Is psychology a true science and why?

A true science uses experimental methods, in order to understand observable phenomena. This is true of psychology. A true science employs quantitative methods in order to reveal non-obvious relationships among observable phenomena. This is also true of psychology. A true science seeks understanding of observable phenomena in the service of prediction and control. Again, this is true of psychology.

The notion that there are "hard" sciences like physics and chemistry that are superior to the so-called "soft" sciences (usually referring to Social Sciences) assumes that "hard sciences" are more exacting and reliable than "soft sciences." Although it is true that prediction and control are far easier to achieve when physics or chemistry are applied to the ordinary phenomena of everyday life, review articles have demonstrated (using meta-analysis of well-designed experiments) that certain findings in psychology are more robust and precise than findings in sub-atomic physics. Similarly, the laws governing biochemistry in immunology (for example) can prove elusive. The apparent distinctions among sciences seem to depend more on the complexity of the variables under study than it does on any difference in applying scientific rigor.