yellow, rubber dumb-bell shaped pet toy). All trials were carried out between 09:00 and 17:00 h, and trials on males and females were alternated throughout the day. At the beginning of each trial, a subject was placed in one corner of the apparatus (always the corner closest to the door of the room), facing the centre of the arena. Each trial lasted 10 min. At the end of the trial, the subject was immediately placed into a carrying box and returned to the home cage. Between each trial, the floor and walls of the apparatus and the novel objects, if present, were cleaned with 70% alcohol solution. 2.3 Behavioural measurements (i) enter a new area: the animal moves from one area of the open field to another (all four paws had to be placed on the floor of a new area); (ii) head-dip: the animal places it's head into one of the holes, to a minimum depth such that the ears were level with the floor of the apparatus (a new bout of head-dipping was recorded if the animal raised it's head fully out of the hole before resuming); (iii) rear: the animal is stationary on it's backpaws and raises it's forepaws off the ground, extending it's body vertically. The data on entries into a new area were used to calculate the total amount of locomotion (number of entries into all areas summed together) and the percentage of entries that were in made into the central area. The location of the animal during each of the 10-s time intervals was used to estimate the percentage of time spent in the central area. 2.4 Statistical analyses post hoc Howell, 2007 3 Results 3.1 Total locomotion F 4,56 F 4,56 F 1,14 p Table 1 F 4,56 F 4,56 F 4,56 F 4,56 3.2 Locomotion into the central area F 4,56 p F 1,56 p F 4,56 p Post hoc Fig. 1 F 1,14 p Table 1 F 4,56 F 4,56 F 4,56 3.3 Time spent in the central area F 4,56 p F 1,56 p F 4,56 p Fig. 1 F 1,14 p Table 1 F 4,56 F 4,56 F 4,56 3.4 Frequency of head-dipping F 4,56 p F 4,56 p Fig. 2 F 1,14 F 1,14 p Table 1 F 4,56 F 4,56 F 4,56 3.5 Frequency of rearing F 4,56 p Fig. 3 F 1,14 F 1,14 Table 1 F 4,56 F 4,56 F 4,56 F 4,56 4 Discussion The aim of this study was to investigate whether head-dipping behaviour should be considered a valid measure of neophilia by comparing performance on the hole-board task (a) over repeated sessions (trials 1–10) and (b) when no objects were present (trials 1–5) and when objects were placed underneath the holes (trials 6–10). The results show that head-dipping was high during the first test, decreased over the following two trials and remained relatively stable during the rest of the experiment. The initial drop in head-dipping following the first trial could be interpreted in two ways. First, head-dipping could be indicative of a neophilic response that decreases as the animal becomes familiar with the apparatus, i.e. head-dipping represents directed exploratory behaviour that drops as the apparatus loses its novelty. If this interpretation is correct, we would also predict that head-dipping would be greater in the presence of objects; however, there was no evidence of an increase in head-dipping behaviour when objects were present underneath the holes. These results do not support the hypothesis that head-dipping is a valid measure of neophilia. Renner, 1990 Márquez et al., 2005, 2006 Belzung and Griebel, 2001 Gagliano et al., 2008; Mayeux-Portas et al., 2000; Nolan and Parkes, 1973 Nolan and Parkes (1973) Nolan and Parkes, 1973 Lever et al., 2006 Bilkei-Gorzó and Gyertyán (1996) Cook et al., 2002; Dawson et al., 1994; Rodgers et al., 1996 Aguilar et al., 2003; Ray and Hansen, 2004 Garey et al., 2001; Morgan and Pfaff, 2002 Morgan et al., 2004 Cortright et al., 1997; Eckel and Moore, 2004 Welker, 1957 Greenberg, 2003