rat was left at its normal temperature. In his second experiment, which looked at hedonic and aversive reactions to taste, Zajonc connected the hypothalamic thermode of the 17 rats to water flow, and the rat's were connected to an infusion delivery tube. Rats were infused with pure sucrose, a sucrose/quinine mixture, or distilled water, in random order through a 1-minute period, once per day. The thermode was then either cooled or heated by 2.5 °C for 0–20 seconds, then switched off for 20–60 seconds. Zajonc found that hedonic reactions to pure sucrose, sucrose / quinine mixture, or distilled water were not altered by hypothalamic cooling or heating. Confluence model Zajonc, along with Greg Markus, developed the Confluence Model (1975), which provided a mathematical model of the effect of birth order and family size on IQ scores quantifying the relationship between in-family dynamics variability and intellectual ability. In forming this quantitative value, the confluence forms an averages of the absolute intellectual capacities of the entire family environment. As families increase in size, the overall IQ of the family drops; children from larger families do have slightly lower IQs. The last child in the family is denied the opportunity to tutor younger children, and there is a slight "extra" detriment for being the youngest child in a family. These effects are theoretically important, but the size of the effects is fairly small (amounting to a range of about 3 IQ points), thus, birth order is not an absolute determining factor for IQ although its influence is apparent. The capacity to which IQ is birth-order dependent was challenged by Wichman, Rodgers, and MacCallum (2006) whom claim that the observed differences were a product of between-family differences instead. Zajonc argued that this perceived conclusion as based on them incorrectly treating birth-order effects to parallel a linear relationship, in addition to shortcomings in the methods they progressed such as implementing the use of unfocused tests causing significantly significant trends to remain unrecognized. A study by Bjerkedal et al. (in press) offers support to the with-in family nature of the phenomena through its own findings showing that increasing birth rank paralleled a decline in IQ in a sample of 127,902 Norwegian same-family siblings. Sensory interaction on non-human animals Zajonc wanted to test the sensory interaction hypothesis, that a stimulus response not only depends on the intensity but also depends on other aspects of the condition. For