Spencer told the Institute of Directors in Auckland a series of factors "may be reducing the leverage monetary policy has over inflation."
He said the bank's flexible inflation targeting approach is becoming more flexible and relatively more weight is being attached to "output, employment, and financial stability."
While he painted different scenarios where both rate cuts and rate hikes might be necessary, he said the central bank is now "assuming greater persistence in low global inflation" and that is contributing to its current flat interest rate track.
The central bank's latest forecast show it doesn't expect to raise rates until mid-2019 at the earliest.
Tim Kelleher, head of institutional foreign exchange sales at ASB Bank, said all the speech did was highlight the bank is "trying to be flexible."
Westpac Bank senior economist Satish Ranchhod said the speech did confirm an "on hold" bias from the RBNZ.
"Even with inflation lingering below 2 per cent, they are not in a rush to cut rates and are aware of the longer-term risks for activity if they did cut. That could also have added to the upside pressure on NZD," he said.
Looking ahead, Kelleher said the kiwi could test 69.50 US cents or 70.00 cents and the GlobalDairyTrade auction overnight tonight could help as prices are expected to rise on the back of an increased threat of drought in New Zealand.
The kiwi held steady against the Australian dollar, trading at 90.21 Australian cents from 90.18 cents yesterday after the Reserve Bank of Australia kept its cash rate target at a record low of 1.5 per cent.
The New Zealand dollar was at 51.19 British pence from 50.90 pence yesterday and at 58.05 euro cents from 57.78 cents. It was at 77.56 yen from 77.31 yen and rose to 4.5579 yuan from 4.5352 yuan.
New Zealand's two-year swap rate rose 2 basis points to 2.15 while the 10-year swap rate rose 3 basis points to 3.11 per cent.
