Shares of Synaptics Inc. SYNA dropped more than 12% in the extended session Wednesday after the maker of human- interface hardware and software such as touchpads reported fiscal third-quarter adjusted earnings and revenue above Wall Street expectations, but called for a weaker current quarter due to “the currrent economic slowdown.” Synaptics earned $10.4 million, or 26 cents a share, compared with $65 million, or $1.59 a share, in the year-ago quarter. Adjusted for one-time items, the company earned $1.89 a share. Revenue fell to $326.6 million, from $400 million a year ago. Analysts polled by FactSet expected Synaptics…